February 12, the anniversary of the birth of Charles Darwin, has been declared International Darwin Day (celebrated for the first time this year). Darwin’s The Origin of Species dealt a death-blow to the myth of Creation which has been, and still is, the cornerstone of the Abrahamic religions. Ever since religionists have sought to discredit Darwin. In this modest tribute to Darwin it is shown that after a century and half Darwin remains vindicated.



Darwin Vindicated

by Victor Gunasekara


The conflict between the human intellect and Supernatural Religion is best typified by the examples of Galileo and Darwin. Other men and women of science and reason too have fallen foul of theistic religion, but these two great thinkers are noted for the scope of the theories with which they are associated, and the hatred directed at them by the religious establishment.

       Of the two Galileo suffered the more. He was hauled before the Inquisition and was only spared some of its barbarous punishments by agreeing to “recant” his views. Darwin lived in more enlightened times when many freedoms had been won thanks to the enlightenment and the work of humanists. Yet he too has suffered from the venom and vituperation of religionists, perhaps to a greater extent. This is because his theory strikes at the very heart of the their religion, viz that the entire world, and all living things within it, were created by God. Theists may be able to live with the idea that the earth is not the centre of the Universe but they cannot live with a notion of God that deprives him of his principal attribute.


The Significance of Darwin

       Darwin was one of the few great revolutionaries in scientific thinking of all time. His ideas may not have been completely original, even in the area of evolution. His theories, like all scientific work, have been amended and enlarged by subsequent scientific work. His achievement was to have opened a new paradigm on that most intriguing of questions, viz. how species, including humans, came to be what they are. At the very least Darwin crystallised and consolidated an emerging stream of thought which would have led, even without him, to the triumph of evolution over creation. His real achievement was however much greater than this

       His credit is all the more because the area of his investigations was one which had been the preserve of religion for centuries and had developed powerful vested interests in its defence. [1] Yet Darwin was able to replace it with a new perspective not by attacking the old ideas directly but by building an irrefutable case for the contrary. With his scientific method he had no need to resort to rhetoric as has been the case with those who had previously contested religious claims.

       There are many aspects to consider in evaluating the ideas of Darwin in this first International Celebration of Darwin. First and foremost is his contribution to the question of the origin of species, which, following Herschel, he has called the “mystery of mysteries” (Origin, p.65). Even if he did not clear up the whole of this great mystery he did leave it less of a mystery.

       Today there is a great industry promoting what is called “Creation Science” (which will be noticed later).. This movement is not without public support and in some educational systems both evolution and “Creationism” (as its proponents like to call it) are treated as alternative explanations of the phenomenon of how existing species came into being. This of course does not indicate any failure on the part of Darwin but is a testimony to the power of religion even in this “enlightened” age.

       While Darwin placed his ideas firmly in the physical and biological world there subsequently developed a movement to extend them to the non-physical arena. This has been termed “Social Darwinism”, an extension of Darwin’s theory largely associated with one of Darwin’s early followers Herbert Spencer (1820-1903). It did not find much favour with Darwin himself, and cannot be attributed to him directly. We will not be considering it here.


Some Biographical Facts

       Charles Darwin was born in 1809 in Shrewsbury, Shropshire. He came from a distinguished family, his grandfather Erasmus Darwin was an evolutionary naturalist who wrote a work entitled Zoönomia (1794). Charles’ father, a wealthy physician, send him first to Edinburgh to study medicine and then to Cambridge to study theology. Charles did not distinguish himself in either of these endeavours. However at Cambridge he befriended Adam Sedgewick, professor of Geology and John Henslow, professor of Botany who kindled an interest in naturalism in the young Darwin.

       Darwin found his true vocation when in 1831, shortly after graduating from Cambridge, he was appointed as a naturalist to accompany a scientific expedition on board the Beagle. It was on this voyage that he amassed a wealth of details of the fauna and flora of the places visited which included South America, the Pacific and Australasia. It was also during this trip that the theory he is best associated with germinated, particularly after his study of the fauna in the Galapagos Islands, off the west coast of South America..

       He returned to England in 1837, married Emma Wedgewood in 1839, and settled down in Down House at Downe in Kent in 1842 where he was to spend the rest of his days. He devoted his time to writing, scientific work and an extensive correspondence with the leading naturalists of his day. Most of his publications during his lifetime related to tracts in the areas of naturalism, geology, and biology.

