This post is the first in a series on faith, religion and Darwinian natural selection. This series does not concern a form of social Darwinism founded on such odious principles as the “survival of the fittest” – which, incidentally, was a phrase coined not by Darwin but by Herbert Spencer, a biologist and philosopher who attempted to establish Darwin’s scientific framework in the social realm – but, rather, is a consideration, and in parts defence, of Charles Darwin’s grand idea; his revolutionary theory of evolution by natural selection, which is now recognised as the primary evolutionary “programme,” as it is now understood in the neo-Darwinian synthesis (the incorporation of Mendelian genetics in the Darwinian framework – non-random selection of random genetic mutation (formulated by such acclaimed scientists as Theodosius Dobzhansky and Ernst Mayr)).
In this post I aim to give a brief overview of the history of evolutionary thought and to detail some of the discoveries which led to the synthesis of neo-Darwinism. The subsequent posts shall then examine objections to the theory where I shall attempt a defence of Darwinism and consideration of faith, both scientific and religious, in relation to Darwinism, before concluding with a consideration of the scientific endeavour itself.
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1. Charles Darwin…
Charles Darwin (1809-1882)
Charles Darwin’s (1809-1882) On the Origin of Species was published on Thursday 24th November 1859, priced at fifteen shillings, and revolutionized biology. Whilst a number of scientists had whiffed the aroma of the idea, had their appetites whet by a suggestion of the principle, or had even begun to see the idea as certainly possible – the equivalent of tasting the wine, or eating the first morsel of the dish – Darwin’s book served up the principle of evolution by natural selection on a platter, accompanied by a large dish of empirical evidence, which is what was necessary for the theory to leave the realms of theory without evidence to a higher steppe of empirical reasoning.
HMS Beagle set sail from Plymouth on 27th December 1831, amongst the crew a geologist and naturalist who had amassed a reputation as a collector of fossils. This man’s name was Charles Darwin. The Beagle sailed along the coast of South America, and here Darwin analysed the tortoises of the Galápagos Islands, which were to feature in his discovery. Darwin was able to collect various fossil samples and it was the research undertaken on this journey that formed the basis for the theory and the data which support it. The voyage of HMS Beagle had been intended as a two-year excursion but came to an end after five years.
Darwin developed his the theory of evolution by natural selection in an admirable, scientifically proper manner, refraining from publishing his work impetuously, instead toiling for the truth and foraging through the data which he had acquired, letting the evidence lead him where it may. Twenty-eight years elapsed between 1831 (the voyage of the Beagle) and 1859 (the publication of On the Origin of Species) and when Darwin’s most famous work was published he had prepared thoroughly, with the matters which may have been subject to questioning ready with evidential responses.* However, whilst Darwin’s work was exquisite, it was by no means conclusive. For instance, Darwin knew that characteristics were inherited but he knew not by what means. He proposed a theoretical “gemmule” as the mode of inheritance. Darwin did not develop an unblemished, theoretical masterpiece of biological science, but he laid the foundations for a productive foray into the field of evolutionary biology and, primarily, showed us by what mechanism: natural selection.
and Friends
Gregor Mendel
Gregor Mendel (1822-1884)
Gregor Mendel (1822-1884) a Augustinian monk and scientist earned the title “The Father of Modern Genetics” and rightly so. Mendel, whilst at St. Thomas’ Abbey, experimented with pea plants, breeding them and tirelessly analysing the offspring, recording all of the results with an indefatigable impeccability. One of the most important areas of the discovery was the colour of the pea plants.
Mendel would take yellow peas and would breed them and record the colour of the offspring. Mendel succeeded in refuting the conventional thought on inheritance at the time of Darwin which claimed that characteristics from the parents were blended together to produce the child’s personal traits in a kind of “inheritance smoothie.” (This view was problematic for Darwin’s theory, as his idea stated that successful traits would be maintained throughout the generations if they aided survival, whereas the notion of blending would incur the dilution and subsequent loss of a trait as it was blended throughout the generations.) Mendel’s experiments with pea plants showed that the offspring from a yellow pea plant would be yellow and green at a ratio of 3:1. According to contemporary conventional thought the offspring should have all been a yellowy-green. But instead Mendel’s pea plants exhibited this discrete colour pattern. Mendel realised that traits were not blended in a mixture, but that they were inherited in discrete hereditary quanta (what we now know to be genes).
