The Inheritance of Acquired Characteristics

Extracts from “Lamarck’s Due, Darwin’s Luck”

The inheritance of acquired characteristics is a theoretical mechanism by which a species can change, over many generations, into a different species by progressively accumulating minor changes caused by habits and external circumstances, including diet. For example, if, during his gestation and growth, a male hominid developed a bigger brain due to a rich diet than he would have done without the rich diet, that is an acquired characteristic. If he got together with a similarly-affected female hominid and any of their offspring had a bigger brain than it would have done if its parents had not had rich diets, that is the inheritance of an acquired characteristic, however slight the increase in brain size was. Similarly, if a group of stooping, hairy apes became more upright and less hairy as a consequence of standing in sea water, and any of their offspring were naturally more upright or less hairy than they would have been if their parents had not spent time standing in sea water, that is the inheritance of acquired characteristics. If a group of hominids moved to an environment where they were exposed to less strong sunlight than they had been, and they became lighter-skinned as a consequence, with an incremental accumulative effect over the generations, that is due to the inheritance of an acquired characteristic.

The inheritance of acquired characteristics is a logical necessity for any evolutionary system which relies upon changes made in response to experience. Otherwise every generation would have to go back to the same Square One that their parents had started at. As a mechanism, it was made famous by the French evolutionist, Lamarck, but it was in fact the assumed mechanism by which lasting change happened for virtually all pre-Darwinian evolutionists. Ironically, in the light of what he would become famous (or infamous) for, Lamarck attached little importance to the inheritance of acquired characteristics; that was just a necessary assumption. His emphasis was upon the acquisition of characteristics, which is not now seriously disputed in principle, rather than their inheritability, which is. I said ‘pre-Darwinian’ evolutionists, but that should really have included Darwin. That’s right – in modern-day terms, Darwin was a Lamarckist. Present-day Darwinists like to ignore that fact or, if they do acknowledge it, say it was an understandable aberration. Darwin himself chose to play it down, but the fact remains that he believed in the inheritance of acquired characteristics as being one of the sources of variations by which Natural Selection was aided.

The reasons why Darwin believed in the inheritance of acquired characteristics were partly because he was impressed, and convinced, by numerous apparent proofs, but mainly because he couldn’t conceive of anomalies such as flightless birds being caused by anything other than the accumulative, inherited effects of disuse of organs. This was an entirely logical stance, given Darwin’s beliefs in the rarity of specific random variations, their minimal effect, and natural culling. If you take a group of proto-ostriches which were still able to fly, but didn’t, any individual which incurred a random variation which made it less able to fly would not find that detrimental, but neither would it have any advantage over all the other proto-ostriches, who wouldn’t be punished for still being able to fly, so the random variation would stand no chance of becoming universal to the species. Logically, Darwin could also see that, if disuse diminishes organs, use must develop them. His most unequivocal early support for the inheritance of acquired characteristics came in the form of his speculations as to the mechanism of heredity, called the hypothesis of Pangenesis, as explained in his 1868 book, “The Variation of Animals and Plants under Domestication”, the two Volumes of which basically constituted the first two chapters of his 1850s tome:

How, again, can we explain to ourselves the inherited effects of the use or disuse of particular organs?….How can the use or disuse of a particular limb or of the brain affect a small aggregate of reproductive cells, seated in a distant part of the body, in such a manner that the being developed from these cells inherits the characters of either one or both parents? Even an imperfect answer to this question would be satisfactory.

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In variations caused by the direction of changed conditions, whether of a definite or indefinite nature, as with the fleeces of sheep in hot countries, with maize grown in cold countries, with inherited gout etc., the tissues of the body, according to the doctrine of pangenesis, are directly affected by the new conditions, and consequently throw off modified gemmules, which are transmitted with their newly-acquired peculiarities to the offspring. On any ordinary view it is unintelligible how changed conditions, whether acting on the embryo, the young or adult animal, can cause inherited modifications. It is equally or even more unintelligible on any ordinary view, how the effects of the long-continued use or disuse of any part, or the changed habits of the body or mind, can be inherited. A more perplexing problem can hardly be proposed; but on our view we have only to suppose that certain cells become at last not only functionally but structurally modified; and that these throw off similarly modified gemmules.