       The theory of natural selection was conceived quite early after his return from the Beagle expedition. As early as 1844 he wrote it down in an unpublished and untitled essay. [2] The two works for which Darwin is best known, and will be our main concern here, are The Origin of Species (1859) and The Descent of Man (1871).

       In 1875 he wrote a short autobiography, which was only published posthumously. Darwin died in 1882, his last years marked by ill health from Chagas Disease he had contracted in South America.

 

Evolution as Fact and as Theory

       At the very start we have to distinguish between the fact of evolution and the theory of evolution. Failure to understand this distinction is the root cause of many attacks on Darwin. Darwin made contributions to both these aspects of what is referred to as “evolutionism”.

       The fact of evolution is the view that species did not come into being fully formed in the way we encounter them today, but have gone through a number of gradual transformations. Since the rate of progression is slow compared to the life of a single individual we do not see this process within the normal time-frame we are used to. But ever since the interpretation of the fossil record scientists have been able piece together this gradual transformation in the case of hundreds of different species. Moreover with the development of reliable methods of dating fossils we also have a time-frame into which we can fit the evolutionary process.

       The fact of the progressive mutation of species had been hypothesised at least a century before Darwin. Amongst those who had hinted at this possibility were Buffon, Diderot, St Hilaire and Lamarck in France, Linnaeus in Sweden, Goethe and Hackel in Germany and Erasmus Darwin in England. Charles Darwin himself acknowledged these in the historical introduction he added to his 1859 work. Darwin’s contribution in this area was to add a whole wealth of new information to show the empirical fact of the mutability of species. If before him the fact of evolution had been a good conjecture after Darwin it had become an irrefutable certainty. Even without a theory of evolution this would have been a seminal contribution.

       The theory of evolution on the other hand is a hypothesis of what drives the process of evolution. It is here that Darwin can claim originality. Previous to this the favoured explanation is what has been called the “inheritance of acquired characteristics”. According to this species would acquire certain characteristics, perhaps as a response to changes in the environment, or as human interventions, and these were passed into the offspring thus creating subtle changes in the species. Over long periods of time these gradual changes could transform the species and even lead to a new species. [3] But in the Origin of Species (1859) Darwin presented the new theory of natural selection.

       In his second major work The Descent of Man (1871) Darwin applied his theory to the evolution of humans. This was an even greater challenge to orthodox religion because the creation of Adam and Eve had been considered God’s supreme achievement. Now man came into being through a completely different route.


The Principle of Natural Selection

       The principle of natural selection as the engine of evolution, which Darwin had been working on since 1842, was also independently arrived at by another naturalist working in the East Indies. Alfred Russell Wallace wrote to Darwin in 1858 giving his views. Darwin arranged for Wallace’s paper to be read, together with one of his own on the same subject, at the Linnean Society in London in July 1858. This was the first time the theory was presented to the scientific world, and at the time did not create much interest. Darwin then, rather hurriedly, published a fuller version of his theory in 1859 as the Origin of Species. This immediately ignited a great controversy which has still not ceased.

       The Darwin-Wallace theory depends on two basic propositions:

(1) In any given species there are differences between individuals (e.g. in limb size or body colouration) and some of these are inheritable. (Origins, ch. 3)

(2) There is a struggle for survival [4] in any species and only those individuals with characteristics that suit the environment will survive and procreate offspring. (Origins, chs. 4-5)

As a result of these factors there is a natural process leading to the selection of those who are the fittest and their characteristics become typical for the species.

       The rest of Darwin’s 1859 work was devoted to discussing difficulties with the theory, and detailing a wealth of evidence to prove his theory.

       The theory of natural selection was immediately attacked by clerical figures like Bishop Wilberforce, but was also defended strongly by the scientists like Thomas Huxley (sometimes called Darwin’s bulldog).

       In the period after Darwin biological science developed the theory of genetics and in the middle of the twentieth century DNA was discovered leading to the complete mapping of the human genome. These developments did not contradict the principle of natural selection, but gave it support from areas which Darwin would not have suspected. This combination of the original Darwinian conjecture and the new developments in biological science has been called Neo-Darwinism. A recent writer has put the contemporary position as follows:

 

“By the 1950s a neo-Darwinian consensus tied genetics firmly to evolutionary change. Subsequent developments in molecular biology have greatly expanded the consensus. Once the sheer scale of genetic information becomes clear ... the near inevitability of inherited changes follow”. (Philip Whitfield, op. cit. , p. 16)


       Today neo-Darwinism is the key concept in a number of sciences such as zoology, botany, genetics, molecular biology, anthropology, palaeontology etc. The concept of evolution has thus become all pervasive.

