The Neo-Darwinist paradigm maintains that natural selection is the sole driving force in evolution. This paradigm is not only wrong, but untrue to Darwin’s theory of evolution which made room for Lamarck’s suggestion that acquired characteristics can also be inherited. The side-lining any research into Lamarckian evolution has stifled the fruitful work of generations of researchers, limiting our understanding of how inheritance really works, argues Denis Noble.
The Neo-Darwinist paradigm of evolutionary biology is almost defined by its view of inheritance. That view is that acquired characteristics cannot be inherited, and that the organism itself has no active role in the evolution of the species. One of its founders, August Weismann, created the break with the ideas of Charles Darwin in 1883, just a year following Darwin’s death in 1882. He did so by inventing the Weismann Barrier, which he claimed protects the germ-line, the future eggs and sperm, from any influences of use-disuse features acquired by the organism during its lifetime. He was therefore going against the Lamarckian idea of inheritance of acquired characteristics that Darwin had accepted and later expanded upon in his writings on heredity. There was no experimental evidence for Weismann’s idea. He even wrote that it was a “necessary” idea, whether or not any experiments supported it.
Weismann’s assertion that the inheritance of acquired characteristics is impossible was incorrect.
SUGGESTED READING The gene illusion By DenisNoble Had Darwin lived, we can be sure he would have promptly disagreed. For, during the last decade of his life, he worked assiduously with the young physiologist George Romanes on experiments designed to test his theory for how the inheritance of acquired characteristics could occur. In his 1868 book, The Variation of Animals and Plants under Domestication, he postulated the existence of tiny particles derived from the cells of the body that could transfer use-disuse memory to the germ line. To Darwin, there was no barrier.
Modern physiology has vindicated Darwin’s idea. The small vesicles, called exosomes or extracellular vesicles, poured out by all cells of the body can function precisely as Darwin’s idea proposed. They have now been proven to communicate such acquired characteristics as metabolic disorders, and sexual preferences, to the germ-line via small regulatory RNA molecules. We can therefore be sure that Lamarckian use-disuse memory can be passed across generations. Weismann’s assertion that the inheritance of acquired characteristics is impossible was therefore incorrect. The debate now centres on two questions: “how often this happens and, when it does, for how many generations do the changes persist?”
The standard neo-Darwinist defense against this clear break of the Weismann Barrier has been to suggest that it only happens in unimportant circumstances and persists for very few generations. There is assumed to be no permanent transmission. The DNA continues “hard” transmission while “soft” inheritance inevitably dies away.
This defence fails to recognise the great virtue of “soft” inheritance, which is precisely the possibility that it can be temporary.
Consider a species under extreme environmental stress, such as the Dutch population during the starvation winter of the 1940s in the Second World War. The inherited signs of that stress have now been passed down three generations, to the great-grandchildren of the 1940s population. The chances are that it will progressively die out as the later generations experience good nutrition. And so it should!
For it is not a good evolutionary strategy for temporary adjustments to environmental conditions to be rapidly embedded in the “hard” DNA inheritance process. “Soft” inheritance (as such epigenetic changes are called) is flexible and not necessarily assimilated into “hard” inheritance.
Even more shocking is the fact that subsequent generations of researchers have been discouraged from performing similar experiments on genetic assimilation.
So, how many generations are necessary for genetic assimilation to occur? In the 1950s, the developmental biologist, Conrad Waddington, performed experiments on the embryos of fruit flies. He discovered that around 14 generations were sufficient for “soft” inheritance to become assimilated into the species’ DNA. The process does not necessarily require new DNA sequences, though it does not exclude that possibility either. The process can work by the gene variants that, in combination, can ensure “hard” inheritance, to be brought together within individuals of the population. Selection via environmentally-induced use-and-disuse, or via organisms socially preferring certain variants, can drive the process.
Waddington’s experiments were important, recognised as such by Julian Huxley when he wrote the 1963 second Edition of his book Evolution: The Modern Synthesis. Waddington should therefore have been included in the founding group of the Neo-Darwinist Modern Synthesis developed in the 1930s and 1940s. Instead, he was deliberately excluded. Even more shocking is the fact that subsequent generations of researchers have been discouraged from performing similar experiments on genetic assimilation.
If you submit a Lamarckian inheritance project to standard grant bodies, you will be almost certain to receive a firm rejection. Such is the hold of the Neo-Darwinian paradigm on innovative ideas in evolutionary biology.
Such experiments need to be done to answer the question of how typical Waddington’s results may be. There is, in any case, no expectation that there should be a “magic” number of generations. Evolution is a continual “try-out” of possible strategies. Many processes are involved. We simply do not yet know how they may interact in different species. The evidence we have from a study of Darwin’s Galapagos finches is that the epigenetic and genetic characteristics both change as the species radiated out. It is difficult to know which came first. But it is more than likely that epigenetic changes occurred first. They can be rapid (in a single generation) and be expressed in a large fraction of the population, rather than waiting for a small mutation to slowly spread through the population.
Given the importance of the question, why have so few attempts been made on the genetic assimilation of “soft” inheritance since Waddington’s work? The answer is that funding organisations would not be willing to support such work. If you submit a Lamarckian inheritance project to standard grant bodies, you will be almost certain to receive a firm rejection. Such is the hold of the Neo-Darwinian paradigm on innovative ideas in evolutionary biology.
I know from my personal experience as a physiologist how firm that hold is. In 2016, I and four other scientists and philosophers organised a joint meeting of The Royal Society and The British Academy to discuss “New Trends in Evolutionary Biology”. It was organised under the Royal Society’s scheme for such DISCUSSION meetings, the whole point of which is to discuss novel, challenging, ideas. Yet as soon as the announcement of the November 2016 meeting appeared in February of that year, the President of The Royal Society received a strongly-worded protest letter signed by at least 20 other Fellows of The Royal Society asking that the meeting should no longer be held as a meeting at the society’s premises. For good measure, the letter was deeply insulting in what it contained concerning my credentials for holding such a meeting.
I would like readers of this article to ponder the significance of that protest. The Royal Society’s Latin motto is NULLIUS IN VERBA, roughly, “take no one’s word for it”. In other words, perform the experiments. This was the Royal Society's 17th-century founders’ deep commitment to the experimental approach. Yet, here was a large group of Fellows proposing to stop others from discussing new ideas! Fortunately, my co-organisers and the two Academies held firm. The meeting went ahead, was a complete sell-out, and resulted in a valuable publication in one of the Royal Society’s journals.
This situation is serious since I also have another experience that confirms the tight hold of which I am writing. I have been the examiner of PhD theses by young scientists performing precisely the experiments designed to test the extent and persistence of soft inheritance. The problem has always been to attract funding. It is also a problem to find suitable examiners. Very few physiologists with the relevant expertise are knowledgeable about evolutionary biology. Three generations of physiologists have now been educated to believe that their subject is not relevant to evolution. Charles Darwin would never have agreed with that.
It is high time this disgraceful situation should be brought to an end. If we don’t encourage the young to be bold and challenge accepted wisdom, we are lost.