Happy Darwin Day!

May I wish you all a very happy Darwin Day!

Charles Robert Darwin was born on 12 February 1809 at the Darwin family home, The Mount, in Shrewsbury. Today, his 205th birthday, is a day to celebrate the birth of the great naturalist, to reflect upon his life and work and raise a brimming glass to toast a remarkable man. Who can say where we would have been without him?

Charles Robert Darwin (1809-1882)

Charles Robert Darwin (1809-1882)

A Morning with the “Origin”

Last Saturday I spent a very pleasurable morning in the Cambridge University Library admiringly (and, I confess, somewhat giddily) poring over Alfred Russel Wallace’s copy of Darwin’s Origin of Species (or, to give its full title, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life), published on 24 November 1859 by John Murray of London. Arguably the most important work in the history of science, and a mere abstract of the larger volume which Darwin had intended to publish expounding his theory of evolution entitled Natural Selection, it was with a palpable thrill that I removed the tome from its green, cardboard case, and appraised it in my hands. A stout volume of roughly five-hundred pages, bound in dark green cloth, gilt lettering on the spine, it was a treasure to behold.

I recently read the Origin for the second time, enjoying it and extracting from it even more than I had the first. It is simply a terrific book. The fertility of Darwin’s thought, the range of subjects discussed from selective breeding to palaeontology to biogeography to systematics to anatomy to embryology, the amount and variety of evidence marshaled (and the greater amount which Darwin admitted to simply having to omit for want of time and space), the quality of the argumentation, the philosophical sophistication (even if certain of Darwin’s self-deprecatory remarks may have led you to think otherwise, don’t think him a dullard!) and clear, sometimes beautiful, prose make reading the Origin for the most part a delight. It is apparent that the work presents the foundations of a ‘revolution’ in biology, the inauguration of a new ‘paradigm’, to use Kuhn’s ambiguous and disputed terminology.

Lifting the cover of the celebrated work to reveal the inner page, one reads an ink inscription in fine, cursive hand: ‘From the author’. The hand was not Darwin’s, but most likely that of a staff member of the publishers John Murray, from where it is thought that the book was sent to Wallace.  Above this inscription is Wallace’s signature: ‘Alfred R. Wallace’, and below it a third inscription, also in Wallace’s hand: ‘Ricardo Spruce from A. R. Wallace’.

On the verso opposite the title page, Wallace had made a number of inscriptions on  points relating to passages on various numbered pages of the book. One which struck me was the following brief note: ‘The origin of the eye well illustrated p.189‘. For the organ which Paley had argued in his Natural Theology could only have been the handiwork of an intelligent designer Darwin had canvassed an evolutionary account of its origination, reckoning that over numerous generations a complex camera eye, consisting of a suite of intricately interacting components, could be formed from a thin layer of light-sensitive tissue. Given many years over which many generations of a population would be subject to the sorting hand of selection, those organisms with slightly better eyes being more likely to survive and reproduce and bequeath their adaptive characteristics to their offspring, such an organ of ‘extreme perfection and complication’, to use Darwin’s words, as the eye could have been designed by an unintelligent, unintentional, unconscious process. Darwin and Wallace both independently discovered this elegantly simple explanation of the organized complexity which saturates the biosphere.

Some of the most interesting of Wallace’s inscriptions appear on pages 82-86, where Wallace had struck through the phrase ‘natural selection’ with an ink pen and written neatly in its place Herbert Spencer’s phrase ‘survival of the fittest’. Spencer had introduced the phrase, now regarded as the slogan of the odious and ill-named laissez-faire ideology of ‘Social Darwinism’, in 1864 in his Principles of Biology. Wallace thought the phrase clearer and far less apt to mislead than Darwin’s own ‘natural selection’. In a letter to Darwin written in 1866 Wallace, despairing, wrote,

I have been so repeatedly struck by the utter inability of numbers of intelligent persons to see clearly or at all, the self acting & necessary effects of Nat Selection, that I am led to conclude that the term itself & your mode of illustrating it, however clear & beautiful to many of us are yet not the best adapted to impress it on the general naturalist public.

Wallace offered his diagnosis of the problem:

Now I think this arises almost entirely from your choice of the term “Nat. Selection” & so constantly comparing it in its effects, to Man’s selection, and also to your so frequently personifying Nature as “selecting” as “preferring” as “seeking only the good of the species” &c. &c.

Wallace acknowledged that to those ‘few’ who understood Darwin’s message his words were ‘as clear as daylight, & beautifully suggestive’, but regretted that ‘to many it is evidently a stumbling block’, and so proffered the following remedy:

I wish therefore to suggest to you the possibility of entirely avoiding this source of misconception in your great work, (if not now too late) & also in any future editions of the “Origin”, and I think it may be done without difficulty & very effectually by adopting Spencer’s term (which he generally uses in preference to Nat. Selection) viz. “Survival of the fittest.”

Wallace reasoned that Spencer’s phrase is ‘the plain expression of the facts‘ of the differential survival of organisms within a population due to some being better adapted to the conditions of their environment than others and that, by contrast, the phrase ‘Nat. selection is a metaphorical expression of it—and to a certain degree indirect & incorrect, since, even personifying Nature, she does not so much select special variations, as exterminate the most unfavourable ones.’

Darwin replied that he ‘fully agree[d] with all that you say on the advantages of H. Spencer’s excellent expression of “the survival of the fittest”.’ Darwin wrote that ‘I formerly thought, probably in an exaggerated degree, that it was a great advantage to bring into connection natural & artificial selection; this indeed led me to use a term in common, and I still think it some advantage.’ He bemoaned that he had not received Wallace’s letter two months earlier, as he said he would then have made substitutions of the phrase in the fourth edition of the Origin (published in November 1866), but added that he would use the phrase in The Variation of Animals and Plants Under Domestication, which was then in preparation. He admitted, in opposition, however, that ‘The term Natural selection has now been so largely used abroad & at home that I doubt whether it could be given up, & with all its faults I should be sorry to see the attempt made,’ surmising that ‘Whether it will be rejected must now depend “on the survival of the fittest”.’ Darwin’s term was the superior competitor, winning out in the terminological struggle for existence. Spencer’s phrase has invited its own misunderstandings about the theory of natural selection, including the tired objection that the theory is tautological, making an assertion (so runs the misconstrual) about the effects on a population of the survival of its fittest members and then circularly  defining those members as those that survive. Insofar as ‘the survival of the fittest’ does capture the principle of natural selection, the ‘fittest’ are not defined as ‘those that survive’, but as ‘those that are most likely to survive’, given their overall adaptedness to their environmental conditions.

Hurtling from the fourth chapter (on ‘Natural selection’), containing the pages in which Wallace had made his textual alterations, to the final page of the book, one finds further markings by Wallace. Following a recapitulation of his ‘long argument’ in the final chapter, Darwin composes a climactic, and beautifully poetic, passage to conclude his work. Allaying a belief that the vision of the history of life on earth he had presented was one bleak and dark, of ‘Nature, red in tooth and claw’, Darwin drew a more positive picture:

Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

Wallace had marked this passage with a pencilled line in the margin and above it, written horizontally along the margin, a single apposite exclamation:


This is a worthy summation of a work which eventuated a revolution in science and a transformation of human thought in general. It was a delight to linger over an item of such significance and historical illustriousness. How splendid and precious a thing a book can be.

Debating Darwin and Design: Science or Creationism? (8) – Francis Smallwood’s Fourth Response

Debating Darwin and Design

A dialogue between two Christians


Is Intelligent Design science or ‘creationism in a cheap tuxedo’?

8th November 2013

Francis Smallwood - Fourth response

I am delighted that Joshua and I have resumed our dialogue after an unwittingly protracted hiatus of some twenty months. Whilst we were both fairly appalled by the length of time which has elapsed since our last responses, the intermission has allowed us to think, read and talk more and so we shall (hopefully) be clearer now on a few matters. My own views have changed and developed regarding certain issues, and I hope to be able to offer some more cogent and substantive arguments than some of those I have previously propounded. I look forward to continuing this interesting and multifarious debate with Joshua, a great friend, uniting as it does ‘the two greatest and purest pleasures of human life, study and society.’[1]

Introduction and overview

When Joshua and I were planning this discussion we decided that we would begin with the question with which we are currently concerned, a question which attracts a great deal of attention in the debate over ID, even though it is not the case that ID must be science or creationism as it could be neither. Joshua considered that ‘Perhaps we have gone about this discussion the wrong way round, choosing to debate the classification of ID before the merits of ID,’ adding, ‘I don’t see that it really matters.’[2] I am inclined to think that it does matter, as in asking whether or not ID is science we are presupposing that we know what claims ID makes, which I shall argue we do not. As Sahotra Sarkar remarks, ‘before we can fruitfully discuss whether ID is science or not, we need a positive account of what design and intelligence are.’[3] ID theorists have so far failed to provide such an account.

In Joshua’s previous response he helpfully précised the discussion so far and enumerated seven ‘lines of attack’ taken by critics of ID to argue that it is not science. I shall reproduce Joshua’s list here for convenience:

  1. By showing that design and creation, as concepts, are necessarily synonymous.
  2. By showing that, historically, ID emerged from the same source as creationism.
  3. By bringing up the infamous Dover trial.
  4. By showing that ID proponents are religiously motivated.
  5. By showing that ID theorists don’t publish their work in peer-reviewed journals.
  6. By showing that methodological naturalism (MN) is an essential part of science. This includes the prohibition of supernatural causation. ID necessarily has theological implications and thus violates the principle of MN.
  7. By showing that ID doesn’t follow ‘the scientific method’ and is neither falsifiable nor verifiable.

Of these, I do not believe that (1) through (5) offer legitimate means of denying ID scientific status, although, regarding (5), if ID represents the scientific breakthrough which its proponents claim it does, then it is surely surprising that the majority of the scientific community should have failed to appreciate its import and treated the theory with such manifest disdain. Regarding (6), methodological naturalism (the view that when doing science we should seek only explanations which refer to natural, law-governed causes), I shall argue, is essential to modern science. Inasmuch as ID flouts this principle, it is at variance with the rest of modern science, giving us a reason to deny that ID is science. Regarding (7), whilst there is an undeniable difference between science and other modes of inquiry (e.g., history, philosophy, theology, etc.) a successful demarcation criterion has—and not for want of effort—so far eluded philosophers of science. Both verifiability and falsifiability have been shown to be beset with problems and whilst testability is a stronger candidate criterion it is similarly problematic. I shall argue that, assuming that the notion of ‘intelligent design’ is intelligible (which I shall go on to argue that it is not), ID is untestable, contrary to the claims of ID theorists, since we lack auxiliary information about the goals and abilities of the designer which is required to conjoin with the design hypothesis to derive observational implications. I shall not, however, from this conclude that ID is not science since it is conceivable that this information may become available. One could not justifiably claim that this information could never become available without foreknowledge of future inquiry.

Whatever objections may be raised against ID in relation to naturalism and demarcation criteria, I agree with Sarkar that disquisitions on such topics are controversial, and that because of their controversiality they are liable to obscure the deeper problems with ID, allowing its proponents to ‘camouflage the basic incoherence of their claims.’[4] According to Sarkar, ID is not science ‘mainly because we simply do not know what it is saying.’[5] The real problem with ID is its theoretical indigence. Given the lack of positive theory, it is hardly surprising that ID is untestable, predictively (or retrodictively) infertile and explanatorily impotent. ID ultimately founders on account of its insubstantiality. ID is not a rival theory to Darwinism (a term which I shall use interchangeably with ‘evolutionary theory’[6]) simply because there is barely any theory at all—only a rehashing of the old argument from design[7] shorn of its explicitly theological content, couched in information-theoretic terms and applied to biochemistry.[8] ID theorists gleefully pronounce the demise of Darwinism on account of its unsolved problems and enjoin that it be abandoned and ID embraced, even though we have not been told what exactly ID theory is or given any reason to think that it offers a better alternative. To think of substituting the vapid offerings of ID theorists for as vigorous a theory as Darwinism is absolutely unconscionable.