       Neo-Darwinism is itself not without its critics. Scientific criticism has to be distinguished from the irrational criticism of religionists (which will be noted later) [5] . While we cannot go into the controversies which followed the publication of Darwin’s book [6] , nor the modern scientific critique of neo-Darwinism, some of the issues involved in the latter critique may be noted.

       One controversy relates to a difficulty in the first proposition of Darwin’s theory as to how differences emerge between individuals on which natural selection works. Darwin thought that this was a random process like genetic mutation in neo-Darwinism. It has been argued that such random changes are too slow to account for the emergence of what Darwin called “organs of extreme perfection and complication”, such as the eye. Darwin had noted this difficulty (Origins, p.217) but felt that given sufficient time and possibility of variation in eye structure it was not impossible for the eye to evolve through natural selection. A modern defence of Darwin’s position in relation to this is contained in Richard Dawkin’s The Blind Watchmaker (1986).

       A way to explain variability in a given species without dependence on random processes has been suggested by Derek Hough:

 

“The new theory which we shall name the theory of the self-developing genome states that the genome contains a program which work perfectly in a world which they have never seen. The first rule of the new theory states that evolution proceeds automatically and the second rule states that the new working models, or phenotypes, are designed by the genome without immediate reference to the outside world”. (Op. cit., p.47 )


The trouble with this theory is the lack of empirical evidence of the self-developing genome.

       Another critique of Darwnism states that species are more stable than is supposed – the so-called “stasis” hypothesis. This argues that when the environment changes species instead of adapting to the new conditions seek out a new environment. [7] While this does happen it can only happen if suitable environments exist elsewhere. If not Darwinian adaptation is the only possibility.

       While this kind of scientific critique of neo-Darwinism can make minor changes in the accepted theory they do not constitute of the fundamental critique of the insight of Darwin introduced in the Origin of Species.


The Descent of Man

       In the Origin Darwin had studiously avoided the origin of the human species. He probably wanted to avoid the vituperation he would have received from the religious community. Despite this his critics rightly concluded that the theory applied to humans as well. Shortly afterwards several writers published works applying Darwin’s principles to human evolution.

       So to state his position on this subject in 1871 Darwin published his second major work The Descent of Man and Selection in Relation to Sex, where he directly tackled the evolution of human beings or the species homo sapiens. The main change he introduced, if it indeed was a change, was to replace natural selection with sexual selection as the main engine of human differentiation.

       According to Darwin sexual selection “depends on the advantage which certain individuals have over others of the same sex and species, solely in respect of reproduction” (op.cit., p.209). However the notion of sexual selection has fared less well. The main difference is still between artificial selection (as in plant and animal breeding) and natural selection. Sexual selection shares characteristics of both. In the natural world it can be shown to be merely an aspect of natural selection.

       In this work Darwin set out to answer three questions. The first of these was “whether man, like every other species, is descended from a pre-existing form” (Descent, p.2). He answered this affirmatively, saying that humans must have descended from a less highly organized form, in fact, from a “hairy, tailed quadruped” (Descent, p. 231). [8] To prove his conjecture he carefully listed the physiological affinity of humans to various animal species, and even narrowed the immediate ancestors of humans to chimpanzees or gorillas. The concluding words of his book are: “Man still bears in his bodily frame the indelible stamp of his lowly origin”.

       What is remarkable is that Darwin was writing at a time when only a little physical evidence on human evolution had been found, and no hominid fossils had been unearthed outside of Europe. Subsequent discoveries have filled in the details and shown that the evolutionary path had not been as straight as Darwin had thought. Darwin has also been shown to be correct in his conjecture that man may have emerged first in Africa.

       While the first question was answered conclusively the answers to the other two questions were less than satisfactory. These questions were: “secondly the manner of his development, and thirdly the value of the differences of the so-called races of man” (ibid., p.2).

       By the “manner” of human development (after humans were set apart from the apes by evolution) Darwin meant the non-physical differences between humans and their progenitors. In particular he was intrigued how man developed a moral sense which he did not detect in animals. Chapters 3 - 5 was devoted to this question. Darwin traced it to two factors which emerged in the course of the evolution of man – a strong social instinct and intelligence.