It has to be said that his hypothetical gemmules have never been observed and that Pangenesis proved only to be a debating point and was never generally accepted. Nonetheless, Darwin was quite content to maintain belief in the inheritance of acquired characteristics, as may be demonstrated by the following passage about blushing from his 1873 book, “The Expression of the Emotions in Man and Animals”:

It is a rather curious question why, in most cases the face, ears, and neck alone redden, inasmuch as the whole surface of the body often tingles and grows hot. This seems to depend, chiefly, on the face and adjoining parts of the skin having been habitually exposed to the air, light, and alternations of temperature, by which the small arteries not only have acquired the habit of readily dilating and contracting, but appear to have become unusually developed in comparison with other parts……Of all parts of the body, the face is most considered and regarded, as is natural from its being the seat of expression and the source of the voice. It is also the chief source of beauty and of ugliness, and throughout the world is the most ornamented. The face, therefore, will have been most subjected during many generations to much closer and more earnest self-attention than any other part of the body; and in accordance with the principle here advanced we can understand why it should be the most liable to blush.

In the Preface to the Second Edition of “The Descent of Man”, he wrote:

I may take this opportunity of remarking that my critics frequently assume that I attribute all changes of corporeal structure and mental power exclusively to the natural selection of such variations as are often called spontaneous; whereas, even in the first edition of the ‘Origin of Species’, I distinctly stated that great weight must be attributed to the inherited effects of use and disuse, with respect both to the body and mind. I also attributed some amount of modification to the direct and prolonged action of changed conditions of life.

In fact, Darwin’s belief in the inheritance of acquired characteristics became increasingly emphasised right up to his death. In the final edition of “The Origin of Species”, he even went so far as to say, “It appears probable that disuse has been the main agent in rendering organs rudimentary.” Part of the reason for this increasing emphasis was in response to a technical problem that his theory had run into as a result of an 1867 review of “The Origin….” by a Scottish engineer, Henry Charles Fleeming Jenkin. One of the most oft-quoted passages from “The Origin of Species” is this:

If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.

Not only does this illustrate a prevalent view in science that a single error can invalidate a life’s work, but it has also been used as a starting point by anti-Darwinists. Creationists devoted a lot of attention to the eye as a complex organ that must have been purposefully designed rather than created by chance. In doing so, they played right into the Evolutionists’ hands. There were, however, more worrying refutations. Though the following argument did not necessarily relate to complex organs, and it was by no means clinching, it set the tone of reasoned debate. In order to defeat Darwin’s theory, the arguments would need to be evidential and technical rather than based on religious indoctrination or philosophical distaste.

The ‘commonsense’ view of the time was that reproduction represented blending of characteristics. It was slightly haphazard, as evidenced by the differences between brothers or sisters and the occasional tendency of a perceptible characteristic to skip a generation, but the overall trend was towards evening out. Darwin had attached much attention to the issue of Artificial Selection, as practised by dog-breeders and pigeon-fanciers, from which the evidence was that any characteristic that had been purposefully bred into an animal was easily lost through mongrelisation. If both breeding animals have the same characteristic, it can be preserved and even accentuated, but if only one of the breeding pair has it, it can be diminished or swamped. This became known as the Law of Regression towards Mediocrity. The implicit premise of Darwin’s theory was that any random variation had to happen to only one individual, known as a ‘sport’ if the variation was detectable, in the first instance. That individual would have to breed with a normal member of the species. Therefore, in contradiction to the theory of Natural Selection, any random variation would tend to be blended out rather than developed, however beneficial it was; any benefit that a variation conferred would reduce over time rather than increase. That was what Jenkin’s review pointed out, citing the example of what would happen if a white man were to live and breed in a black community.

Darwin’s answer to this was to reassert his belief in the inheritance of acquired characteristics. By that mechanism, favourable characteristics could spread, and grow, rapidly; due to the same changed conditions or to imitation, many individuals within a breeding group could acquire the same characteristic. In other words, all Darwin’s theory was doing was incorporating the guiding system of Natural Selection into Lamarck’s theory. The only real difference between them was Lamarck’s emphasis on responsive adaption and Darwin’s emphasis on natural culling. That’s not just my view; it had also become the view of Darwin’s good friend, Sir Charles Lyell. So Natural Selection was really just acting on the consequences of habits and changes of use? Yes, but there also had to be a random source of inheritable novelty, argued Darwin, under changed conditions of existence. So, what Darwin’s theory now resembles is “The Control of Species Development by Means of Natural and Sexual Selection, or The Preservation of Favourable Acquired Characteristics and Occasional Random Novelty Features”. I wish Darwinism had stayed like that. I would have been a loyal supporter. I would quite happily call myself a Darwin-as-Darwin-intended-it-ist. Like many an evolutionary dissident, then and now, I have no problem whatsoever with Natural Selection as such.