Until its concepts are defined with a precision beyond that bequeathed by ideas from natural theology and its arguments predicated on a firmer basis than dubious analogies with human intelligent agency, ID cannot be considered science. But if ID is not science is it creationism? I am willing to accept that there is a conceptual distinction between ‘creation’ and ‘design’ and so shall conclude that, we simply do not know whether or not ID is creationism since ID theorists refuse to elaborate on how the Intelligent Designer is supposed to go about his business, its agency having never been observed.

The extra- and intra-scientific importance of the question of ID’s scientific credentials

Whilst it may be that we should perhaps have started with another question than that of whether or not ID is science, the question is still important and worth consideration. Science, unquestionably one of the greatest achievements of our species, is invested with tremendous authority within modern western culture, and so the conferment of scientific status upon ID has numerous extra-scientific implications, particularly in the educational sphere. Larry Laudan has remarked that ‘the value-loaded character of the term “science” (and its cognates) in our culture should make us realize that the labeling of a certain activity as “scientific” or “unscientific” has social and political ramifications which go well beyond the taxonomic task of sorting beliefs into two piles.’[9] Even if determining whether ID is science is merely an exercise in intellectual taxonomy, it is an exercise with serious implications.[10]

But it is not just the extra­-scientific implications of the question which demand its consideration; the question has significant implications for science itself as the classification of ID as science would entail the dispensation of methodological naturalism which is one of the defining characteristics of modern science. The inference which ID makes from natural effects to a supernatural cause is at variance with modern scientific practice. As Sarkar writes, ‘naturalism is central to the pursuit of science.’[11] He concedes that ‘it is legitimate to argue that science may change to embrace strategies beyond methodological naturalism [the view that science is neutral regarding the existence of supernatural entities and that scientific explanations should be naturalistic] but that will require changes as drastic as the conceptual revolutions [of Newtonian mechanics, general relativity, quantum mechanics and natural selection]’.[12] I would argue that the relinquishment of methodological naturalism would require changes of a different order to those precipitated by these conceptual revolutions, for, and as Sarkar notes, all of these conceptual revolutions have accorded with methodological naturalism. The development of science has seen the gradual displacement of supernaturalistic explanations by naturalistic explanations. Whilst supernaturalistic explanations were once permitted within science, they now no longer are. Philip Kitcher refers to intelligent design as ‘dead science’, ‘a doctrine that once had its day in scientific inquiry and discussion, but that has rightly been discarded.’[13] It is also worth noting that when intelligent design was a living science it was explicitly theistic. ID seeks to revivify its inhumed carcass and yet remove the theistic flesh which legitimised it.

Why the intelligent designer must be a supernatural being

Many ID theorists, Joshua included, are theists of a Christian variety who identify the intelligent designer as God—that is, these theists believe that the cause of designed structures is supernatural. However, ID theorists maintain that, whilst this may be, the Designer need not be supernatural.[14] Behe has said that ID theorists ‘simply focus on the observation of design’[15] and that ‘the identity of the designer will be ignored by science.’[16] It is therefore held that the Designer could be a natural entity, an alien of some kind, thereby allowing ID theorists to deny its inconsistency with methodological naturalism. However, whilst this may be, one is then confronted with the question, whence the natural Designer: either the natural Designer evolved (most plausibly by some Darwinian process[17]) or was the product of design or some combination of the two. As the designer of ICSs, the natural Designer would, being significantly more complex than its products, also contain at least one ICS which, according to ID, cannot evolve and so must be the product of design. This being so, and since there can be no infinite regress of natural designers due to the finiteness of the universe, the Designer must be supernatural.[18] If it is necessarily the case, then, that the intelligent cause inferred by ID theorists is supernatural, ID is inconsistent with methodological naturalism. If methodological naturalism is essential to science, then ID cannot be considered science.

The inconsistency of ID with methodological naturalism

Dembski admits that ‘So long as methodological naturalism sets the ground rules for how the game of science is to be played, intelligent design has no chance of success.’ His solution: ‘dump methodological naturalism.’[19] He contends that ‘design should be readmitted to full scientific status.’[20] Yet the fulfilment of this solicitation would amount to the rejection of modern science and the palingenesis of ‘dead science’. Some ID proponents complain that the inclusion of naturalism within a definition of science is arbitrary. One should, however, distinguish between descriptive and stipulative definitions. The statement that ‘naturalism is central to the pursuit of science’ is not an arbitrary stipulation but a description of modern science.[21] Of course, the fact that naturalism is central to the pursuit of science does not mean that it should be. As Stephen Meyer rightly says, ‘The indicative does not, after all, imply the imperative.’[22] Nevertheless, there is a normative justification for the scientist’s commitment to methodological naturalism, namely, that doing so has been immensely fruitful. As Ruse exclaims, ‘Methodological naturalism works!’[23] As long as design (or some form of supernaturalistic causation) is a real possibility staunch commitment to methodological naturalism may prevent us from accessing the truth.[24] For this reason, methodological naturalism must be a revocable doctrine, yet its past success and the failure of ID theorists to offer convincing evidence of design give no reason to think its revocation due.

Unlike Ruse and others, I shall not argue that because ID is inconsistent with methodological naturalism it is therefore unscientific since it is conceivable that one day this principle of methodology, even though it has carried us so far, may have to be abandoned and design become the subject of scientific inquiry. However, ID’s inconsistency with naturalism places it at variance with the rest of science and this fact gives us a reason to deny that ID is scientific.

Testing ID against Darwinism

Joshua has asserted that ID is testable,[25] however, since ID theorists do not identify the designer, we lack information about the goals and abilities of the designer which is required to test the design hypothesis. As I said above, I shall assume that the design hypothesis is intelligible since I think that it is to an extent, but only insofar as we are prepared to rely on dubious analogies and our inheritance from the natural theological tradition. According to Sober, testing a hypothesis (i) involves probabilistic (rather than strictly deductive) relations to observations and (ii) is contrastive.[26] According with the Duhem-Quine thesis,[27] Sober writes that ‘testable theories typically do not make predictions (whether deductive or probabilistic) all by themselves but need to make use of additional auxiliary propositions.’[28] As Fitelson et al. write, ‘To test evolutionary theory against the hypothesis of intelligent design, you must know what both hypotheses predict about observables.’[29] In asking what predictions the hypotheses of ID and Darwinism make we are asking what observations we would expect to make given the truth of each of the hypotheses. In order to test[30] the hypothesis (say) that the bacterial flagellum was intelligently designed against the hypothesis that it evolved by a Darwinian process we require auxiliary assumptions about the goals and abilities of the designer for which there must be ‘independent reason’.[31] We cannot simply cook up these auxiliary propositions; rather, we must acquire them by identifying ‘auxiliary information that is independently supported.’[32] ID proponents often present a design inference as an inference to the best explanation,[33] where which of the competing candidate explanations is to be inferred is decided by a likelihood analysis. ID theorists claim that the existence of structures such as the bacterial flagellum which are ICSs or exhibit high amounts of CSI are highly improbable given Darwinism but far more probable given ID. Expressed symbolically,

Pr(bacterial flagellum | ID) >> Pr(bacterial flagellum | Darwinism).

Note that the ID theorist need not claim that the likelihood (the probability which a hypothesis confers upon an observation) of ID is far greater than the likelihood of Darwinism, as we should favour ID even if its likelihood is only slightly greater than the likelihood of Darwinism—that is,

Pr(bacterial flagellum | ID) > Pr(bacterial flagellum | Darwinism)—,

nor that ID confers an absolutely high likelihood upon the bacterial flagellum. It may be that Pr(bacterial flagellum | ID) is very low, but as long as it is higher than Pr(bacterial flagellum | Darwinism) ID should be favoured.[34] However, without auxiliary assumptions about the goals and abilities of the Designer—Is the Designer concerned with the locomotive capabilities of bacteria? Is it within his power to furnish bacteria with flagella?—we have no way of knowing whether the above comparisons are correct since we have no idea what Pr(bacterial flagellum  | ID) is.[35]

Lydia McGrew appreciates that information about the goals and abilities of the designer is ‘difficult to obtain’, but she claims that it is ‘unnecessary’ for assessing the likelihood of ID, her reason being that we regularly and unproblematically infer intelligent causation even when we have no knowledge of the identity of the putative agents and so no knowledge of their goals and abilities. For instance, when we discover an arrowhead with serrated edges or a death which is obviously not a suicide or due to natural causes we infer an intelligent cause.[36] McGrew argues that from our empirical knowledge of intelligent (human) agents producing ICSs[37] we can induce that biological ICSs were also produced by an intelligent (though non-human) agent of whom we have no empirical knowledge. Since we (correctly) infer intelligent causes of certain effects with certain properties, when confronted with certain other effects which share some of the properties of those intelligently-caused effects we can infer that those effects whose origins are under investigation were also intelligently caused. We do not know, however, if such an argument from analogy is sound, for effects which share similar properties can be due to different causes. For instance, greyhounds and cheetahs share similar properties, swiftness being one example. However, greyhounds and cheetahs are not swift for the same reasons. The swiftness of greyhounds is due to a form of ID (selective breeding), but it would be a mistake to infer from this fact that the swiftness of cheetahs is also due to ID.[38] Whilst McGrew claims that knowledge of the goals and abilities of the designer is ‘unnecessary’, it is by appealing to the goals and abilities of putative designers that we are able to determine that the causes of swiftness in greyhounds and cheetahs are different: human agents sought to breed swift greyhounds for racing and were able to do so by carrying out selective breeding programmes, whereas there were no humans around when cheetahs became swift and even if there were it is unlikely that they would have been able or wanted to make cheetahs swift. The fact that a biological system such as the irreducibly complex flagellum is similar to irreducibly complex artefacts designed by humans does not offer an indication of the likelihood of ID as we don’t know what the (non-human, supernatural) designer wants to produce or what he is capable of producing since we have no empirical knowledge of the designer. Contra McGrew, it cannot simply be assumed that a putative designer would be like human designers.[39] As long as we do not know what the intelligent designer would make, we cannot test the hypothesis that a biological system was intelligently designed.[40] At some future time we may acquire the requisite auxiliary information which would enable us to answer questions about the goals and abilities of the designer and determine the likelihood of ID. Until then, however, these questions must go unanswered. Until they are answered ID cannot be tested against Darwinism. It must be noted, however, that this does not mean that ID must always remain untestable, as that would require ‘considerable knowledge about what the future of inquiry may bring.’[41]

Despite the allure testability has held for demarcationists, it cannot provide a successful demarcating criterion. If it were adjudged that a theory which currently cannot be tested cannot be science because it is untestable, then had such adjudications been made in the past many successful scientific theories would have been rejected in their inchoate stages as unscientific since it is unlikely that the rudimentary formulations of scientific theories will yield testable predictions.

The real problem with ID

I have tried to show that attempts to dismiss ID by claiming that it is not science through the deployment of demarcation criteria are unsuccessful. Not only are they unsuccessful, they create a smokescreen of philosophical controversy behind which the real problem with ID remains hidden.