       The first precondition for the emergence of a moral sense is that the species should develop social instincts (ibid. p. 232). Darwin noted that many animals too have a strong social sense. In the case of insects this was due to instinct, but in the case of birds, reptiles and mammals was generally connected with the need to propagate the species. In mammals (including humans) the young were born quite vulnerable and defenceless and thus needed a strong family organisation, which would lead to a form of social consciousness.

       Thus while a common nexus existed between humans and animals (at least the higher orders) on the question of the emergence of social bonds, there was an important difference. This is that humans have developed a moral sense while animals did not. Darwin had noted altruistic behaviour on the part of some animals but he did not equate this with a fully developed moral sense.

       This difference was due to the second factor, viz. the emergence of intelligence. This enabled humans to reflect on the past actions, approve actions of others, etc. The result was the emergence of a conscience, and ultimately an ethico-moral sense.

       Darwin’s ethics was based on the utilitarian ethics of Bentham and John Stuart Mill, which was generally based on the principle of the “greatest happiness of the greatest number”. Darwin believed that such a happiness maximising ethic will be developed by intelligent humans. [9] This part of the argument of the Descent has always remained problematical. Indeed it may be said that Darwin’s forays into the non-physical side of evolution has not generally withstood the test of time.

       Darwin’s treatment of the third question he sought to answer in the Descent (the “value” of racial differences between man) is the weakest part of this work. In his day anthropology had not developed a great deal, and since Darwin never left England after his voyage in the Beagle he had to rely on second-hand accounts. Given the unreliability of these accounts, not to mention the inevitable bias and racism of many anthropologists it is not surprising that his discussion of racial differences was very often wide off the mark. [10] Accordingly we shall ignore the third objective of Darwin, which in any case is not relevant to the main story of evolution, and to which he devoted only one chapter of his work.


The Religious Views of Darwin

       We have already said that there is very few references to religion in the two major works on evolution that Darwin wrote. This is surprising given that it was Darwin who was the first thinker to demolish conclusively the principal foundation of the Abrahamic religion.

       Darwin was not unaware of the religious implications of the theory he was expounding. In any case the clerical critique that he had to endure would not have allowed him to forget this aspect. Yet his observations on religion are contained mainly in the autobiography and in some of his correspondence, both published postumously. Darwin’s wife and some members of his family were Christians and this may explain his reluctance to deal with this matter.

       A better reason for this is given in a letter Darwin wrote in 1880 to Karl Marx, the other great radical nineteenth century thinker:

 

“It seems to me (rightly or wrongly) that direct arguments against Christianity and Theism hardly have any effect on the public; and the freedom of thought but will be promoted by that gradual enlightening of human understanding which follows the progress of science. I have therefore always avoided writing about religion and have confined myself to science”. [11]


       Despite the paucity of Darwin’s writings on religion it is possible to piece together the development of his views on the subject.

       When he joined the Beagle Darwin was still a Christian and he recalls “quoting the Bible as an unanswerable authority on some point of morality” to the amusement of his shipmates (Autobiography, p. 49) . Even so he was not a literalist in his reading of the Bible. But by the time he wrote his Autobiography he confesses to his agnosticism: “The mystery of the beginning of all things is insoluble to us; and I for one must be content to remain an Agnostic.” (op. cit., p.54). His friend and defender Huxley had introduced the term agnosticism, but at that time it was a polite way of proclaiming atheism.

       Darwin realised that God was a subjective construct and that other religions than Christianity could also validate their beliefs on subjective grounds:

 

“At the present day the most usual argument for the existence of an intelligent God is drawn from the deep inward conviction and feelings which are experienced by most persons. But it cannot be doubted that Hindoos, Mahomadans and others might argue in the same manner and with equal force in favour of the existence of one God, or of many Gods, or as with the Buddhists of no God.” (op. cit., p.52).


       Christian dogmas like eternal punishment for non-believers appalled Darwin:

 

“I can indeed hardly see how anyone can wish Christianity to be true; for if so, the plain language of the text seems to show that the men who do not believe, and this would include my Father, Brother and almost all my best friends, will be everlastingly punished. And this is a damnable doctrine” ( op.cit. , p.50).


