Well, since the tussle about epigenetics involves Brits, they’re really too polite to engage in a “smackdown.” Let’s just call it a “kerfuffle.” Nevertheless, two scientists have an enlightening 25-minute discussion about epigenetics at the Guardian‘s weekly science podcast (click the link and listen from 24:30 to 49:10). If you’re science friendly and have an interest in this ‘controversy,’ by all means listen in. It’s a good debate about whether “Lamarckian” inheritance threatens to overturn the modern theory of evolution.
Readers know how I feel about the epigenetics “controversy.” “Epigenetics” was once a term used simply to mean “development,” that is, how the genes expressed themselves in a way that could construct an organism. More recently, the term has taken on the meaning of “environmental modifications of DNA,” usually involving methylation of DNA bases. And that is important in development, too, for such methylation is critical in determining how genes work, as well as in how genes are differentially expressed when they come from the mother versus the father.
But epigenetics has now been suggested to show that neo-Darwinism is wrong: that environmental modifications of the DNA—I’m not referring to methylation that is actually itself coded in the DNA—can be passed on for many generations, forming a type of “Lamarckian” inheritance that has long been thought impossible. I’ve discussed this claim in detail and have tried to show that environmentally-induced modifications of DNA are inevitably eroded away within one or a few generations, and therefore cannot form a stable basis for evolutionary adaptation. Further, we have no evidence of any adaptations that are based on modifications of the DNA originally produced by the environment.
In the Guardian show, the “Coyne-ian” position is taken by Dr. George Davey Smith, a clinical epidemiologist at the University of Bristol. The “epigenetics-will-revise-our-view-of-evolution” side is taken by Dr. Tim Spector, a genetic epidemiologist at King’s College. Smith makes many of the points that I’ve tried to make over the past few years, and I hope it’s not too self-aggrandizing to say that I think he gets the best of Spector, who can defend the position only that epigenetic modification is important within one generation (e.g., cancer) or at most between just two generations.
But listen for yourself. These guys are more up on the literature than I am, and I was glad to see that, given Smith’s unrebutted arguments, neo-Darwinism is still not in serious danger. (I have to say, though, that I’d like to think that if we found stable and environmentally induced inheritance that could cause adaptive changes in the genome, I’d be the first to admit it.)