Sarkar writes that ‘to be science, a doctrine must make substantive claims though making such claims does not by itself confer scientific status.’ Sarkar notes that ‘Making substantive claims is not a demarcation criterion,’ but rather ‘an adequacy test for a science’—a test which ID ‘fails’.[42] Whilst the ID literature is saturated with negative argumentation there is a striking paucity of positive argumentation. The positive theory of ID boils down to the unilluminating claim that certain structures are the result of intelligent causation. As Sarkar notes, ‘if we add the claim that the designer is a conscious physical entity, the natural reaction should be to regard ID as coherent but with no evidence whatsoever to support it and all evidence against.’[43] However, given that the designer must be a supernatural entity, as I have argued, ‘we no longer have any clue what “intelligence” means.’[44] ID is not science because we are unable to make sense of the smidgeon of positive theory which ID proponents do offer without relying upon dubious analogies and ideas inherited from the natural theological tradition.

Sarkar willingly concedes that ID may have a future, given the possibility that the concept of design may be precisely specified and empirically anchored,[45] but that ‘at present ID is not yet science simply because we have no such (substantive, rather than metaphorical) theory of ID that is comprehensible without implicit appeal to prior acquaintance with Christian theology and the metaphorical invocation of its fundamental concepts of intelligence and design.’[46] ID is not science, not because it fails to satisfy any demarcation criterion, but simply because it does not make substantive claims. The real problem with ID is its vapidity.

Creation and design

I have argued that ID is not science—but is it creationism? Both ID and creationism share significant commonalities: both ideas invoke supernatural causation, claiming that we can infer supernatural causes from natural effects and that certain aspects of the world cannot be explained in terms of natural processes. Unlike creationism, ID is not based on religious doctrine. Earlier, I used (1) to argue that ID is some form of creationism. I am willing to accept, however, following Dembski, that there is a conceptual distinction between ‘creation’ and ‘design’:[47] creation involves bringing material into being whereas design involves merely rearranging pre-existing materials.[48] According to the logic of my earlier argument I cannot now claim that ID is creationism. However, since ID theorists have failed to elaborate on how the designer brings about his designs, we should conclude that we simply do not know whether ID is creationism or not, although some day we may.


In conclusion, ID is not science. Despite the similarities between ID and creationism, we do not know whether ID is (some form of) creationism or not. Despite the outlandish claims its proponents perpetuate on its behalf, ID does not offer any insights (great or otherwise) into the origins of the living world. By contrast, Darwinism is a theory of immense explanatory power, accounting for a swathe of facts which otherwise remain disparate and unconnected. Darwin showed that the appearance of design in the living world is illusory,[49] or, alternatively—although it amounts to the same thing—that the design in the living world does not require a designer.[50] I think that ‘design-talk’ is permissible within biology[51]—that one could say that the biosphere contains designed elements—but, if so, it should be made quite clear that this design does not imply an intelligent designer: if the living world exhibits design, then it must be there are non-intelligent design processes as well as intelligent design processes. With his discovery of natural selection Darwin performed an ‘exorcism against Paley’,[52] demonstrating that design can result from a non-intelligent process which has ‘no vision, no foresight, no sight at all.’[53] Whatever the similarities between human artefacts and biological systems, their causes are quite dissimilar.


I realise that I have said rather a lot and so shall not expect Joshua to respond to each point that I have raised. I hope that I have been clear and I look forward to Joshua’s response. I am excited to be continuing with this fascinating and important conversation.

[1] David Hume, Dialogues concerning natural religion, in: Principal writings on religion including Dialogues concerning natural religion and The natural history of religion, edited with an introduction and notes by J. C. A. Gaskin, (Oxford: Oxford University Press, 2008), p.30.

[2] Joshua Gidney, Third response, ‘Debating Darwin and design: science or creationism? (7)’, available at: http://www.uncommondescent.com/intelligent-design/debating-darwin-and-design-science-or-creationism-7-joshua-gidneys-third-response/.

[3] Sahotra Sarkar, ‘The science question in intelligent design’, Synthese, 178, p.291-305, (2011), p.293.

[4] Ibid., p.304.

[5] Ibid., p.303.

[6] It could be argued that since so many thinkers and practitioners have contributed to the expansive field of evolutionary theory it would be unjust to affix to it the label of ‘Darwinism’. Whilst I can sympathise with such a sentiment, I would respond that evolutionary theory is so indebted to Darwin given the scope of his work and his astonishing prescience—just read the Origin!—that, in no way denying or downplaying the contributions of others, one can justifiably refer to evolutionary theory as ‘Darwinism’ simply because it is so manifestly the development of Darwin’s theory.

[7] The classic statement of the argument from design was given by Archdeacon Reverend William Paley in his Natural theology; or, evidence of the existence and attributes of the Deity, (London: Faulkner, 1802).  Paley argued that adaptations such as the eye, composed of numerous parts which interact to perform a function, are so exquisitely structured that they are unmistakably the handiwork of a benevolent God. ID makes no such explicitly theological claims, however there is an obvious filial relation between the two ideas. Michael Behe’s arguments about the irreducible complexity of certain biomolecular structures, such as the bacterial flagellum, bear an obvious semblance the arguments of Paley.

[8] William Dembski writes that biochemistry provides ‘the causal backdrop against which design in biology must be decided’ (Intelligent design: the bridge between science & theology, [Downers Grove, IL: InterVarsity Press, 1999], p.14).

[9] Larry Laudan, ‘The demise of the demarcation problem’, in: Physics, philosophy and psychoanalysis, p.111-27, edited by R. S. Cohen and Larry Laudan, (Dordrecht: Reidel, 1983), reprinted in: But is it science?: the philosophical question in the creation-evolution controversy, p.337-350, edited by Michael Ruse, (Amherst, NY: Prometheus Books, 1996), p.345.

[10] But, then, perhaps we should simply ignore the question? Laudan has rightly observed that ‘demarcation criteria are typically used as machines de geurre in a polemical battle between rival camps,’ opining that ‘If we would stand up and be counted on the side of reason, we ought to drop terms like “pseudo-science” and “unscientific”… [since] they are just hollow phrases which do only emotive work for us,’ insisting that ‘our focus should be squarely on the empirical and conceptual credentials for claims about the world’ (ibid., p.349). I agree with the spirit of Laudan’s remarks but I would not go so far as to pronounce matters of nomenclature ‘irrelevant,’ (ibid.) as, whilst not always clear, there are differences in patterns and standards of reasoning in different modes of inquiry which should be respected.

[11] Sahotra Sarkar, Doubting Darwin: creationist designs on evolution, (Malden, MA/Oxford: Blackwell), p.163.

[12] Ibid.

[13] Philip Kitcher, Living with Darwin: evolution, design, and the future of faith, (New York, NY: Oxford University Press, 2007), p.8. Kitcher accepts that ‘If intelligent design is no longer science, it once was, and many scientific achievements we acknowledge build upon work that it inspired’ (p.12).

[14] It should be noted that there are ID proponents who are not theists and who do not believe the intelligent designer to be a supernatural being.

[15] Michael Behe, in conversation with John Sutherland, ‘A design for life’, Guardian, 12 September, (2005), available at: http://www.guardian.co.uk/science/2005/sep/12/religion.news&gt.

[16] Michael Behe, Darwin’s black box: the biochemical challenge to evolution, (New York: Touchstone, 1998), p.251.

[17] Richard Dawkins has argued that Darwinism is probably a universal principle in his paper ‘Universal Darwinism’, in: D. S. Bendall (ed.), Evolution from molecules to men, p.403-25, (Cambridge: Cambridge University Press). I am inclined to agree with him.

[18] I presented a version of this argument in an earlier response to Joshua (Second response, ‘Debating Darwin and design: science or creationism (1)’, fn.23., available at http://musingsofscience.wordpress.com/2011/11/02/debating-darwin-and-design-science-or-creationism-4-2/). Elliott Sober had already presented an argument similar to mine which reaches the same conclusion—that the Intelligent Designer must be supernatural—although unbeknownst to me as I had not then read his paper ‘Intelligent Design theory and the supernatural—the “God or extra-terrestrials” reply’, Faith and Philosophy, 24 (1): 72-82, (2007), available at: http://sober.philosophy.wisc.edu/selected-papers. Sober argues that we have reason to believe, independent of the veracity of ID, that minds in nature are irreducibly complex, that the universe is finitely old and that causes precede their effects. Given these propositions, if minds in nature are irreducibly complex then they must be the product of intelligent design, but since the universe is finitely old and causes precede their effects there cannot be an infinite regress of natural designers and so the Intelligent Designer must be supernatural. Sober also concludes that Darwinism is neutral on the question of the existence of supernatural entities.

[19] Dembski, Intelligent design, p.119.

[20] Ibid., p.123.

[21] In defence of his claim that science is ‘an enterprise formed through the practice of methodological naturalism’, Michael Ruse writes, ‘What I am trying to do is to offer a lexical definition: that is to say, I am trying to characterize the use of the term “science.” And my suggestion is simply that what we mean by the word “science” in general usage is something that does not make reference to God and so forth, but which is marked by methodological naturalism’ (‘Methodological naturalism under attack’, in: Intelligent design creationism and its critics, p.363-85, edited by Robert T. Pennock, [Cambridge, MA/London: The MIT Press, 2001], p.371).

[22] Stephen Meyer, ‘The methodological equivalence of design & descent: can there be a scientific “theory of creation”?’, in: J. P. Moreland (ed.),  The creation hypothesis: scientific evidence for an intelligent designer, chap.2, p.67-112, (Downers Grove, IL: InterVarsity Press, 1994).

[23] Michael Ruse, Darwinism and its discontents, (Cambridge: Cambridge University Press, 2008), p.48.

[24] As Del Ratszch writes, ‘if it should turn out that some things in nature are deliberately designed and can only be correctly understood in design terms, then a human edict that deliberate design is a scientifically forbidden concept will inevitably drive our scientific investigation, in that area, into either error or failure’ (‘There is a place for intelligent design in the philosophy of biology: intelligent design in (philosophy of) biology: some legitimate roles’, in: Contemporary debates in philosophy of biology, chap.19, edited by Francisco J. Ayala and Robert Arp, [Chichester: Wiley-Blackwell, 2010], p.346-7).

[25] Joshua Gidney, ‘Debating Darwin and Design: science or creationism? (1)’ Opening, available at: http://www.uncommondescent.com/philosophy/debating-darwin-and-design-science-or-creationism-1/.

[26] Elliott Sober, Evidence and evolution: the logic behind the theory, (Cambridge: Cambridge University Press, 2008), p.152.

[27] The Duhem-Quine thesis derives its name from the French physicist and philosopher of science Pierre Duhem and the American philosopher W.V.O. Quine. According to the thesis, scientific hypotheses do not make predictions independently; rather, auxiliary hypotheses are required in order for test implications to be derived from a theory.

[28] Elliott Sober, Evidence and evolution: the logic behind the theory, (Cambridge: Cambridge University Press, 2008), p.148. This point was also made by Carl Hempel in his classic work Philosophy of natural science, (Englewood Cliffs, NJ: Prentice-Hall, Inc., 1966), p.31.

[29] Branden Fitelson, Christopher Stephens and Elliott Sober, ‘How not to detect design—critical notice: William A. Dembski, The design inference’, in: Intelligent design creationism and its critics, p.597-615, p.613.

[30] Sober writes that ‘testing a proposition often involves probabilistic rather than deductive relations to observations and that the concept of testing needs to be understood contrastively’ (Evidence and evolution, p.152). According to Sober,

Hypothesis H1 can now be tested against hypothesis H2 if and only if there exist true auxiliary assumptions A and an observation statement O such that (i) Pr(H1|O&A) ≠ Pr(H2|O&A) (ii) we now are justified in believing A, and (iii) the justification we have for believing A does not depend on believing that H1 is true or that H2 is true and also does not depend on believing that O is true (or that it is false). (ibid.)

[31] Ibid., p.144.

[32] Ibid., p.168.