       Darwin was puzzled why so “damnable” a doctrine should command the allegiance of so many persons many of considerable intelligence. Later he ascribes the belief in God to the conditioning of the minds of little children to the idea of God which in course of time could even become an instinct:

 

“Nor must we overlook the probability of the constant inculcation in a belief in God on the minds of children producing so strong and perhaps an inherited effect on their brains not yet fully developed, that it would be as difficult for them to throw off their belief in God, as for a monkey to throw off its instinctive fear and hatred of a snake.” (Autobiography, p. 54)


There may well be some truth in this conjecture of Darwin, which might explain the alleged “God centre” in the brain, or the fact that highly intelligent people, and even eminent scientists, find it difficult to give up the idea of God.


The Advocates of “Creation Science”

       Today those in the front rank of the irrational critique of Darwin are those who promote the creation myths given in the Bible. They could be divided into two groups – the literalists who advocate so-called “Creation Science” (and will be referred to here simply as ‘Creationists’), and the mainline Christian churches often seen as entertaining a “liberal” position on this question.

       The Creationists are well-funded groups in the West, like the Creation Research Institute, who have received recognition in some public educational jurisdictions. [12] They claim that evolution is merely a theory and should be taught along with the “theory” of creation as given in the Bible.

       There are several fallacies here. In the first place, as we have seen, evolution is not a theory but an empirical fact. Of course there are theories relating to what drives the evolutionary process. Darwin’s theory of natural selection is one of these theories, and is still the dominant one, but there are other hypotheses. Disputes between them are the normal stuff of scientific discourse and should be encouraged. Such criticisms far from impugning evolution as a fact actually validate it.

       Secondly there is neither a “fact” of Creation, nor a single “theory” of creation that could be presented as a counterfoil to evolution theory. What Creationists call their “theory” is the primitive myths retailed in the Bible. There are similar myths in other traditions and these are on the same level as the Biblical myth. Thus the claim of the Creationists that there is a stark alternative between “evolution theory” and the Biblical myth is a false one.

       The absurdities in the Biblical story are well known that they need not be elaborated here. There are several narratives of creation in the Bible. Biblical scholars have identified at least 3 sources for them called the P (for “Priestly”), J (for “Jahvist”) and E (for “Elohist”) documents. These give several versions of earlier Egyptian and Mesopotamian myths.

       Of the two versions of creation in Genesis the first (Gen 1.1 - 2.3) is from the P document. This contains many absurdities: light created before the sun, moon and stars, the sea before dry land, the sky as a dome over a flat earth, the “separation” of the waters, etc. The creation story here is not actually one of creation ex nihilio but of refashioning of preexisting things whose origin is not explained. Even taken as creation from nothing, the “theory” does not explain who created God. There is no answer to this except the claim that God is uncreated. But if God is uncreated then so could the universe be uncreated.

       The second story of creation (Gen 2.4 - 4.26) is from the J source. Now Adam is created before animals and even plants. This is the very opposite of the evolutionary sequence, and this story contradicts the first version. We need not go into the absurdities of this story.

       The age of the universe as postulated in the Biblical accounts, is a mere six to ten thousand years. [13] This is not supported by any evidence and merely shows the ignorance as to the real age of the universe current in the time the myths were composed.

       To explain away the irrefutable evidence given by the fossil record Creationists have relied on story of the Biblical flood, a legend traced to Mesopotamia, where the memory of an actual flood would have led to the exaggeration. Once again there are two versions of the flood derived from the P and the J sources. It would be tedious to enumerate the contradictions between these versions, and the absurdities involved in these account. .

       There are other tactics employed by Creationists such as questioning methods of dating fossils, particularly the radio-carbon method. [14] The “gaps” in the fossil record and the existence of “missing links” have been adduced to discredit the evidence for evolution. All these criticisms have been shown to be hollow.

       What is certain is that there is absolutely no science in “Creation Science”. The lack of any declared scientific methodology does not prevent the Creationists from calling their crude theology a science. It is merely a crude deception to appropriate the respect which true science has earned.


The Liberal Christian Position

       Most of the criticism by Humanists and Rationalists of the creation doctrine is confined to the literal version advocated by Creationists. They seem to ignore, and sometimes exonerate, the liberal Christian position as if this position has some greater validity than that of the literalists. This is not correct.

