The neo-Darwinist paradigm holds that natural selection is the sole driving force of evolution. This paradigm is not only wrong, but contrary to Darwin’s theory of evolution which gave way to Lamarck’s suggestion that acquired characteristics can also be inherited. The sidelining of all research on 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. This 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 after Darwin’s death in 1882. He did so by inventing the Weismann barrier, which he claimed , protects the germ line, future eggs. and sperm, from any influence of use-non-use characteristics acquired by the organism during its lifetime. He therefore went against the Lamarckian idea of heredity of acquired characteristics that Darwin had accepted and later developed in his writings on heredity. There was no experimental evidence for Weismann’s idea. He even wrote that it was a “necessary” idea, whether experiments support it or not.
Weismann’s assertion that inheritance of acquired characteristics is impossible was incorrect.
The genetic illusion
If Darwin had lived, we can be sure he would have quickly disapproved. For during the last decade of his life he worked diligently with the young physiologist George Romanes on experiments designed to test his theory of how 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 body cells that could transfer use-disuse memory to the germ line. For Darwin, there were no barriers.
Modern physiology has confirmed Darwin’s idea. The small vesicles, called exosomes or extracellular vesicles, shed by every cell in the body can function precisely as Darwin’s idea proposed. They have now been shown to communicate acquired characteristics such as metabolic disorders and sexual preferences to the germ line via small regulatory RNA molecules. So we can be sure that Lamarckian use-disuse memory can be passed down through the generations. Weismann’s claim that inheritance of acquired characteristics is impossible was therefore incorrect. The debate now revolves around two questions: “how often does this happen and, when does it happen, for how many generations do the changes persist?”
The standard neo-Darwinist defense against this clean break in the Weismann barrier has been to suggest that it occurs only in unimportant circumstances and persists for very few generations. It is assumed that there is no permanent transmission. The DNA continues the “hard” inheritance while the “soft” inheritance inevitably dies.
This defense ignores the great virtue of “soft” inheritance, which is precisely the possibility that it may be temporary.
Consider a species under extreme environmental stress, such as the Dutch population during the famine winter of the 1940s during World War II. The inherited signs of this stress have now been passed down through three generations, to the great-grandchildren of the 1940s population. There is a good chance that it will gradually disappear as future generations benefit from good nutrition. And so it should!
For it is not a good evolutionary strategy that temporary adjustments to environmental conditions are quickly built into the “hard” DNA inheritance process. “Soft” inheritance (as such epigenetic changes are called) is flexible and not necessarily equated with “hard” inheritance.
Even more shocking is the fact that subsequent generations of researchers were discouraged from performing similar experiments on genetic assimilation.
So how many generations are needed for genetic assimilation to occur? In the 1950s, developmental biologist Conrad Waddington performed experiments on fruit fly embryos. He discovered that about 14 generations were enough for the “soft” heritage to assimilate into the DNA of the species. The process does not necessarily require new DNA sequences, although it does not rule out that possibility either. The process can work through genetic variants which, in combination, can ensure “hard” heredity, to be gathered within individuals in the population. Selection via environmentally induced use and non-use, or via organisms socially preferring certain variants, can drive the process.
Waddington’s experiments were important, recognized as such by Julian Huxley when he wrote the second edition of his book in 1963 Evolution: 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 were discouraged from performing similar experiments on genetic assimilation.
If you submit a Lamarckian legacy project to the standard granting agencies, you are almost certain to receive a firm rejection. Such is the grip of the neo-Darwinian paradigm on innovative ideas in evolutionary biology.
Such experiments must be done to answer the question of how typical Waddington’s results may be. There is no expectation that there will be a “magic” number of generations. Evolution is a continuous “testing” of possible strategies. Many processes are involved. We just don’t know yet how they might interact in different species. The evidence we have from a study of Darwin’s Galapagos finches is that epigenetic and genetic characteristics both change as the species radiates. It’s hard to know which came first. But it’s more than likely that epigenetic changes happened first. They can be quick (within a single generation) and express themselves in a large part of the population, rather than waiting for a small mutation to slowly spread through the population.
Given the importance of the question, why have there been so few attempts to genetically assimilate ‘soft’ inheritance since Waddington’s work? The answer is that funding agencies would not be willing to support such work. If you submit a Lamarckian legacy project to the standard granting agencies, you are almost certain to receive a firm rejection. Such is the grip of the neo-Darwinian paradigm on innovative ideas in evolutionary biology.
I know from personal experience as a physiologist how firm this grip is. In 2016, myself and four other scientists and philosophers organized a joint meeting of the Royal Society and the British Academy to discuss “Emerging Trends in Evolutionary Biology”. It has been organized as part of the Royal Society’s program for such DISCUSSION meetings, the purpose of which is to discuss new and challenging ideas. Yet as soon as announcement of the November 2016 meeting appeared in February of that year, the President of the Royal Society received a strong letter of protest signed by at least 20 other Royal Society members asking that the meeting is no longer held as a meeting on the premises of the company. For good measure, the letter was deeply insulting in what it contained regarding my credentials for holding such a meeting.
I would like the readers of this article to reflect on the significance of this protest. The Latin motto of the Royal Society is NULLIUS IN VERBA, basically, “Take no one’s word for it”. In other words, perform the experiments. This was the deep commitment of the founders of the Royal Society in the 17th century to the experimental approach. Yet there was a large group of fellows offering to keep others from discussing new ideas! Fortunately, my co-organizers and the two Academies held on. The meeting went ahead, sold 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 which confirms the influence of which I am writing. I have been the examiner of doctoral theses of 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 difficult to find competent examiners. Very few physiologists with relevant expertise are familiar with evolutionary biology. Three generations of physiologists have now been educated to believe that their subject is evolutionarily irrelevant. Charles Darwin would never have agreed with that.
It is high time to put an end to this shameful situation. If we don’t encourage young people to be bold and challenge conventional wisdom, we are lost.