[33] Peter Lipton in his seminal book Inference to the best explanation (second edition, [London: Routledge, 2004]) presented a lucid and perspicacious elaboration of the inferential procedure.

[34] As Sober says, ‘don’t ask whether the hypothesis says that the outcome was probable or improbable. The relevant question is whether the outcome is more probable according to one hypothesis than it is according to another’ (‘Testability’, p.57).

[35] We do not need to know the precise probabilistic values for each of the likelihoods; we only need to know how the probabilities compare (cf. Sober, ‘Testability’, p.58). But since we have no idea what Pr(bacterial flagellum | ID) could be, we do not know how the likelihoods compare.

[36] Lydia McGrew, ‘Testability, likelihoods and design’, Philo, 7 (1): 5-21, (2004), available at: http://www.lydiamcgrew.com/Philosophicalwork.htm.

[37] Incidentally, the mousetrap is not an example of an ICS, as has been pointed out in many criticisms of Behe’s discussions of irreducible complexity.

[38] This example is due to Daniel Dennett (cf. Darwin’s dangerous idea: evolution and the meanings of life, [London: Penguin Books, 1996], p.318) and is also discussed by Sober (cf. ‘Testability, p.63-4).

[39] McGrew writes that ‘It is arbitrary to require special hesitation in applying data from a known group to an unknown group in biological arguments for design… Perhaps we have reason to believe that [the intelligent designer] would be more powerful or more intelligent than humans, would possess a different kind of body from humans, or might even be disembodied. [If my argument that the intelligent designer must be supernatural is sound, then we can suppose that the designer is disembodied.] But even granting the probability of such differences, it does not follow that such an agent would differ from humans in inclination or ability to make machines’ (‘Testability, likelihoods and design’, my italics). Whilst it does not follow than the intelligent designer would differ from humans in inclination or ability to make machines, we cannot suppose that it does not.

[40] Cf. Sober, ‘Testability’, p.64.

[41] Sober, Evidence and evolution, p.149.

[42] Sarkar, ‘The science question in intelligent design’, p.293.

[43] Ibid., p.303.

[44] Ibid.

[45] Sarkar writes that ‘because we have the intuitively reasonable idea that design means conforming to a target, we can imagine that the concept of CSI can eventually be characterized sufficiently precisely, perhaps even operationalized, and connected to the empirical world. We should not forget that the development of many sciences followed this pattern of gradual clarification of concepts over time’ (‘The science question in intelligent design’, p.301).

[46] Ibid., p.302.

[47] It is worth noting however that Stephen Meyer does not seem to think that there is a conceptual distinction as he treats the terms ‘design’ and ‘creation’ synonymously (cf. ‘Is intelligent design science?’).

[48] Dembski writes that ‘Creation is always about the source of being of the world. Intelligent design, as the science that studies signs of intelligence, is about arrangements of preexisting materials that point to a designing intelligence. Creation and intelligent design are therefore quite different. One can have creation without intelligent design and intelligent design without creation’ (‘Intelligent design’, available at: http://www.designinference.com/documents/2003.08.Encyc_of_Relig.htm).

[49] Richard Dawkins coined the term ‘designoid’ (pronounced ‘design-oid’) to designate structures which ‘look designed, so much so that some people—probably, alas, most people—think that they are designed’ (Climbing Mount Improbable, [London: Penguin Books, 2006], p.4).

[50] Cf. Francisco J. Ayala, ‘Darwin’s greatest discovery: design without a designer’, Proceedings of the National Academy of Science of the United States of America, 104, p.8567-73, (2007).

[51] Daniel Dennett has argued strenuously for the retention of ‘design-talk’ within biology (cf. Darwin’s dangerous idea, [London: Penguin Books, 1996]).

[52] Simon Conway Morris, ‘(Re) Reading the Origin’, Current Biology, 19 (3), R103, (2009).

[53] Richard Dawkins, The blind watchmaker, (London: Penguin Books, 1988), p.5.

Debating Darwin and Design: Science or Creationism? (7) – Joshua Gidney’s Third Response

As some of you reading this may know, my good and estimable friend Joshua Gidney and I are conducting a discussion on Intelligent Design and Darwinism in which we hope to defend the views which we espouse–Joshua espousing the former and I the latter–but also to explore and develop our views; in short, to have a constructive debate. We have posted our responses to one another intermittently over the last few years when we have been able to do so. Quite unwittingly, this freedom to respond whenever we choose resulted in an interminably protracted hiatus lasting some twenty months. After meeting together, however, pepped by red wine, coffee and cake, we resolved to resume our discussion–and so we have! Below is Joshua’s third response to me. My fourth response will hopefully follow shortly.

Debating Darwin and Design

A dialogue between two Christians


Is Intelligent Design science or ‘creationism in a cheap tuxedo’?

12th September 2013

Joshua Gidney – Third Response

One of the many benefits of taking part in a written dialogue, like this one, is that there are no time constraints. Francis and I have initiated this discussion ourselves, and so we are free to respond when we wish to. Unfortunately this has resulted in an eye-watering one year and eight months between the last instalment, and now. This is an atrocity and I am to blame. Shortly after my guilty conscience overwhelmed me, several glasses of wine, a cup of coffee, and some delightful walnut cake, Francis and I swore to continue our deliberations. Due to both of us having busy lives, it is inevitable that our responses will be infrequent. As I have already stated, this is not an issue (unless you’re impatient!). We are engaging with each other and that is what matters. Besides, I very much like the idea that this discussion could continue in to our old age.

In previous writings we have covered much ground, so before I respond directly to some of the points raised by Francis I would like clarify a couple of things and briefly review some of the ground we have covered. Although it would be somewhat counterproductive to keep going back and forth on the same point, at the same time I don’t wish us to end up with a bunch of loose threads.

The issue at the heart of this part of the debate is not the whether ID is true or not, but whether it is a scientific theory. If not, what is it really? Though we are both very concerned about the veracity (or lack of veracity), of the design hypothesis, we are not focussing on this at the moment. The classification of ID is what is at issue here. We will leave discussion on the merits of ID till another time. If I could successfully show that ID counts as what we would normally call a scientific theory, that would still not serve to show that it is true. It is possible for something to be scientific and false. Equally, if Francis could convincingly show that ID is essentially creationism, motivated by Christian fundamentalists wishing to establish a theocracy, this would in no way show that it is false. If one attempted to argue otherwise, one would be guilty of committing the genetic fallacy. Furthermore, only someone who holds to a scientistic worldview would hold that in order for ID to be considered true, it must fall under the umbrella of science. Neither me nor Francis subscribe to scientism and we both recognise it to be an irrational and entirely discredited philosophy of science. At the end of the day it is ‘Better to be unscientific and true than scientific and false’.1
Thomas Nagel writes: “A purely semantic classification of a hypothesis or its denial as belonging or not to science is of limited interest to someone who wants to know whether the hypothesis is true or false.”1 Arguments over the classification of ID can often just be red herrings, brought up to avoid dealing with the substance of the more important arguments. Some readers have complained that we are wasting time, arguing over an a mere exercise in taxonomy. Does this issue matter? Perhaps we have gone about this discussion the wrong way round, choosing to debate the classification of ID before the merits of ID. I don’t see that it really matters. The ‘Is it science’ issue is, I believe, an important one but we both recognise the latter issue to be of greater importance. Francis and I, like countless others, are truly enamoured by, and study, many of the sciences. We are naturally interested in the question under discussion and we don’t see it merely as an exercise in taxonomy. There is much more to life than science, but science is a huge cultural authority and there are many philosophical, sociological and educational implications that follow scientific theories. ID theorists present the theory as a scientific one and want more scientists, and the public, to view it as such. The scientific classification of ID raises important educational questions about what is included or excluded from the science class. Analytic philosopher Alvin Plantinga notes the importance of the classification of ID pointing out that it is‘’…not a merely verbal question about how a certain word is ordinarily used. It is, instead, a factual question about a multifarious and many-sided human activity — is the very nature of that activity such as to exclude ID?’’3
One more thing I wish to note is with regard to the original question under consideration. We are only using the opening question as a catalyst for further discussion. The question ‘Is Intelligent Design science or creationism in a cheap tuxedo?’, presents us with false alternatives. If it isn’t science, that doesn’t automatically mean that it is creationism. It could be a whole host of other things. Perhaps it’s neither creationism nor science? Because creationism isn’t a scientific belief, to show that ID is essentially creationism is to show it to be unscientific. However, to show ID to be unscientific is not to show that it is creationism per se. Unless, of course, some of the reasons given for why it is unscientific are the same reasons given for why it is a brand of creationism.
Francis has claimed that although ID certainly isn’t the same as young earth creationism, it does have a ‘creationistic’ flavour to it. We have both agreed that it is not fair to lump ID with creationism. In his last response, Francis did not provide any more reasons to support his belief that ID and creationism are as close as he thinks. It was not clear to me whether he was giving up on this line of critique, or merely trying to move the discussion along. I will leave that up to him to clarify.
There are, as far as I can see, seven ways by which critics attempt to argue that ID and creationism are the same (or similar), and that it shouldn’t be considered scientific:
1. By showing that design and creation, as concepts, are necessarily synonymous.
2. By showing that, historically, ID emerged from the same source as creationism.
3. By bringing up the infamous Dover trial.
4. By showing that ID proponents are religiously motivated
5. By showing that ID theorists don’t publish their work in peer-reviewed journals.
6. By showing that methodological naturalism (MN) is an essential part of science. This includes the prohibition of supernatural causation. ID necessarily has theological implications and thus violates the principle of MN.
7. By showing that ID doesn’t follow ‘the scientific method’ and is neither falsifiable nor verifiable.
There is some overlap between a few of these points but I hope they serve to clarify the discussion . Francis has not used points 2 and 5 and although he brought up 3, the Dover trial, he did not use it for the purpose of arguing that it is unscientific/creationism.
To defend point 1, Francis argued ‘What design theory identifies, therefore, is not a designer but, rather, a creator…’4 But as William Dembski explains “Creation is always about the source of being in the world. Intelligent design is about arrangements of pre-existing materials that point to a designing intelligence…One can have creation without intelligent design and intelligent design without creation.”5 ID theorists are generally very careful with making such distinctions and it is contrary to the principle of charity to suggest they are just making the distinction in order to slip it under the radar. Michael Behe explains that ‘diligence in making proper distinctions should not be impugned as craftiness.’6
Francis defended 4 by pointing out that most of the key ID theorists are Christians. He writes “…the four fathers of the ID movement—Johnson, Dembski, Behe and Meyer—are all Christians. They all, presumably, believe the intelligent designer to be the God of the Judaeo-Christian tradition, despite their insistence that this is not inferred from the detection of design.”7 I pointed out that this is an irrelevance. If an ID proponent were to adopt such bad reasoning, they could easily point out that many key neo-Darwinists are atheists. Does this not mean that neo-Darwinism is a cover for atheism? Of course not. You can’t judge a theory by the company it keeps. Again, Dembski puts it well “I might add that my views on Christian theology should be just as irrelevant for evaluating the scientific evidence I present for intelligent design as Richard Dawkins’ views on atheism are irrelevant for evaluating the scientific evidence he presents for Darwinism.”8 Furthermore, there are many ID proponents who have different religious backgrounds and. There are also atheists and agnostics within the ID movement. For more details on this, see my article: “Are these atheists and agnostics really covert creationists?”9

Points 6 and 7, it seems, are going to be where the rubber hits the road. Francis devoted the majority of his previous response to 6 and I believe this is where the meat of the discussion will lie. Although I haven’t directly responded to his points on this issue, I will in subsequent writings. For now, I just wanted to review some of the ground we have covered in order to reach a few conclusions along the way that otherwise might have been left behind. I apologise to Francis for there not being much he can respond to with regard to his last instalment, but perhaps he could distil and clarify some of his thoughts and comment on a few of the points I have brought up from our previous exchanges. It would be useful if he could point out which lines of attack, out of the seven I have outlined, he still finds legitimate and those he does not. I thought some clarification from both of us would be necessary because of the long period of time that has passed since we last wrote. I don’t want to assume that we haven’t changed our minds on anything.