Punnett square displaying Mendels results
Mendel’s experiments laid the foundations for modern genetics. Mendel was able to infer that there must be “dominant” and “recessive” particulate units of inheritance (what we now know as “alleles”). The unit specifying a yellow plant was the “dominant” trait (A in the above diagram) and the unit specifying for a green plant was a “recessive” trait (a in the above diagram). In the Punnett Square above you have a 2×2 grid with A and a in separate squares both on the x and y rows. Each trait (A and a) is worth ½, so you need two “half-units” to make the full unit. However, because the A trait is dominant you only need one “half-unit” of A and the plant will be yellow. The only opportunity a recessive (a) has to determine the colour of the plant is if A is totally absent. So, when we multiply out the units:
AA = dominant
Aa = dominant
Aa = dominant
aa = recessive
Mendel’s discovery of particulate hereditary units formed the basis for modern genetics and the neo-Darwinian synthesis is founded strongly on the principles of genetics. Another defining characteristic of neo-Darwinism is its emphasis on random genetic mutation which can then be acted on by non-random natural selection. The Mendelian perspective also shows us how singular traits can be maintained throughout a family lineage, as a “successful” gene (i.e. a gene that aided survival and reproduction) being a particulate unit would not be blended and “diluted” in the genealogy of blendings, but would, rather, survive intact, kept in there by the guiding hand of selection.
Thomas Hunt Morgan
Thomas Hunt Morgan (1866-1945)
Thomas Hunt Morgan (1866-1945) was an embryologist who furthered understanding of chromosomes and their influence on the organism’s manifestation (what would come to be known as the genotype on the phenotype) while studying the fruit fly, Drosophila melanogaster. The chromosomes of the fruit fly are fairly large, as chromosomes go, and Morgan was able to observe these. He then studied the fruit fly and found that he could group its characteristics into four different types. The significance of the number four? The fruit fly has four chromosomes. But the developments which Morgan was making did not halt here. He found that there was one group of characteristics which was slightly smaller than the rest, and so he found that one of the chromosomes of the fruit fly was smaller than the rest! What was beginning to happen was that from Darwin’s vision of natural selection, Mendel had discovered particulate hereditary quanta and had recognised the principles of inheritance. Hunt Morgan and similar early research to this was beginning to pin-point the location of these units (the chromosomes) bringing what had been empirically proven in theory into actual biological study. The neo-Darwinian synthesis was ever-emerging.1
Watson and Crick
Perhaps the greatest scientific discovery in the biological field since Darwin, the discovery of the structure of DNA – the genetic code – by James D. Watson (b. 1928) and Francis Crick (1916-2004) unlocked the secret of life.
James Watson (left) and Francis Crick (right)
In 1943, the renowned physicist Erwin Schrödinger delivered a series of lectures at Trinity College, Dublin on the title “What is life?” and said, “It is these chromosomes… that contain in some kind of code-script the entire pattern of the individual’s future development and of its functioning in the mature state.”2 It was becoming clear that the chromosomes somehow contained this “code-script,” though quite how it was contained and what the actual “code-script” was remained a mystery. DNA “had first been isolated, from the pus-soaked bandages of wounded soldiers, in the German town of Tubingen in 1869 by a Swiss doctor named Friedrich Mieschler [who] guessed that DNA might be the key to heredity… [However] DNA had few fans [and] was known to be a comparatively monotonous substance.”3
Watson and Crick were an unlikely pair: Watson promising and precocious, nineteen years of age and already with a bachelor’s degree; Crick the opposite: he was thirty-five years of age (a difference of sixteen years between the two of them) and without a PhD. However, they both shared the enthused belief that the secret of life (nothing too mundane) lay with DNA and so began a series of examinations and experiments which led to the discovery of the exquisitely elegant double helix – the emblem of life. On 28 February 1953, Francis Crick ran into The Eagle pub and exclaimed, “We’ve found the secret of life!” Then, on 25th April 1953, Watson and Crick published their revolutionary paper entitled Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid in the scientific journal Nature changing biology and the sub-discipline of biological evolution forever.
