Last week I highlighted a piece on epigenetics by Florian Maderspacher, an editor at Current Biology. (For this post I’ll define “epigenetics” as “inheritance that transcends generations but is not based on changes in DNA sequence”.) Florian decried all the current hype about epigenetics—that is, the idea that this phenomenon will revolutionize our view of evolution—and mentioned its connection to Trofim Lysenko, the Soviet agronomist who wrought immense havoc on Russian science and agriculture with his misguided notion that environmental modifications of crops could become permanently fixed in their genes.
I agree with much of what Maderspacher said (I’ve posted on this before): the “evolutionary” notion of epigenetics is an overblown construct with little empirical backing, and seems largely to further the career aspirations of its advocates.
Now the two biggest drivers of the “evolutionary epigenesis” bandwagon, Eva Jablonka and Marion Lamb, have replied in Current Biology, and Maderspacher responds (scroll down when you get to the page). Jablonka and Lamb object to the Lysenko analogy as tarring their new paradigm with the ghosts of pseudoscience past. Maderspacher responds:
Of course, tastes are allowed to differ, but I firmly believe that in scientific discourse, which is not categorically different from other forms of discourse, there is some room for stylistic freedom, all the more in an opinion piece such as mine. If you compare my six-column piece to the amount of paper that has been filled with sensationalism about epigenetics, it seems legitimate that the ‘small dog’ barks a little louder, as it were. (that in the interim both science and nature neuroscience have run special issues on epigenetics is a case in point)
I chose Lysenko as an admittedly extreme figurehead, because he exemplifies what can happen if political interpretation gets in the way of scientific rigour. In particular I was interested in the interpretation the public brings towards a rather esoteric field of molecular biology and genetics. Why are people so interested in epigenetics? Because they like to see it as a liberation (”victory over the genes”), and this is exactly where Lysenko was coming from. I wanted to expose this distorted reasoning. To imply that I equate the study of environmental influences on heredity with Lysenkoism is, frankly, untenable.
But of course this part of the kerfuffle is about framing and tone. The more important thing is the science behind the epigenetics hype. And I maintain, as I have for a while, that there is simply no good data supporting the idea of non-genetically based and transgenerational inheritance as an important factor in evolution. I’ve read nearly all of Jablonka and Lamb’s papers, and they keep recycling the same tired old examples (mouse fat and toadflax) to show how drastically epigenetic inheritance can alter our view of neo-Darwinian evolution. They have not said anything new for a long time.
Their arguments are unconvincing for a number of reasons. Epigenetic inheritance, like methylated bits of DNA, histone modifications, and the like, constitute temporary “inheritance” that may transcend one or two generations but don’t have the permanance to effect evolutionary change. (Methylated DNA, for instance, is demethylated and reset in every generation.) Further, much epigenetic change, like methylation of DNA, is really coded for in the DNA, so what we have is simply a normal alteration of the phenotype (in this case the “phenotype” is DNA) by garden variety nucleotide mutations in the DNA. There’s nothing new here—certainly no new paradigm. And when you map adaptive evolutionary change, and see where it resides in the genome, you invariably find that it rests on changes in DNA sequence, either structural-gene mutations or nucleotide changes in miRNAs or regulatory regions. I know of not a single good case where any evolutionary change was caused by non-DNA-based inheritance.
Maderspacher hits the nail squarely:
This leads to the second line of criticism, my allegedly distorted portrayal of epigenetics as a scientific discipline. I happily admit that I am not an epigenetics expert, by any stretch of the imagination. I would even argue that it can sometimes be helpful to have a view from afar, from someone who has no personal stakes in the matter. And I certainly agree that paradigms (and terms) in biology shift all the time. But they shift when new empirical data call the pervious paradigm into question. In the case of DNA and histone modification, I cannot see how they call for a change in our view of genetics. As for epigenetic inheritance, I am aware that there are numerous examples and mention some in the piece. This is interesting biology and deserves attention. But does it call for a paradigm shift? Only time will tell, I guess.
I’m talking in Medellin, Colombia next week about all of the new “challenges” to neo-Darwinism, and epigenesis is among them. Relevant to the increasing cacophony from the “Darwin-was-wrongers,” I have two quotes. The first is from evolutionary biologist Doug Futuyma:
One has to have a certain degree of reservation about claims that are made on the basis of one or two examples that are going to be a major challenge or a new expansion. Otherwise you’re talking about jumping on one bandwagon after another.
The second is from my Ph.D. advisor Dick Lewontin:
. . . scientists are always looking to find some theory or idea that they can push as something that nobody else ever thought of because that’s the way they get their prestige. . . .they have an idea which will overturn our whole view of evolution because otherwise they’re just workers in the factory, so to speak. And the factory was designed by Charles Darwin.
Florian is much more polite than I am, but as I age I become less reluctant to broach the charge of careerism. Being ambitious is not inherently bad: all scientists secretly wish to get a big name and be lionized among their peers. A desire for renown—to be first with the goods—has motivated much of the best science we have. But there’s a good way and a bad way to get famous. The good way is to produce solid, interesting data and avoid overhyping them. The bad way is what Lewontin was talking about above.