I greatly look forward to continuing this spirited and substantive dialogue.


1. Williams, P.S “Intelligent Designs on Science: A Surreply to Denis Alexander’s Critique of Intelligent Design Theory”, available from http://www.arn.org/docs/williams/pw_designsonscience.htm

2. Nagel, T. “Education and Intelligent Design”, 195. Cf. Alvin Plantinga, “Whether ID Is Science Isn’t Semantics”; available from http://www.discovery.org/scripts/viewDB/index.php?command=view&id=3331.

3. Plantinga, A. “Whether ID Is Science Isn’t Semantics”; available from http://www.discovery.org/scripts/viewDB/index.php?command=view&id=3331..

4. Smallwood, F. Debating Darwin and design: science or creationism? (4), Second Response. Available at: http://musingsofscience.wordpress.com/2011/11/02/debating-darwin-and-design-science-or-creationism-4-2/

5. Dembski. W.A. The design revolution: answering the toughest questions about intelligent design. (Nottingham: Inter-varsity press, 2004). p.38.

6. Behe. M.J. ‘Whether Intelligent Design Is Science: A Response to the Court in Kitzmiller vs. Dover Area School Distric’. Available at: www.discovery.org/scripts/viewDB/filesDB-download.php?command=download&id=697, p.8.

7. Smallwood, F. Debating Darwin and design: science or creationism? (4), Second Response. Available at: http://musingsofscience.wordpress.com/2011/11/02/debating-darwin-and-design-science-or-creationism-4-2/

8. Dembski. W.A. “Coming clean” about YEC? Available at http://www.uncommondescent.com/intelligent-design/coming-clean-about-yec/

9. Gidney., J. “Are these atheists and agnostics really covert creationists?”, available from http://www.uncommondescent.com/intelligent-design/are-these-atheists-and-agnostics-really-covert-creationists/

Adaptation and Explanation

We are dealing with life when we are forced to invoke natural selection to achieve a complete explanation of an observed system.[1]

George C. Williams

Adaptation, the fit between an organism and its environment, is perhaps the most striking feature of the living world and one which demands explanation. In the introduction to the Origin of Species,[2] Darwin wrote that ‘the conclusion that each species had not been independently created, but had descended, like varieties, from other species’ would be untenable ‘until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which most justly excites our admiration.’[3] William Paley, in his Natural Theology,[4] had argued that the exquisite adaptations which pervade the organic world, such as the camera eye, were the handiwork of an intelligent designer. Darwin was in full agreement with Paley that adaptation requires special explanation but rejected Paley’s inference to a designer and argued instead that adaptations could be produced gradually and cumulatively by the natural selection of slight, successive variations.[5] Darwin offered a naturalistic explanation of adaptation, showing that the appearance of design in the organic world is only an appearance, an illusion,[6] or, alternatively (although it amounts to the same thing), he could be taken as showing that design does not require a designer.[7]

Adaptationism and the explanation of adaptation

Adaptationism is often taken as referring to a range of views about the nature of the evolutionary process and the importance of the role of selection therein, the aims of evolutionary biology and the investigation of biological systems.[8] Steven Orzack and Elliott Sober, conceive of adaptationism more narrowly, however, defining adaptationism as a single thesis about the role of selection in evolution:[9]

Natural selection is a sufficient explanation for most nonmolecular traits, and these traits are locally optimal.[10]

Stephen Jay Gould and Richard Lewontin offered a similar, though more tendentious, representation of adaptationism, claiming that ‘It is based on faith in the power of natural selection as an optimizing agent’,[11] its central tenet being ‘the near omnipotence of natural selection in forging organic design and fashioning the best among possible worlds.’[12] Adaptationism, according to Orzack and Sober, can be tested quantitatively ‘by the accumulation of successes and failures of specific optimality models.’[13] Conceiving of adaptationism in this way is problematic, however, and fails to represent much adaptationist thought. Kim Sterelny writes that he thinks ‘adaptationists are really more interested in function than in optimality.’[14] Williams evidences this when he writes that ‘Adaptation is demonstrated by observed conformity to a priori design specifications’, adding that this was ‘the main method used by Galen and Paley.’[15] What makes the heart an adaptation is not that it was produced by selection but that it performs the function of pumping blood around the body.[16]

Sterelny writes that ‘We should distinguish between what selection undisturbed would produce and good design.’[17] The optimal phenotype within a population (i.e., the fittest of the available variants within the population) may have gone to fixation, however if the available variation is limited, then the optimal phenotype may not be one which excites our admiration as, as Lewens puts it, ‘design quality may be quite awful.’[18] Selection can only work upon available variation to generate adaptation; selection does not necessarily guarantee improved adaptation. Lewontin has given an example where adaptation does not improve within a population subject to selection pressures and may actually worsen.[19] Furthermore, Sewall Wright[20] showed that selection and drift together may lead to improved adaptation by allowing populations to traverse a fitness valley on the adaptive landscape and scale a fitness peak higher than that previously occupied and which would have been inaccessible were selection acting alone.[21]

One of the infelicitous implications of Orzack and Sober’s conception of adaptation is that it divests natural selection of its explanatory power: ‘Natural selection is no explanation of adaptation, if adaptation is by definition whatever selection undisturbed produces.’[22] Many adaptationists are committed to what Tim Lewens has called ‘good-designism’,[23] the view that biological systems are well designed to perform various functions. Proponents of good-designism must be committed to more than a belief about the relative importance of selection in evolution; they must also be committed to a belief about the availability of variation upon which selection can operate, for only if there is a wide range of variants for selection to sort amongst can it be capable of generating good design. The adaptationist is committed to more than a belief about the relative importance of selection; it is therefore wrong to represent all adaptive hypotheses as optimality hypotheses.

According to Orzack and Sober, ‘Adaptationists do not deny that factors other than natural selection played some role in evolution. However, they believe that these other influences may be safely ignored.’[24] In explaining the evolution of an adaptation—that is, in explaining the functional properties of a trait—the adaptationist treats selection as a sufficient explanation. Sterelny reckons that such a view ‘gets something right about the idea behind adaptationist reasoning’, expressing an ‘adaptationist intuition… that we can “idealise away” from genetic and proximal details in explaining the origin or persistence of traits.’[25] Adaptive explanations of traits, such as (for example) the spines of xerophytic plants (e.g., cacti such as Carnegiea gigantea, the Mexican ‘Giant Saguaro’ [Figure 1]), will invoke a selective regime to explain the existence of spines: those plants with spines reduced transpiration rates and were better protected from predators and so had a higher fitness than their conspecifics lacking spines, thereby leading to an increase in the representation of genes for spines within subsequent generations and therefore an increase in the number of plants with spines. The explanation given in terms of a selective regime is regarded as sufficient to account for the origin and persistence of spines in that if there were no selection for spines then the plants would not have spines.[26]

Figure 1 Areoles of spines derived from axillary buds  in C. gigantea

Such an explanation, however, whilst it is sufficient to explain why certain desert-dwelling plants have spines, does not necessarily claim that selection was the most important causal factor in the evolution of spines or that there were no other contributing causal factors; it merely claims that there was selection for spines, without making any claims about the importance of selection relative to other factors such as genetic drift, migration or phylogenetic or developmental constraints. The explanation claims that the effects or functions of spines (e.g., reduced transpiration, protection from predation) were selectively advantageous and that this is why the plants have them. Whilst there is much information about the evolution of spines which is left out by the explanation, this does not make the explanation any less adequate. As Sterelny writes, ‘in causal explanation we neither can have nor need the whole truth. Edited highlights suffice. We need only modest claims about selection to underwrite the functional hypotheses distinctive of adaptationism’[27] (my emphasis). In order to substantiate the functional hypotheses which they propose for traits, adaptationists provide explanations which identify an aspect of the causal complex pertaining to their hypotheses. Explanations need not be complete to yield understanding: the adequacy of an explanation just depends on what it is that one wants to know.

Kinds of explanation

In their paper entitled ‘In defense of explanatory ecumenism’,[28] Frank Jackson and Philip Pettit advocate casual fundamentalism, the view that all higher-order properties are supervenient (or dependent, one might say) upon lower-order properties,[29] whilst embracing explanatory pluralism or ecumenism, the view that we should seek both lower- and higher-order explanations in order to achieve understanding of an event.

They begin by remarking upon the widespread predilection for fine-grained explanations (i.e., explanations which are highly detailed). According to those who hold the fine-grain preference, the more detail an explanation contains the better the explanation is. However, whether we should prefer explanations of a finer or coarser grain depends upon what it is that we want to know about an event. For example, if one wanted to explain the increase in crime in a city one could opt for a fine grained explanation containing information about the individuals responsible for the increase in crime rates, about their personal circumstances and the reasons they gave for perpetrating their crimes. Alternatively, one could opt for a coarse grained explanation which states that the increase in crime was due to a recent decline in employment. Both explanations would be valid but they convey different information. The first, fine grained explanation is specific, providing information about each individual criminal and the crimes they perpetrated, thereby explaining the overall increase in crime as an aggregate of those individual cases. The second, coarse grained explanation is general, citing the decline in employment as a cause of the increase in crime rate. Whilst this explanation contains far less information than the first, and whilst there may be other general causes of the increase in crime rate, this explanation tells us that even if the individual cases enumerated in the first explanation had been different, we could still expect there to have been an increase in crime rates.

Each explanation contains different modal information. The first explanation contains information which is modally contrastive, allowing one to contrast the actual world with other possible worlds, whilst the second explanation is modally comparative, allowing one to compare the actual world with other possible worlds. Whilst the first explanation tells one what caused the increase in crime within the actual world, the second explanation tells one that in other possible worlds where there is a decline in employment that one may also expect to see an increase in crime. The first (fine grained) explanation, in presenting highly detailed information about the actual world, does not contain the modally comparative information which the second (coarse grained) explanation does. Contrastive information is usually found at lower levels of grain, whilst comparative information is usually found at higher levels of grain.[30] If one wants to understand a causal history both contrastive and comparative information are valuable: There is no need to choose between one explanation or the other; both explanations are valid, and both are necessary if one wants to achieve the fullest understanding one can. One should, therefore, reject the fine-grain preference in favour of explanatory pluralism. As Jackson and Pettit remark, ‘we do not throw an explanation away just because we have access to another.’[31]  They note that ‘we can be ecumenical about explanations at different levels of grain’[32] and that whether one should prefer one form of explanation over another depends upon one’s purpose and perspective, upon what it is that one wants to know about a causal history as ‘Explanations of different levels provide complementary bodies of information on one and the same topic…’[33]

Adaptive hypotheses as robust-process explanations

Sterelny considers how Jackson and Pettit’s analysis can be brought to bear on the debate over adaptationism. Sterelny writes that ‘an adaptationism that defined itself in terms of claims about the over-riding importance of selection in the evolutionary process would be in serious trouble.’[34] He argues that adaptive hypotheses should not be regarded as actual-sequence explanations (what Jackson and Pettit refer to as ‘contrastive explanations’) of evolutionary trajectories, as in Orzack and Sober’s conception of adaptationism, but as robust-process explanations (Jackson and Pettit’s ‘comparative explanations’) which ‘claim that some aspects of an evolutionary history are insensitive to disturbance.’ According to Sterelny’s conception of adaptationism, at the heart of which lies the commitment to good-designism, adaptive hypotheses do not make claims about the relative importance of selection in an evolutionary trajectory but merely claim that the functional outcomes of a trajectory are due to selection for those outcomes. The adaptationist’s claim, then, in advancing an adaptive hypothesis, is that were we to observe evolutionary trajectories in other possible worlds which differed in various respects but in which a given selective regime obtains we could expect the trajectories to result in similar functional outcomes. To return to the earlier example, subject to similar selective regimes in arid, hostile conditions, spines may evolve as adaptations in different plant lineages. Sterelny writes that the best tests of such robust-process adaptive hypotheses ‘will be qualitative comparisons between related lineages in distinct selective regimes, and comparisons of unrelated lineages in similar regimes.’[35] If two related lineages subject to distinct selective regimes share a feature, then it may be inferred that the feature was inherited from a common ancestor and not adaptive. However, if the two lineages possess unique features which were not inherited from a common ancestor then it may be inferred that these features are adaptive and that their existence is due to the distinct selective regimes to which the lineages are subject.