The DNA Revolution
However, whilst Watson and Crick had discovered the structure of DNA, cracking the code proved the next obstacle and more problematic. Crick was responsible for much of the theorizing behind the genetic code. The letters of the “code-script” were known (A, C, G and T (standing for the nucleotide bases adenine, cytosine, guanine and thymine)) and it was certain that this base alphabet would code for the twenty-letter code of the amino acids which are the building blocks of proteins. But just how it actually did this was the mystery.
However, through the 1960s many discoveries were made and continued to be made with greater frequency throughout the 1990s and into the 2000s, culminating in the grand achievements of the Human Genome Project which was launched in 1990 and completed in 2003, whose objectives were to:
- “identify all the approximately 20,000-25,000 genes in human DNA,
- determine the sequences of the 3 billion chemical base pairs that make up human DNA,
- store this information in databases,
- improve tools for data analysis,
- transfer related technologies to the private sector, and
- address the ethical, legal, and social issues (ELSI) that may arise from the project.”4
DNA is found in the chromosomes of an organism, which are in turn founded in the cell nucleus of an organism (see diagram below). In the case of humans, chromosomes invariably number 46, although the number varies for other kinds of organisms, although within one kind the number will remain the same. Humans inherit 23 chromosomes from the mother and 23 chromosomes from the father (technically, humans inherit 22 complementary pairs of chromosomes from each parent and then an X or Y chromosome from each parent (XX making the child female; XY making the child male) when the sex cells (“gametes”) – the egg in the case of the mother and the sperm in the case of the father – fuse in sexual reproduction to form a complete cell with 46 chromosomes (a zygote). In the chromosomes DNA is packaged in chromatin. The purpose of DNA is (predominantly) to encode the recipes for the proteins to be manufactured, in the four-letter alphabet of A, C, G and T.
Packaging of the chromosome
The illustrious structure of DNA consists of two spiralling swirls (helices) of a sugar phosphate (see diagram, below). And extending along the spiralling frames are a series of “base-pairs.” The nucleotides adenine, cytosine, guanine and thymine form something like varying rungs on the ladder of the sugar phosphate. Except, rather than one base forming one rung, two bases form one rung, as a pair. And the bases in the pairs specify one another diametrically, so an A “half-rung” specifies a T half-rung (and vice versa) and a C half-rung specifies a G half-rung. These base-pairs can then specify certain functions.
A strand of DNA
In DNA replication, the two diametrically complementary strands separate (see diagram below) and then polymerases are responsible for the formation of complementary half-rungs along the “half-ladders,” so that one strand of DNA begets two daughter strands and therefore the self-perpetuation of the genetic material encoding an organism by replication. It is DNA replication which makes evolution possible and this is one of the Mendelian revolutions which led to the formulation of the neo-Darwinian synthesis – non-random selection upon random genetic mutation. For when DNA replicates it does so imperfectly, i.e. mutations occur. This may be the alteration of an A to a G (a “point mutation”) which may or may not alter the protein manufactured. (A “triplet codon” (a three-letter base sequence) codes for one amino acid in a protein, but more than one codon may code for a certain amino acid so a single point mutation may not alter the amino acid and therefore the protein specified.) These point mutations – the mutations of base letters – are like misspellings.
DNA replication
DNA replication is not too imperfect however, and almost always makes faithful replications, for if it were too errant it would only be harmful to the organisms, as there would be no stability. Genetic variation can be beneficial and it can be harmful, but it is largely neutral. However, “when genetic variation does make a difference to the organism, for good or ill, natural selection begins to operate and the organism will tend to leave, over many generations, greater or fewer numbers of offspring, a process known as ‘reproductive success.’”5
Other kinds of “mutations” include:
- “Deletions: A portion of the chromosome is missing or deleted.
- Duplications: A portion of the chromosome is duplicated, resulting in extra genetic material.
- Translocations: When a portion of one chromosome is transferred to another chromosome. There are two main types of translocations. In a reciprocal translocation, segments from two different chromosomes have been exchanged. In a Robertsonian translocation, an entire chromosome has attached to another at the centromere.
- Inversions: A portion of the chromosome has broken off, turned upside down and reattached, therefore the genetic material is inverted.
- Rings: A portion of a chromosome has broken off and formed a circle or ring. This can happen with or without loss of genetic material.”6
All of which can alter the structure and function of an organism, for “good or ill.”
