Yet another journalist seems to have fallen for the epigenetics mavens: those revisionists who think that a form of Lamarckian inheritance can be important in evolution. These people claim that the environment itself directly changes the DNA, not by altering the sequences of bases, but by somehow placing methyl groups on some of the DNA bases (“methylation”). Such changes can be passed on to the next generation, and so the revisionists (aka “careerists”) argue that the inherited epigenetic changes could be subject to natural selection, leading to a form of evolutionary change that is, roughly, the inheritance of acquired characters.
In a new piece on Big Think,”How about a new theory of evolution with less natural selection?“, journalist Robby Berman pushes this idea, noting that it was a big part of the recent Royal Society conference on “New Trends in Evolutionary Biology: Biological, Philosophical, and Social Science Perspectives.” (I discussed the problems with this conference’s proposals here.)
Among the problems with seeing environmentally acquired epigenetic changes as an important cause of adaptation—problems that I’ve discussed ad nauseam—are the following:
- Virtually all epigenetic markers are wiped clean as the DNA goes through gamete formation, and wiped clean within a few generations after they arise. Such changes cannot serve as a basis for permanent adaptation, which is what the epigenetics mavens claim.
- There is little evidence for environmentally induced epigenetic changes in vertebrates, an observation relevant to the article under discussion.
- When geneticists are able to map adaptive changes in the genome using crosses and DNA sequencing, they invariably show changes in the base sequence of DNA, not to methylation of those bases.
- If some DNA base sequences are more liable to environmentally-induced methylation themselves, and those methylated changes are adaptive, then the susceptible DNA base sequences will increase in frequency. But this is straight natural selection on the DNA, not a drastic revision of how natural selection works.
- Some methylation changes are coded by the DNA: DNA bases that say to the genome “put methyl groups on bases X, Y, and Z”, and that form of methylation can be adaptive, for example in mediating parent-offspring conflict. But this form of evolution is not not induced by the environment; rather, it’s coded in the genome itself, and evolves via conventional natural selection (i.e., mutations that change the DNA sequence in an adaptive way become more frequent.)
We still have not a single instance of adaptive evolutionary change arising via environmental, epigenetic modification of the DNA, and yet people are still talking as if it’s a serious difficulty for modern evolutionary theory. Well, when you show me a dozen cases of it, then we’ll talk. In the meantime, the rest is simply unfounded speculations issued by ambitious evolutionists.
And such speculation is rife in Berman’s Big Think piece. (I’m starting to think that not a lot of thought goes into some of the Big Thinks.) First of all, though admitting there are detractors, Berman accepts epigenetics as a major challenge to evolutionary theory. It isn’t—at least until we get some data. Second, he raises the idea that human agriculture, of all things, is a genetic adaptation that arose through environmental modification of the DNA. Get a load of this:
Still, epigeneticists hope the field can help explain evolutionary changes that don’t seem to be accounted for by modern evolutionary synthesis.
For example, speaking at the Royal Society was Melinda Zeder, who talked about the way in which modern synthesis fails to provide a reason for mankind’s turning to agriculture 10,00 years ago and its ensuing evolutionary impact. Growing crops may have taken years, so there could not have been a short-term evolutionary benefit to it. As Zeder told Quanta, “You don’t get the immediate gratification of grabbing some food and putting it in your mouth.” It’s also been theorized that a climate shift caused agriculture to bloom, but there’s no evidence of such a shift.
Zeder suggests we take a different view of humans at the time as creative individuals who deliberately decided to change their environment by farming, pushing human evolution in that new direction. This process is called “niche construction,” and it’s more than just a human behavior; think beavers and their dams.
First of all, Berman doesn’t seem to realize that “niche construction”—the idea that organisms, by their behavior, can change their environment in a way that affects their future evolution—is not the same thing as epigenetics. Niche construction involves perfectly normal adaptive changes in the DNA that are not induced by the environment, but simply adapt the organism to a novel environment it encounters due to a change in behavior or physiology (and those changes themselves, like leaving the water for the land, could have resulted from conventional natural selection).
Berman has no idea what he’s talking about here.
But that aside, can epigenetics explain agriculture? Why do we assume, as both Zeder and Berman seem to have done, that growing crops is coded in the human genome? It seems much more likely that it’s a cultural adaptation: something useful figured out by our ancestors and then passed on by learning. If humans were raised in an environment without having any access to such learning, would their genes tell these naive people to put seeds into the ground? I doubt it! There’s no need to explain agriculture as a genetic change, much less a Lamarckian, epigenetic change.
Nor do we have to invoke a climate shift as the impetus for agriculture. All we need to happen is for someone to discard seeds and see that useful plants grew from them. Or to have someone pick some useful plants and realize that they could be propagated from shoots or seeds.
Finally, it often takes less than a year to grow a crop, so why does Berman repeat the idea that “growing crops may have taken years.” It may have taken years to refine agriculture, but not to get it started.
This is what we call abysmal scientific journalism. But does Berman know any science? His Big Think bio describes him like this:
I’m a writer, musician, and father living in the very upper Midwest with my wife, two daughters, three cats, and countless questions. I’m especially interested in animal rights, creativity, politics, the nature of things and time, and in making a worthwhile contribution. You can follow me @everyrobby.
Well, good about the cats, but this doesn’t show much training in science. Now I don’t often go after people for lacking formal sceintific credentials, but when someone fails as spectacularly as Berman, one might pin the blame on his lack of scientific training. At any rate, the Big Think has created a Big Stink, making naive readers think that epigenetics is not only a novel and important source of evolutionary change, but one responsible for a cultural shift—agriculture—that might not even be a genetic adaptation.
Woe is me! Or, as the landsman says, “Oy vey!”