Figure 2 Spines derived from stipules in E. coerulescens

Evolutionary convergence[36] is the phenomenon where similar adaptive features arise in unrelated lineages[37] and thus provides powerful support for the robustness of evolutionary trajectories, that is, given their subjection to a selective regime their insensitivity to disturbance by initial conditions. In C. gigantea areoles (clusters) of spines are derived from groups of proto-scales in axillary leaf buds, whereas the spines of euphorbs, such as Euphorbia coerulescens (Figure 2), occur in pairs as they are derived from the stipules of the leaf base. The spines of these two different species present an example of convergence, selection working on the axillary buds of cacti and the stipules of euphorbs to produce similar functional outcomes, providing confirmation of the adaptive hypothesis proposed for spines.[38] Despite the cacti and euphorb lineages charting different evolutionary trajectories, a common selective regime has resulted in similar adaptations.

If one wants to attain a full understanding of the evolution of a trait, both actual-sequence and robust-process explanations are required; the two forms of explanation are not mutually exclusive, but complementary, conveying different kinds of modal information. In treating adaptive hypotheses as actual-sequence explanations, Orzack and Sober mistakenly oppose selection to non-selective factors, whereas selection acts in concert with these factors, sorting among the variants which these factors together generate. An actual-sequence explanation of the evolution of an adaptive trait will contain information about the complex interplay of selection, drift, migration, phylogeny and development, whilst a robust-process explanation will contain only edited highlights about selection in order to account for the functional properties of the trait. Adaptationists, as Sterelny notes, in advancing their hypotheses about the adaptiveness of traits are ‘not making a simplistic claim about the relative importance of selection. Rather, the central adaptationist claim is one about the robustness of evolutionary trajectories, not the unimportance of phylogeny, drift and development.’[39] Adaptive explanations in terms of selection are not to be treated as complete, exhaustive explanations of the evolution of traits. Rather, they identify an aspect of a trait’s causal history in order to account for its functional properties.

For an adaptationist interested in the functional properties of traits adaptive explanations of traits given in terms of selective regimes are adequate for their purposes. The adaptationist’s explanation in such a case should be construed as a robust-process explanation and not as an actual-sequence explanation. As such, the fact that the adaptationist does not refer to non-selective factors in her explanation does not mean that she believes selection to be the only important causal factor in evolution or that other non-selective factors were not a part of the causal history of a trait. If the adaptationist sought an actual-sequence explanation of a trait then her explanation would contain information about selective and non-selective factors such as drift, development and phylogeny, as these are all contributing causal factors in the evolution of traits, but she would not need this information if what she sought was an (robust-process) explanation of the adaptiveness of a trait.


The error which Gould and others have made in supposing that adaptive explanations are preclusive of non-adaptive explanations is due to a misconstrual of adaptive explanations as actual-sequence explanations which has led to a mistaken insistence upon the displacement of selectionist explanations rather than a request that they be supplemented. If we want to understand the evolution of a trait then we need to utilise all of the explanatory resources at our disposal. To repeat Jackson and Pettit’s pluralist dictum, ‘we do not throw an explanation away just because we have access to another.’ Selection interacts with drift, development, migration, mutation and phylogeny to produce the myriad forms which constitute the biosphere. If we want to understand the processes which gave rise to the living world we shall require all the explanations we can muster. Whilst I would (admittedly, tentatively) be inclined to agree with Dawkins,[40] Dennett,[41] Maynard Smith[42] and others that explaining adaptation is the central task of evolutionary biology, it is by no means the only task. Gould’s vision of the evolutionary process and of evolutionary biology was characterised by a rich holism, a characteristic which would comport with a call for explanatory pluralism.

[1] George C. Williams, Adaptation and natural selection, (Princeton, NJ: Princeton University Press, 1974), p.5.

[2] Charles Darwin, On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life, (London: John Murray, 1859).

[3] Ibid., p.3.

[4] William Paley, Natural theology; or, evidences of the existence and attributes of the Deity, (London: Faulkner, 1802).

[5] It is worth reading Darwin’s summary of the principle of natural selection, in which he expresses his conviction of its power: ‘Owing to this struggle for life, any variation, however slight and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive. I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection, in order to mark its relation to man’s power of selection. We have seen that man by selection can certainly produce great results, and can adapt organic beings to his own uses, through the accumulation of slight but useful variations, given to him by the hand of Nature. But Natural Selection, as we shall hereafter see, is a power incessantly ready for action, and is as immeasurably superior to man’s feeble efforts, as the works of Nature are to those of Art’ (ibid., p.61).

Philip Kitcher has argued that in the Origin Darwin presented a novel explanatory device through the use of what Kitcher calls ‘Darwinian histories’ (The advancement of science: science without legend, objectivity without illusions, [New York, NY/Oxford: Oxford University Press, 1993], p.20). A Darwinian history is ‘a narrative which traces the successive modifications of a lineage of organisms from generation to generation in terms of various factors, most notably that of natural selection’ (p.20-21). Kitcher writes that ‘Darwinian histories provide the bases for acts of explanation’ (p.21), describing them as ‘structured texts’ which have a schematic form (p.26). The idea behind the use of Darwinian histories is that one can explain the changes in frequencies of traits within populations over generations by using various explanatory schemata which invoke various causal factors. These schemata may be employed pluralistically in that several different schemata may be deemed appropriate to a certain case or it may be that one explanatory schema, (say) a selectionist schema, is deemed more appropriate. Thus, ‘The Origin not only allows for the use of more or less ambitious notions of Darwinian history, but also covers a range of positions on the priority of selectionist explanations’ (p.30).

[6] Richard Dawkins neologised the term ‘designoid’ to refer to objects which appear as if they have been designed in his wonderful book on the cumulative power of selection Climbing mount improbable, (New York, NY: W. W. Norton & Co., 1996).

[7] See Francisco J. Ayala’s article ‘Darwin’s greatest discovery: design without a designer’, Proceedings of the National Academy of Sciences of the United States of America, 104: In the light of evolution I: Adaptation and complex design: 8567-8573, (2007).

[8] These broad distinctions in the varieties of adaptationism correspond to Peter Godfrey-Smith’s delineation of three strands of adaptationism: empirical adaptationism, the view that selection is the most important causal mechanism in evolution; explanatory adaptationism, the view that adaptation is the most salient fact of evolution, the explanation of which is the central aim of evolutionary biology and which is powerfully explained by natural selection; and methodological adaptationism, the view that approaching biological systems as adaptations offers a fruitful investigative procedure (‘Three types of adaptationism’, in: Steven Hecht Orzack and Elliott Sober, Adaptationism and optimality [Cambridge: Cambrige University Press, 2001]). Godfrey-Smith notes that the types are logically distinct—one may endorse one form of adaptationism, whilst rejecting the others. For instance, Richard Dawkins heartily advocates explanatory adaptationism (see The blind watchmaker, (London: Penguin Books, [1986] 1988) yet he rejects empirical adaptationism. Godfrey-Smith makes this point in his paper ‘Adaptationism and the power of selection’, Biology and Philosophy, 14: 181-194, (1999), p.187, providing supporting evidence in fn.10.

Tim Lewens has sub-divided Godfey-Smith’s three types and proposed an additional fourth type: epistemological optimism, the view that we are able to acquire knowledge of evolutionary histories (see his ‘Seven types of adaptationism’, Biology and Philosophy, 24: 161-182, [2009]).

[9] Their conception of adaptationism is a form of empirical adaptationism (see above note).

[10] Steven Hecht Orzack and Elliott Sober, ‘Optimality models and the test of adaptationism’, The American Naturalist, 143 (3): 361-180, (1994), p.364.

[11] Stephen Jay Gould and Richard Lewontin, ‘The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme’, Proceedings of the Royal Society of London, B, 205: 581-598, (1979), p.581.

[12] Ibid., p.584.

[13] Orzack and Sober, ‘Optimality models and the test of adaptationism’, p.365.

[14] Kim Sterelny, ‘Explanatory pluralism in evolutionary biology’, in: The evolution of agency and other essays, (Cambridge: Cambridge University Press, 2001), p.132.

[15] George C. Williams, Natural selection: domains, levels, and challenges, (New York, NY/Oxford: Oxford University Press, 1992), p.40.

[16] This definition implies, then, that it is not a necessary condition of an adaptation that it was produced by selection; there may be adaptations which were not the result of selection at all. (This point is appreciated by Gould and Lewontin in their discussion of ‘The decoupling of selection and adaptation’ in ‘The spandrels of San Marco and the Panglossian paradigm’, p.592-593.) The logical independence of selection and adaptation is most apparent in instances where selection does not lead to improved adaptation or where selection even reduces adaptation (see note 19). However, whilst it may be the case that there are adaptations which were not the result of selection, these will be infrequent and not very complex (i.e., statistically improbable). Those adaptations, such as the heart, which are complex and which bear such a powerful appearance of having been designed to perform a function can only have been produced by selection, as selection is the only inherently non-random process which could account for such a feature by the gradual accumulation of slight, successive variations. Dawkins has presented marvellous elucidations of the cumulative power of selection in The blind watchmaker, (London: Harlow, 1986) and Climbing mount improbable.

[17] Sterelny, ‘Explanatory pluralism in evolutionary biology’, p.133.

[18] Lewens, ‘Seven types of adaptationism’, p.164.

[19] Lewontin considers a population of insects in which type a mutation arises which doubles the fecundity of its bearers but which does not make resource utilisation any more effective, in which case the mutation goes to fixation within the population yet the population does not increase due to resource limitation. In this instance selection favours the mutation yet it does not lead to improved adaptation. Lewontin gives this example in his article ‘Adaptation’, Scientific American, 293 (3): 212-230, (1978), p.222-225. Gould and Lewontin cite Lewontin’s presentation of the example in another of his publications in ‘The spandrels of San Marco and the Pannglossian paradigm’, p.592.

[20] See his famous paper ‘The roles of mutation, inbreeding, crossbreeding and selection in evolution’, Proceedings of the Sixth International Congress of Genetics, 356-366.

[21] This point is appreciated by Dawkins, widely regaled as an ‘arch-adaptationist’ and ‘ultra-Darwinian’, who writes that ‘unalloyed natural selection is in a sense an anti-perfection mechanism, hugging, as it will, the tops of the low foot-hills of Wright’s landscape. A mixture of strong selection interspersed with periods of relaxation of selection and drift may be the formula for crossing the valleys to the high uplands’ (The extended phenotype: the long reach of the gene, [Oxford/New York, NY: Oxford University Press, 1983], p.40).

[22] Sterelny, ‘Explanatory pluralism in evolutionary biology’, p.133.

[23] Lewens, ‘Seven types of adaptationism’, p.164-167.