Conclusion
In this post I aim to have detailed some of the discoverers and their discoveries relevant to the formulation of neo-Darwinism – Darwinian selection in the light of modern Mendelian genetics. Darwin did not know of Mendel’s work, even though the two were contemporaries. However, sadly for Mendel, the importance of his experiments with pea plants was not realised by those who knew him and the sequestered monastery was hardly the thoroughfare of scientific discovery. It has only been in the last century that Mendel has been recognised for his work and retrieved from the depths of obscurity and hailed the Father of Modern Genetics. Mendel showed us that the units of heredity are particulate discrete quanta and showed us a new vision of heredity altogether.
Darwin laid the foundations for the modern era of evolutionary biology. Heaps of empirical proof supported his hypothesis that natural selection is not the sole but the primary means of evolution. He demonstrated how, with an incredibly elegant and stunningly simple theoretical framework, we could understand not (contrarily) the origin but the creation, the generation of species. The unfolding of life was revealed with the publication of a book on Thursday 24th November 1859 priced at fifteen shillings. A book worth infinitely more in terms of its brilliance and vision.
James D. Watson and Francis Crick, two brilliant – yet unlikely – scientists unlocked the structure of DNA – the secret of life. The discovery of the structure of this most amazing molecule unveiled Mendel’s particulate units, and the subsequent discoveries of the DNA revolution have led those such as Dobzhansky and Mayr to an overwhelming synthesis, incorporating the findings of a Victorian English naturalist, an Augustinian Monk, and a whole host of some of the most brilliant minds in science – the neo-Darwinian understanding of “evolution by non-random selection – the only game in town, the greatest show on earth.”7
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* This is according to the traditionalist view. The late Stephen Jay Gould, in the essay “Darwin’s Delay,”8 writes that the reason for the late publication of Darwin’s Origin was not simply the timely accumulation of data, or refinement of the theory (although, of course, this would have occurred in those twenty-eight years), for after his return from the Beagle‘s voyage he devoted eight years to the writing of four weighty tomes on barnacles! Darwin later wrote that he “doubt[ed] whether the work was worth the consumption of so much time.” Gould writes that “the negative effect of fear must have played at least as great a role as the positive need for additional documentation.”
But what was Darwin afraid of? Not, as is commonly thought, of revealing his belief in the heresy of evolution, as this was “a very common heresy during the nineteenth century,” but his fear of revealing his materialism. “No notion could be more upsetting to the deepest traditions of of Western thought than the statement that the mind – however complex and powerful – is simply a product of brain.”9 From Darwin’s notebooks it is evident that he was materialistically inclined, whilst his friend and co-discoverer of natural selection, Alfred Russel Wallace, could not bring himself to admit materialism, and insisted that the human mind was divinely contrived. It was not simply collecting data that caused Darwin to delay, but the intolerance which would be shown him were he to admit such a philosophical view.
(We can wonder whether the Origin would have been published if Darwin had not wished to publish his findings before Wallace beat him to it. (Darwin had intended to to lay out his theory in a collection of detailed volumes, rather than in the few-hundred pages of the Origin.))
References
1 McGrath, A. (2005). Dawkins’ God: genes, memes, and the meaning of life. (Blackwell: Oxford).
2 Schrödinger, E. (1967). What is life? mind and matter. (Cambridge University Press: Cambridge). quoted in Ridley, M. (1999). Genome: the autobiography of a species in 23 chapters. (Fourth Estate Limited: London). p.14
3 ibid. p.48.
4 Human Genome Management Information System. (2008). “What is the Human Genome Project”. [online] http://www.ornl.gov/sci/techresources/Human_Genome/project/about.shtml [Accessed 24th April 2011]
5 Alexander, D. (2008). Creation or evolution: do we have to choose? (Monarch books: Oxford).
6 National Human Genome Research Institute. (2010). “Chromosome abnormalities”. [online] http://www.genome.gov/11508982 [Accessed 25th April 2010]
7 Dawkins, R. (2009). The greatest show on earth: the evidence for evolution. (London: Bantam Press). p.426.
8 Gould, S. J. (1977). “Darwin’s Delay”, in Ever since Darwin: reflections in natural history. (New York: Norton).
9 ibid. p.23.
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Francis Smallwood, 2011
