What explains the dogmatism and persistence of neo-darwinism?
When the history of neo-Darwinism gets written it will need to answer this question. I am not a historian. The answers I give here are tentative. They could be leads for serious historians of science to follow up. I also highlight two brilliant scientists, Waddington and McClintock, whose work should not have been neglected.
The progress of science is not Popperian
Despite the great influence of Popper, single contrary observations rarely destroy a strongly established theory. The tendency is to fix theories, extend them, even to redefine their entities, in ways that allow the contrary observations to be absorbed. This is what happened to Waddington’s work. If they can’t be absorbed in this way, they are sidelined as anomalies. This nearly happened to McClintock until she was awarded the Nobel Prize for discovering mobile genetic elements (jumping genes). It is more often the accumulation of many forms and examples of contrary evidence that persuades people to change. I think we are at that point now in the case of neo-Darwinism. There are exceptions to all the central assumptions, and in the case of the inheritance of acquired characteristics the exceptions are becoming a flood of evidence. Moreover, the central element of the theory, the gene, is no longer easy to define. All those functional RNAs also act as ‘genes’. The marking of the genome and chromatin also play a role in inheritance. That is the reason why a growing number of scientists admit that a major rethink is already happening.
Conrad Waddington in 1946 (left, from The Royal Society picture library) and his diagram of the epigenetic landscape (right, from The Strategy of the Genes, 1957). Genes (solid pegs at the bottom) are viewed as parts of complex networks so that many gene products interact to produce the phenotypic landscape (top) through which development occurs. Waddington’s insight was that new forms could arise through new combinations to produce new landscapes in response to environmental pressure, and that these could then be assimilated into the genome. Waddington was a systems biologist in the full sense of the word. If we had followed his lead many of the more naïve 20th century popularizations of genetics and evolutionary biology could have been avoided.
Left: Barbara McClintock in her laboratory in 1947 (Smithsonian Institute Archives).
“In the future attention undoubtedly will be centered on the genome, and with greater appreciation of its significance as a highly sensitive organ of the cell, monitoring genomic activities and correcting common errors, sensing the unusual and unexpected events, and responding to them, often by restructuring the genome. We know about the components of genomes that could be made available for such restructuring. We know nothing, however, about how the cell senses danger and instigates responses to it that often are truly remarkable.” (McClintock, Barbara. 1984 The significance of responses of the genome to challenge. Science 226, 792-801.)
McClintock clearly understood the correct direction of causality in relation to the genome. Characterising the genome as “a highly sensitive organ of the cell” was her great insight. It is as foolish to regard the genome as the active cause of the organism as it would be to say that the pipes of an organ play the music!
Right: giving Nobel Prize lecture in 1983 (NIH)
Theories of evolution became an issue during the Cold War. Those, like Waddington, who found evidence for the inheritance of acquired characteristics were thought in some way to be associated with Lysenkoism, a Soviet era school that denied Mendelian inheritance. Waddington was not even allowed to visit the USA. His work was virtually ignored in the USA, and was eventually sidelined in the UK. He saw himself as a Darwinist, but not as a neo-Darwinist. I think it is shameful that such a brilliant scientist was side-lined, just as I think it is shameful that Lamarck was virulently denigrated. Anyone who thinks that science is neutral, and is not influenced by politics, should answer the question: how did these injustices happen?
It is said that nearly 50% of the population of the USA do not accept the theory of evolution. Some are called creationists since they believe in various forms of creation, either literally as described in Genesis, or in a variety of more modern ideas of creationism. Some also espouse the ideas of Intelligent Design (ID). Both the creationists and the supporters of ID tend to take every example of a break with neo-Darwinism as a vindication of their views. Some have done the same with my article, despite the fact that I make it clear that I am arguing for a return to a “more nuanced, less dogmatic view of evolutionary theory (see also Muller, 2007; Mesoudi ¨ et al.2013), which is much more in keeping with the spirit of Darwin’s own ideas than is the Neo-Darwinist view.”
Muller GB (2007). Evo–devo: extending the evolutionary synthesis. Nat Rev Genet 8, 943–949 http://www.ncbi.nlm.nih.gov/pubmed/17984972
Mesoudi A, Blanchet S, Charmentier A, Danchin E, Fogarty L, Jablonka E, Laland KN, Morgan TJH, Mueller GB, Odling-Smee FJ & Pojol B. (2013). Is non-genetic inheritance just a proximate mechanism? A corroboration of the extended evolutionary synthesis. Biological Theory 7, 189–195. http://link.springer.com/article/10.1007/s13752-013-0091-5
One way to view the dogmatic nature of neo-darwinism as it is often presented in public is to see it as a reaction to the dogmatism of the creationists. The ‘uncertain’ (in the sense of lacking reason) faith in creationism is replaced by the ‘certainties’ of science. But there is a conflation here of very different degrees of certainty in science. There can’t be much doubt about the fact that life on earth has evolved. There is much less certainty about the mechanisms. Unlike Darwinism (Darwin knew nothing of mechanisms, genes were not known), neo-darwinism proposes the exclusion of many mechanisms that have in fact now been found to occur in nature. Adopting the ‘certainty’ of evolution to clothe the ‘uncertainty’ of particular theories about mechanisms has been the cause of many problems in public debate on evolution. It is perfectly possible to defend the virtual certainty that life has evolved while debating in the usual argumentative scientific way the uncertainties surrounding the question of mechanisms. The truth is that amongst the many mechanisms now known we know very little about which were prevalent in evolution. The answer is likely to be that different mechanisms were dominant at different stages. Evolution itself evolves.
See also the item on The Language of Neo-darwinism where the discourse of neo-darwinism is analysed.