“Molecular mechanisms that generate biological diversity are rewriting ideas about how evolution proceeds”. I couldn’t help noticing how similar that sounds to what I was saying in my Nature article last spring, “Celebrate the unknowns”. Some people were affronted by that – although other responses, like this one from Adrian Bird, were much more considered. But this is the claim put forward by Susan Rosenberg and Christine Queitsch in an interesting commentary in Science this week. They point out (as I attempted to) that the “modern synthesis” so dear to some is in need of some modification.
“Among the cornerstone assumptions [of the modern synthesis]”, say Rosenberg and Queitsch, “were that mutations are the sole drivers of evolution; mutations occur randomly, constantly, and gradually; and the transmission of genetic information is vertical from parent to offspring, rather than horizontal (infectious) between individuals and species (as is now apparent throughout the tree of life). But discoveries of molecular mechanisms are modifying these assumptions.” Quite so.
This is all no great surprise. Why on earth should we expect that a theory drawn up 80 or so years ago will remain inviolable today? As I am sure Darwin expected, evolution is complex and doesn’t have a single operative principle, although obviously natural selection is a big part of it. (I need to be careful what I say here – one ticking off I got was from a biologist who was unhappy that I had over-stressed natural selection at the molecular level, which I freely confess was a slight failure of nerve – I have found that saying such things can induce apoplexy in folks who see the shadows of creationism everywhere.) My complaint is why this seemingly obvious truth gets so little airplay in popular accounts of genetics and evolution. I’m still puzzled by that.
I realise now that kicking off my piece with ENCODE was something of a tactical error (even though that study was what began to raise these questions in my mind), since the opposition to that project is fervent to the point of crusading in some quarters. (My own suspicion is that the ENCODE team did somewhat overstate their undoubtedly interesting results.) Epigenetics too is now getting the backlash for some initial overselling. I wish I’d now fought harder to keep in my piece the discussion of Susan Lindquist’s work on stress-induced release of phenotypic diversity (S. Lindquist, Cold Spring Harb. Symp. Quant. Biol. 74, 103 (2009)), which is mentioned in the Science piece – but there was no room. In any case, this gives me the impetus to finally put the original, longer version of my Nature article online on my web site – not tonight, but imminently.