[24] Steven Hecht Orzack and Elliott Sober, ‘Optimality models and the test of adaptationism’, The American Naturalist, 143 (3): 361-180, (1994), p.364, (my emphasis).

[25] Sterelny, ‘Explanatory pluralism in evolutionary biology’, p.133.

[26] Or at least there would be no reason for them to have spines. It may be that they have spines because they inherited them from an ancestor which possessed spines and so may possess them even though no selective advantage accrues to their possession of spines. Alternatively, the spines could have arisen incidentally from selection for another trait, the genes for spines being pleiotropically related to genes for the other selected trait. It may also be the case that spines originally served a different purpose than that which they currently do due to a process of cooptation—spines may be ‘exaptations’ rather than adaptations (see Stephen Jay Gould and Elisabeth Vrba, ‘Exaptation—a missing term in the science of form’, Paleobiology, 8 [1]: 4-15, [1982]). That a trait’s current utility does not give the reason for its origination was a persistent refrain throughout Gould’s work. In his monumental work The structure of evolutionary theory (Cambridge, MA/London: The Belknap Press of Harvard University Press, 2002) which represented the culmination of his thought on evolutionary theory, Gould wrote that ‘At the most basic level, we simply cannot gain an adequate evolutionary explanation for a trait by elucidating, however elegantly, however experimentally, and however quantitatively, its contribution to the fitness of the organisms or populations in which it now resides…our understanding of how a current trait works cannot elucidate its mode of origin…’ (p.1258). It may be, then, that whilst an adaptive hypothesis may provide a legitimate explanation of the persistence of a trait and the acquisition of its current functional properties, it may not provide an explanation of the trait’s origination.

[27] Sterelny, ‘Explanatory pluralism in evolutionary biology’, p.134.

[28] Frank Jackson and Philip Pettit, ‘In defense of explanatory ecumenism’, Economics and Philosophy, 8 (1): 1-21, (1992).

[29] According to causal fundamentalism, the ‘micro’ determines the ‘macro’: ‘Fix the way things are at the micro-level, including the relevant causal relations and causal regularities that obtain there, and you will also have fixed the macro-linkages; take any two possible worlds that are indiscernible in regard to the micro-level – in regard to particulars, regularities, and the like – and, provided that they are worlds akin to ours in ontology, the two worlds will also be indiscernible in regard to the macro-level. To put the matter in semitechnical language: the macro-properties, including the causal-relational properties at the macro-level, supervene on the micro-properties’ (ibid., p.5).

[30] Ibid., p.15.

[31] Ibid., p.16.

[32] Ibid., p.16.

[33] Ibid.

[34] Sterelny, ‘Explanatory pluralism in evolutionary biology’, p.136.

[35] Ibid.

[36] Simon Conway Morris provides an excellent elaboration of the phenomenon of evolutionary convergence and marshals a wealth of evidence in support of the ubiquity of convergence in evolution in his excellent and thought-provoking book Life’s solution: inevitable humans in a lonely universe, (Cambridge: Cambridge University Press, 2003).

[37] ‘Unrelated lineages’, of course, means ‘less closely related’ and not actually unrelated, as it is the thesis of common ancestry that all lineages are descended from a single, ancient progenitor.

[38] For further examples of convergent evolution in desert-dwelling plants, as well as for details of the evolution of spines, see the Map of Life article ‘Desert plants with succulent stems’, available at: http://www.mapoflife.org/topics/topic_387_Desert-plants-with-succulent-stems/, (30 July, 2009), (accessed 22 June 2013). The Map of Life is a project headed by Conway Morris which aims to provide information on hundreds of instances of evolutionary convergence. It is a fabulous resource, one well worth perusing : http://www.mapoflife.org/index/.

[39] Sterelny, ‘Explanatory pluralism in evolutionary biology’, p.139.

[40] Dawkins proposes that those with adaptationist leanings similar to his could be labelled ‘neo-Paleyists’ or ‘transformed Paleyists’: ‘We concur with Paley that adaptive complexity demands a very special kind of explanation: either a Designer as Paley taught, or something such as natural selection that does the job of a designer. Indeed, adaptive complexity is probably the best diagnostic of the presence of life itself’ (‘Universal Darwinism’, in: D. S. Bendall, Evolution from molecules to men, [Cambridge: Cambridge University Press, 1983], p.403-425, p.404).

[41] In Darwin’s dangerous idea  (London: Penguin Books, 1996), Dennett writes that ‘the engineering perspective on biology is not merely occasionally useful, not merely a valuable option, but the obligatory organizer of all Darwinian thinking, and the primary source of its power’ (p.187), and affirms that ‘Adaptationist reasoning is not optional; it is the heart and soul of evolutionary biology’ (p.238).

[42] Maynard Smith wrote that ‘The main task of any theory of evolution is to explain adaptive complexity, i.e. to explain the same set of facts which Paley used as evidence of a Creator’ (‘The status of neo-Darwinism’, in: C. H. Waddington [ed.], Towards a theoretical biology, [Edinburgh: Edinburgh University Press], cited in: Dawkins, ‘Universal Darwinism’, p.404).

Archicebus achilles, the Oldest Known Primate

One day, some 65 million years ago—at least, so it is thought to have happened—a meteorite, some 10km in diameter, smashed into the earth’s surface, throwing up an enormous dust cloud which darkened the skies, occluding the sun’s irradiance and lowering global temperatures. Verdancy declined as plants and other photosynthetic organisms were unable to photosynthesise. The hypothesis of a meteorite impact (Figure 1), proposed by father-and-son team Walter and Luis Alvarez in 1980 (with Frank Asaro and Helen Michel)[1], is widely thought to have been the cause of the Cretaceous-Paleogene (K-Pg) mass extinction (Tertiary is the informal name also used to refer to the period known as the Paleogene) in which nearly all marine plankton, ten families of marine invertebrates, and the illustrious dinosaurs, which had dominated the earth for the last one-hundred million years, were extirpated, and is considered the best candidate explanation for the layer of iridium–an extra-terrestrial element–found in rock strata across the globe, the age of which is precisely coincident with the K-Pg extinction. The Chicxulub crater which lies along the Yucatan peninsula in Mexico, measuring around 180km in diameter, is thought to be the impact crater caused by the meteorite responsible for the K-Pg extinction.

The sudden departure of the dinosaurs permitted our mammalian forebears—small, shrew-like creatures—to tentatively emerge from their burrows to which they had been largely confined throughout the 100-million-year reign of the dinosaurs lest they became a Tyrannosaurus’ lunch. With an abundance of ecological niches left vacant in the wake of the tide of extinction, the mammalian lineage underwent a profuse diversification, our forebears inheriting an earth left far more hospitable by the abrupt and unwitting departure of their unfortunate reptilian relatives.

Figure 1 The Chicxulub crater

This, of course, leads one to ask the counterfactual ‘What if…?’ prompted by any salient historical event. Imagine: no meteor; no extinction; no mammalian diversification; no primates; no great apes; no Homo sapiens asking ‘What if…?’. Stephen Jay Gould, waxing one of his favourite themes, the contingency of history, remarked that ‘In an entirely literal sense, we owe our existence as large and reasoning mammals to our lucky stars.’[2] Whilst I don’t believe that we are so indebted to our lucky stars,[3] the extinction of the dinosaurs at the end of the Cretaceous presented the mammalian lineage with a remarkable opportunity.

I offered the above as a slight preamble to the recent discovery of the oldest member of one of the lineages which evolved in the course of the great mammalian diversification which is of fairly personal interest due to its being belonging to our own order, the primates. Whilst I realise that the news is not particularly fresh, I had hoped to write a short piece on the discovery, given that it is so long since I last posted anything, and with having been rather busy, I have only just now been able to get down and finish it off.

Until just over a week ago the oldest primate remains had been dated around 48 million years old. However, the exquisitely preserved fossilised remains of a lemur-like primate (Figure 2) exculpated from a shale bed in eastern in China in 2002 is thought to be around 7 million years older, date around 54.8-55.8 million years, a discovery which promises to throw fascinating light on primate evolution.[4]

Figure 2 The fossilised remains of A. achilles

The specimen has been dubbed Archicebus achilles, the genus name roughly translating as ‘original long-tailed monkey’. The computer-generated image of the A. achilles (Figure 3) shows a remarkably endearing little fellow adapted for life in an arboreal habitat, its long hind-limbs, grasping feet (Figure 4) and tail which measured at least twice the length of its body fitting it for life in the trees.

Figure 3 A computer-generated image of A. achilles resting on a tree branch, about to chomp the head off an insect

Figure 4 The left (a and b) and right (c and d) foot regions of A. achilles

A. achilles, which resides at the base of the tarsier lineage (Figure 5), exhibits a mosaic of characteristics belonging to both the tarsier and arthropoid groups. The skull, teeth and limb bones of A. achilles resemble those of tarsiers, whilst its heel and foot bones (to which its species name alludes) resemble those of arthropoids, the primate group from which we evolved. The creature’s sharpened premolars suggest that it subsisted on an insectivorous diet and it is thought, from the eye sockets, that it was probably active during the day.

A. achilles was not one of our ancestors, as it does not belong to our lineage—not that we would be able to tell if it were an ancestor even if it did[5]–although it is thought those primates which were our ancestors probably would have looked something very like it.

Discoveries such as these are incredibly exciting—and, as the flurries of media frenzy which they elicit attest, not just for those within the scientific community. It is astonishing that the tree of life should have sprouted a branch capable of understanding, however partially, its growth and form. It is an extraordinary thing to look at the fossiliferous remains of A. achilles and to think of it scampering from branch to branch all those millions of years ago, and to seek to pinpoint whereabouts upon which branch of life’s great tree it resides. To discover the remains of one species among the billions which have populated this earth throughout the deep swathes of geological time and to discover new things about the process by which they came about is very special.

And what an adorable fellow he looks!

[1] Luis W. Alvarez, Walter Alvarez, Frank Asaro and Helen Michel, ‘Extraterrestrial cause for the Cretaceous-Tertiary extinction’, Science, 208 (4448): 1095-1108, (1980).

[2] Stephen Jay Gould, Wonderful life: the Burgess Shale and the nature of history, (London: Hutchinson, 1990), p.318.

[3] See Simon Conway Morris’ Life’s solution: inevitable humans in a lonely universe (Cambridge: Cambridge University Press, 2003) for a compelling counter to Gould’s thesis of contingency, leading one to reappraise Gould’s asseveration that ‘Homo sapiens is an entity, not a tendency’ ([see above note for reference], p.320). Conway Morris argues that, given the conditions which obtain on earth and the nature of Darwinian evolution, that whilst Homo sapiens is, of course, an entity, as the product of a unique historical process, that something like Homo sapiens–something self-conscious, rational, intelligent–is an inevitability. Whilst Conway Morris’ arguments are not uncontroversial, they should not be ignored.

[4] See Sid Perkins, ‘The oldest primate skeleton unveiled’, Nature, 5 June 2013, doi:10.1038/nature.2013.13142, available at: http://www.nature.com/news/oldest-primate-skeleton-unveiled-1.13142.

[5] This point is well made by Henry Gee (who, incidentally, is one of Nature‘s senior editors) in his book Deep time: cladistics, the revolution in evolution (London: Fourth Estate, 1999).

The Happening of Evolution

Is evolution a fact? In the previous post, we noted that a ‘fact’ in science is not apodictic, but always provisional—it may always be confounded by a new discovery.  Following Ruse’s proposition, we considered the three-fold division of evolution into (1) its happening, (2) its paths and (3) its mechanism. If each of these (admittedly interdependent to differing extents) elements can be satisfactorily established, then, yes, we may declare evolution a fact beyond reasonable doubt.

