I’ve discussed at great length the lack of evidence that the environment can change the DNA in a way that is both inherited through successive generations and can also be adaptive: the view that there is a new “epigenetic” form of Lamarckian inheritance of acquired characteristics. Go here to see a panoply of my pieces on this topic. The pervasive and loud claims that there is a new and non-Darwinian form of evolution afoot stand in stark contrast to the lack of evidence supporting those claims.
And it’s even worse than I thought. At the post below at the Wiring the Brain site, Kevin Mitchell, a neuroscience researcher in Dublin, takes a hard look at the claims in humans and other species—and finds them severely wanting.
Just go to the links on his post to see his earlier writings taking apart the very weak evidence for transgenerational inheritance of acquired epigenetic DNA changes, but I’ll provide some links in an excerpt:
I recently wrote a blogpost examining the supposed evidence for transgenerational epigenetic inheritance (TGEI) in humans. This focused specifically on a set of studies commonly cited as convincingly demonstrating the phenomenon whereby the experiences of one generation can have effects that are transmitted, through non-genetic means, to their offspring, and, more importantly, even to their grandchildren. Having examined what I considered to be the most prominent papers making these claims, I concluded that they do not in fact provide any evidence supporting that idea, as they are riddled with fatal methodological flaws.
While the scope of that piece was limited to studies in humans, I have also previously considered animal studies making similar claims, which suffer from similar methodological flaws (here and here). My overall conclusion is that there is effectively no evidence for TGEI in humans (contrary to widespread belief) and very little in mammals more generally (with one very specific exception).
Jill Escher (@JillEscher), who is an autism advocate and funder of autism research, recently posted a riposte, arguing that I was far too sweeping in my dismissal of TGEI in mammals, and listing 49 studies that, in her opinion, collectively represent very strong evidence for this phenomenon.
So, have I been unfair in my assessment of the field? Could it possibly be justified to dismiss such a large number of studies? What is the right level of skepticism to bring to bear here? For that matter, what level of skepticism of novel ideas should scientists have generally?
It turns out that Mitchell hasn’t been unfair in his assessment. The 49 studies cited by Escher are riddled with flaws, including un-kosher statistical analysis (p-hacking, failure to correct probability values for multiple comparisons, incorrect analyses). Further, epigenetics research has stalled at the point where mechanism is neglected: researchers using flawed methodology just report the phenomenon over and over again, with little progress being made. He also claims that there are no plausible mechanisms for this form of environmental stimulus to produce heritable behavior that persists several generations down the line, and that the possibility of epigenetic behavior being transmitted to future generations doesn’t solve any long-standing puzzles. The buzz about epigenetics is, I think, just one of those “Darwin was wrong” ideas that persists because of its revolutionary character, despite the lack of any supporting evidence.
Ultimately, there is nothing where we can say: “We know that X happens, but we don’t know how. Maybe TGEI is a mechanism that can mediate X.” Instead, the introduction to these papers usually reads like this: “We know that TGEI [trans-generational epigenetic inheritance] can happen in X. [Narrator: we don’t know that]. Maybe it also happens in Y”.
So, until someone can show me a scenario where TGEI solves a known problem, has at least a conceivable, biologically plausible mechanism, is robust enough to provide an experimental system to work out the actual mechanism, and has convincing enough evidence of existing as a phenomenon in the first place, I will keep my skepticometer dialled to 11.
Until we have strong and repeated evidence for TGEI and, for evolutionists, evidence that it’s led to any adaptive evolution in nature, the proper attitude is firm skepticism. Caveat lector.