After his death, the doctrine of Darwinism became censored in respect of the inheritance of acquired characteristics, though his writings weren’t. The reason why Darwinism became censored was because of two German theories and an Austrian ‘discovery’. The first, known as Cell Theory, said that every cell was produced by the division of a previous cell, and a consequence of that was that ‘experience’ could only be passed on to direct descendants. It was followed by August Weismann’s Germ-plasm Theory, in which he claimed that the germ-plasm, which was what he called the stuff that the nuclei of sperms, eggs and seeds were essentially made from, took a continuous line of descent without being affected by the organisms which it generated (or generated it). In other words, his sperms could not have been tampered with either by him or by any of his ancestors, because all the body cells, including the germ-line cells, were made by successive divisions of the original fertilised egg. The germ-line cells became differentiated during embryology and could not thereafter be affected by the somatic (body) cells. That became known as Weismann’s Barrier – information could flow from fertilised egg to organism, but not vice versa – and, in his view, it made the inheritance of acquired characteristics logically impossible. Thus it was Weismann, more than any other living person, whose intervention led to the divorce between Lamarckism and Darwinism after Darwin’s death, and the consummation of his proposition would lead to the birth of neo-Darwinism.

Weismann’s proposition was vindicated in his own lifetime by the rediscovery in 1900 of a paper written and published in 1865 by an Austrian monk, Gregor Mendel who became abbot of his monastery in what is now the Czech Republic in 1868. He had studied science in Vienna after becoming a priest, and indulged his passion for horticulture at his monastery, where the growing of food was an important aspect of life. It has been said about Mendel that, as a celibate monk, he possibly had more reason than most to notice that the result of reproduction between a man and a woman was either a man or a woman and not an hermaphrodite. He observed much the same type of quantisation in the hybrid peas he cultured, and he reported his results in his famous paper. Essentially, he noted that reproduction does not result in blending of characteristics but in the presence or absence of simple characteristics. His hybrid peas were distinctly either one type or the other, not halfway between. Most significantly, he discovered that hereditary factors could be dominant, in which case they always showed, or recessive, in which case they only showed in the absence of a dominant factor. He didn’t fully understand his results, or attach that much significance to them, so he couldn’t have had an inkling of the fact that he would later become regarded as the father of genetics.

As a consequence of all of the above, Lamarckian inheritance became discredited, and even vilified, throughout most of the 20th century. The tenets of 19th century science, combined with the increasing evidence concerning the essential contents of the germ-plasm, the chromosomes, made Lamarckian inheritance inexplicable. Put simply, the DNA sequences within the genes within the chromosomes cannot be changed as a consequence of experience. During the latter half of the 20th century, a growing number of dissidents began to question whether those genes were, in themselves, responsible for characteristics. Some began to wonder whether it was the expression of genes, rather than merely their existence, that controlled development. Little was known about the control of gene expression. In the 21st century, epigeneticists have discovered that the expression of genes can be altered in an inheritable way. In other words, the inheritance of acquired characteristics has been an important, if not the most important, factor in the evolution of species. Lamarck was right. So was Darwin, except perhaps in his emphasis.

Throughout the entire evolution debate of the past two centuries, there has never been a shred of philosophically-rigorous evidence against the inheritance of acquired characteristics, and the empirical evidence has always been in favour of it. There are mountains of circumstantial evidence from nature which can be explained much more easily by Lamarckism than by neo-Darwinism. There have been numerous experiments done which have demonstrated the apparent inheritance of acquired characteristics, including those by Edouard Brown-Sequard and Karl Semper in the 19th century, and those of Paul Kammerer and Conrad Waddington in the 20th century. Recently, the phenomenon of second-generation Thalidomide symptoms can only be explained by reference to non-genetic inheritance, and some behind-the-scenes scientists have been reporting new evidence of Lamarckian inheritance, including the long-term consequences of the Dutch Hunger Winter of 1944-45.

What is still in some doubt, to the point of emphatic denial on the part of loyal neo-Darwinists, is the mechanism by which acquired characteristics become inherited. For more insight into that, I refer you to my essays on Rupert Sheldrake and “Lamarckian Inheritance from Epigenetics”.