Darwin’s Theory

Darwin presented his theory of evolution as ‘one long argument,’[1] not in a dense, unwieldy tome solely within the purview of the cognoscenti, but in a work of popular science, which could be followed by the lay reader. In this work, the Origin of Species, Darwin sought to marshal evidence from a variety of disciplines in order to establish a Whewellian consilience of inductions: his theory of evolution explicating the evidence; the evidence, in turn, pointing to his theory.

The idea [of a consilience] is that somehow, if a hypothesis is true—tells us about the real world—then various facts or other claims follow from it, and will keep doing so. And there is a kind of feedback process here. As the hypothesis leads to new information, so its derivations themselves confer a kind of probability upon the hypothesis.[2]

It would help to briefly consider what Darwin’s theory actually was. According to Darwin, species were not immutable, but were the product of a gradual process of evolution, the primal (though not sole) cause of which was natural selection. Today, his theory is commonly referred to as ‘evolution by natural selection’; Darwin referred to his theory as ‘descent with modification’. Philosopher of biology Elliott Sober has argued that these characterisations do not accurately convey the essence of Darwin’s theory suggesting that Darwin’s theory be referred to as ‘common ancestry plus natural selection.’[3] This characterisation acknowledges the relative indepdendence of each of the two ideas, an independence which can be appreciated historically, for whilst Darwin did much to convince the scientific community of the first idea, he failed to convince even some of his closest ‘disciples’ of the second.[4] Nevertheless, the thesis of common ancestry is absolutely integral to Darwin’s theory. If common ancestry can be demonstrated, then species cannot be immutable and one is forced to propose a mechanism to account for the process.

Sober and Orzack note that ‘the best evidence of common ancestry comes from neutral or even deleterious features.’[5] As Gould frankly puts it, ‘ideal design is a lousy argument for evolution.’[6] According to an evolutionary hypothesis, adaptation is the result of natural selection. But if adaptation is perfect, then an evolutionary hypothesis becomes less likely, as perfect adaptation is more suggestive of intelligent design. If, on the other hand, adaptation is not perfect, or if there are non-adaptive or maladaptive traits, then a hypothesis of intelligent design becomes less likely and an evolutionary hypothesis more likely. As Stephen Jay Gould writes, ‘you cannot demonstrate evolution with perfection because perfection need not have a history.’[7] However, ‘if organisms have a history, then ancestral stages should leave remnants behind.’[8] History is revealed by ‘the useless, the odd, the peculiar, [and] the incongruous’.[9] Natural selection effaces the marks of history. This is what makes evolutionary convergence (the evolution of similar features in independent lineages) such a nuisance for phylogeneticists. Is the feature shared by two groups homologous (due to common ancestry), in which case a close phylogenetic relationship is inferred? or is it due to convergence, in which case it would be a mistake to infer a close phylogenetic relationship?[10] Thus, ‘The more a trait’s distribution can be explained solely on the basis of natural selection, the less evidence the trait will provide for shared ancestry.’[11] One must look, then, to those non-adaptive or maladaptive traits in order to prove the happening of evolution.


Homology provides perhaps the most striking confirmation of evolution. Darwin was convinced that the exquisite adaptations which pervade the living world were the result of natural selection ‘daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good’,[12] yet natural selection can only work with what is to hand. An intelligent designer could presumably fashion a novel structure of whatever materials required, but such a luxury is denied to selection. Selection can only modify existing structures, making do with whatever is to hand, as it were: ‘the parts may change to almost any extent in form and size, and yet they always remain connected together in the same order.’[13] Homologies are testament to common ancestry. Unlike convergences, ‘Entities are homologous if, in principle, they can be traced back to a single genealogical precursor.’[14]

Several homologous vertebrate forelimbs

Looking within our own subphylum, the vertebrate forelimb presents a striking example of homology. If you take a look at the diagram above, you can see that the limbs of humans, dogs, whales and birds are all variations on a common theme. One can see the humerus, the radius and ulna of the lower arm, as well as the digits (reduced to three in birds). Whilst the limb in each species is adapted for a particular function, it is apparent that the isomorphisms are due to the inheritance of the structure from an ancestor common to all four species. Homologies such as these only make sense in the light of evolution, and that is what makes them such good pieces of evidence. As Darwin wrote, uttering a common refrain throughout the Origin, ‘On the ordinary view of the independent creation of each being, we can only say that so it is; – that it has so pleased the Creator to construct each animal and plant.’[15]


Just as only ‘descent with modification’ can adequately explain homology, so can only evolution adequately explain the other classes of facts Darwin considered. To take a second example used by Darwin we look to biogeography; a subject to which he devoted two chapters in the Origin. This area provided perhaps the most cogent proof of evolution; both Alfred Russel Wallace and Joseph Hooker came to accept evolution on account of the geographical distribution of species. Biogeography was also cenral in Darwin’s conversion to and discovery of evolution. Richardson writes that ‘Ultimately, biogeography offered the only sufficiently elaborated body of knowledge on the relationship of species to their environment, and to changes in that environment, that could constitute a valid test case for Darwin’s developing theoretical speculations on transmutation and his search for an efficient cause of change.’[16] Why should it be that, despite highly similar environmental conditions prevailing in regions of distant continents the species that one finds there invariably bear close resemblance to the species of that area and not of the distant area?

If we look to the islands off the American shore, however much they may differ in geological structure, the inhabitants, though they may be all peculiar species, are essentially American…We see in these facts some deep organic bond, prevailing throughout space and time, over the same areas of land and water, and independent of their physical conditions.[17]

What could account for the similarity between neighbouring species if the environmental conditions appeared to be irrelevant? If one Australian species would have been just as well adapted to the environment of an American species, why should the two species be so dissimilar yet bear such peculiar affinities to the species of their homeland? ‘This bond, on my theory,’ wrote Darwin, ‘is simply inheritance, that cause which alone, as far as we positively know, produces organisms quite like, or, as we see in the case of varieties nearly like each other.’[18] It is migration that is responsible for the similarities between mainland and offshore species, and it is restrictions to migration which are responsible for the differences between species inhabiting identical environments on opposite sides of the globe. At the close of the second chapter on biogeography, Darwin writes, ‘I think all the grand leading facts of geographical distribution are explicable on the theory of migration…, together with subsequent modification and the multiplication of new forms.’[19]

Geographical distribution of Galápagos tortoises


In a letter to Joseph Hooker, Darwin referred to the section on embryology as his ‘pet bit’[20] of the Origin. Darwin had written that ‘certain organs in the individual, which when mature become widely different and serve for different purposes, are in the embryo exactly alike.’[21]If one looks at, say, the early embryo of a human and the early embryo of a fish the two embryos are remarkably similar; even though the two go on to develop into very different organisms. And the early stages of the human embryo resemble the adult forms of ancestral forms. Darwin goes on to write that ‘The embryos, also, of distinct animals within the same class are often strikingly similar: a better proof of this cannot be given, than a circumstance mentioned by Agassiz, namely, that having forgotten to ticket the embryo of some vertebrate animal, he cannot now tell whether it be that of a mammal, bird, or reptile.’[22] As evolution proceeds, newer developmental instructions are layered on top of more ancient instructions, forming a kind of developmental palimpsest.

We cannot, for instance, suppose that in the embryos of the vertebrata the peculiar loop-like course of the arteries near the branchial slits are related to similar conditions,—in the young mammal which is nourished in the womb of its mother, in the egg of the bird which is hatched in a nest, and in the spawn of a frog under water. We have no more reason to believe in such a relation, than we have to believe that the same bones in the hand of a man, wing of a bat, and fin of a porpoise, are related to similar conditions of life… In two groups of animal, however much they may at present differ from each other in structure and habits, if they pass through the same or similar embryonic stages, we may feel assured that they have both descended from the same or nearly similar parents, and are therefore in that degree closely related. Thus, community in embryonic structure reveals community of descent.[23]

Molecular Genetics

Homology, biogeography and embryology provided three lines of evidence which Darwin wove into his consilience. A fourth line of evidence which was not available for Darwin but which provides eloquent confirmation of the happening of evolution comes from molecular biology. It is a striking fact that all organisms share the same genetic material. Not only do all organisms share the same genetic material, they also share the same genetic code. This is an instance of a ‘universal homology’.[24] A triplet code is written in the four-letter nucleotide alphabet of DNA codes for an amino acid (the constituent building block of a protein or polypeptide). For example, the triplet code GGC (guanine·guanine·cytosine) codes for the amino acid glycine. With a triplet code composed of four letters, there are 43 possible triplets to code for only 20 amino acids (as well as punctuation marks), so that there is a great deal of redundancy in the code, so that, for example, GGG (guanine·guanine·guanine) also codes for glycine. As Sober notes,

As long as there are multiple codes that each would work, a shared code is evidence for common ancestry. And the more such codes there are, the stronger the evidence that the near-universality of the code provides for common ancestry. This point holds even if the shared code we observe in the life around us turns out to be optimal.[25]

It is not inconceivable that different groups of organisms should have different codes, and for this reason the universality of the code (with its minor variants) testifies to the happening of evolution. The most satsisfying explanation for the universality of the code is descent with modification.


The pieces of evidence presented here have provided confirmation of the first element of evolution: its happening. Only if descent with modification—that is, evolution—has occurred can we satisfactorily account for the facts before us. The theory of evolution wields extraordinary explanatory power, accounting for a plethora of otherwise disparate facts. The happening of evolution can be known without knowing the causal mechanisms responsible. In the next post, I shall consider the second element of the theory of evolution: its paths.

[1] C. R. Darwin, On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life, (London: John Murray, 1859), p.459.

[2] M. Ruse, Darwinism and its discontents, (Cambridge: Cambridge University Press, 2008), p.38.

[3] E. Sober, ‘Did Darwin write the Origin backwards?’, Proceedings of the National Academy of Sciences, 106 (1): 10048-10055, (2009), p.10050.

[4] See P. J. Bowler, The non-Darwinian revolution: reinterpreting a historical myth, (Baltimore, ML: The Johns Hopkins University Press, 1988).

[5] E. Sober and S. Orzack, ‘Common ancestry and natural selection’, British Journal for the Philosophy of Science, 54: 423-437, (2003), p.427.

[6] S. J. Gould, ‘The panda’s thumb’, in The panda’s thumb, chap.1, (New York: W. W. Norton & Co., 1980), p.20.

[7] S. J. Gould, ‘Senseless signs of history’, in The panda’s thumb, chap.2, p.28.

[8] Ibid.

[9] Ibid.

[10] On evolutionary convergence, see S. Conway Morris, Life’s solution: inevitable humans in a lonely universe, (Cambridge: Cambridge University Press, 2003); also see http://mapoflife.org/index/.

[11] Sober and Orzack, ‘Common ancestry and natural selection’, p.428.

[12] Darwin, On the origin of species, p.84.

[13] ibid., p.434.

[14] M. Ghiselin, The triumph of the Darwinian method, (Mineola, NY: Dover Publications, Inc., 2006), p.110.

[15] Darwin, On the origin of species, p.435.

[16] R. A. Richardson, ‘Biogeography and the genesis of Darwin’s ideas on transmutation’, Journal of the History of Biology, 14 (1): 1-41, (1981), p.6-7.

[17] Darwin, On the origin of species, p.350.

[18] Ibid.

[19] Ibid., p.408.

[20] C. R. Darwin, Letter to Joseph Dalton Hooker, 14 December 1859, http://www.darwinproject.ac.uk/entry-2583.

[21] Darwin, On the origin of species, p.439.

[22] Ibid., p.439-440.

[23] Ibid., p.449.

[24] M. Ridley, The problems of evolution, (Oxford: Oxford University Press, 1985), p.10.

[25] Sober, ‘Did Darwin write the Origin backwards?’, p.10053.