       The liberal position is extremely ambiguous. Evolution is taught in schools run by their churches, but at the same time their chapels and chaplains dole out the usual Christian prayers and invocations to their omnipotent and omniscient God. The contradiction in these two aspects seem to go unnoticed. The usual tactic is to say that the statements in the holy books are allegorical or metaphoric. However they have taken as literal for over 1500 years. Further more if they were allegorical the matter could have put beyond doubt by a simple statement to that effect. The liberal churches should say that the statements on their “revealed” texts are downright wrong, not that they are allegories of metaphors. Besides the fundamental dogma of Christianity assets that Jesus stoned for the sins of mankind right from the “original sin” in the Garden of Eden. This can only be validated on a literal reading of Genesis, not the metaphorical one which the liberal churches seem to be advocating.

       The attempt to develop a rapprochement with Darwin goes back to Darwin’s own time. After all Darwin was buried at Westminister Abbey and the leading prelates of the Anglican church attended his funeral. However only a few years before Bishop Wilberforce denounced Darwin’s theory in his famous debate on the origin of species with Huxley.

       The literalists may have some logic on their side. After all if their claims about their God are true then it is possible for this God to have also created the fossil record so as to deceive future scientists. The liberal Christians cannot resort to such a ruse. They are forced to fall back on their “metaphorical” interpretations of Biblical texts. But if these texts were not meant to be taken literally this would have been stated in the outset, or better still the “metaphorical” version alone could have been given. Besides if we leave the plain meaning of the texts aside then all kinds of contradictory metaphorical interpretations are possible. What the liberal churches have to admit is that the Biblical version is false, and the product of common ignorance, not of divine revelation. So long as they do not do this, the homage they pay to Darwin’s theory should be rejected as the exercise in duplicity that it is. On the other hand if they do admit that one of the principal claims about their God is false then the other claims which they pander can also be questioned. In fact the whole religious edifice they have built up can be questioned and will fall to the ground under this questioning.

       Some liberal theologians openly embrace the modern theory of evolution as giving a scientifically justified explanation of the origin of the various forms of life we observe today. Such clerical theorists like Spong and Holloway come to mind. But what is curious here is why they still call themselves Christian and go along with the symbolism and the rituals of the Christian faith?

       Darwin therefore has to be defended, not only against the puerile arguments of the Creationists, which is the easier task, but also against the fanciful positions taken by the liberal Christians. Some rationalists even enlist the liberal churches in refuting the Creationists. This is a mistaken strategy. The liberal Christians should be put on the same pedestal as the Creationists where they naturally belong.

 

The Vindication of Darwin

       The fundamental achievement of Darwin was to put the fact of evolution beyond doubt. He gave the finishing touch to a line of thinking which had been immanent in Western thinking for at least a century before him.

       It may be mentioned that the general notion of evolution has also been a part of Eastern thinking, both Indian and Chinese. It is particularly true of Buddhist cosmology where the cycles of world evolution and destruction are taken as granted and the Buddha said that an “ultimate beginning” of things cannot be discerned. In Hinduism too a similar process is conceived even though the Vedic deities are put in charge of the various phases. In the West there is general ignorance of classical Eastern notions of evolution, but this is not the place to address this question.

       The fact of evolution which Darwin established beyond doubt has not been refuted by any empirical evidence unearthed since his time. This has overwhelmingly supported the Darwinian conjecture. The other part of Darwin’s contribution to the subject are his theories of natural and sexual selection. As scientific propositions Darwin was well aware that they would in course of time be amended or supplemented. This is exactly what has happened and does not constitute a refutation of Darwin.

       The remarkable fact here is not the extent to which Darwin’s theoretical insights have had to be modified, but the extent they could be reconciled with later developments which Darwin did not even dream of. The most important of these are the application of Medelian genetics and of modern molecular biology. This gave rise to neo-Darwinism. The fact that this has now become the ruling orthodoxy in the biological sciences provides the ultimate vindication of Charles Darwin. 

 

BIBLIOGRAPHY

 

Darwin, Charles.  The Origin of Species by Means of Natural Selection. (1859). Ed. J.W.Burrow. Penguin Books, 1968.

Darwin, Charles.  The Descent of Man. (1871). London: Watts & Co., 1930.

de Beer, Gavin (ed). Charles Darwin: Autobiography (1875) Oxford University Press, 1975.

Whitfield, Philip. From So Simple a Beginning: a Book of Evolution. Macmillan, 1993.

Hough, Derek, Evolution: a Case for Stating the Obvious. Berkeley Publishing, 1997.