There’s a new study out about epigenetics and it’s just more proof that Lamarck may not have been as completely batty as we all learned in school.
It does still appear to be true that Darwinian natural selection is the way evolution occurs, but it’s also become pretty clear that the experiences of the parent do impact the genetic expressions of the child. This means that the parents’ experiences thereby impact their child’s survival and thus whether or not their genes continue to be passed on. Thus the lifetime experiences of the parent do impact the Darwinian fitness of the child.
So while Lamarck might not have been right that giraffes stretching their necks to reach higher food passes the stretched neck on to their offspring and so on, he was right in this different sense. For example, it now seems that a giraffe who survives a period of starvation long enough to pass on their genes, might also then pass on epigenetic factors altering the expression of their offspring’s code, making them more likely to also survive starvation.
What’s more, the science suggests this is not some weird giraffe specific phenomenon (OK, “not some weird worm-specific phenomenon” as the author of the study footnoted put it). Instead, there seems to be solid evidence this kind of effect happens throughout all fauna (and, if I had to guess, probably all flora too). That is to say if your parents experienced extreme circumstances for long enough, they may be able to pass down epigenic factors to you that then mimic their responses to those experiences.
Of course, at the end of the day, the fact that genes can respond to epigenetic factors is encoded by…genes. So in some sense, even the epigenetic influence is coded for. But it’s still not the neat and tidy picture we have of how mutation (and mutation alone) impacts survival of the fittest.
To me, this makes a great deal of sense. Both of my parents were children of survivors of WW2. On my mother’s side, her parents lived through the Blitz (and she herself spent her first 3 years of life ducking in and out of bomb shelters). On my father’s side, his parents escaped the holocaust (while most of their families did not).
In the psychological sense, we have known for a long time this kind of trauma is passed down. It impacts behavior in such a way that it changes how children are raised and thus how those children raise their children. The most concrete and possibly well-known example of this being how children who witness domestic violence are that much more likely to perpetrate it as adults.
But these new studies about epigenetics suggest there is also a genetic component to such intergenerational trauma. This shouldn’t be surprising really – even in the molecular biology of genetics and genomics, hindsight is 20/20. After all, societal conditions rarely last only a single generation. What we consider to be “Pogroms,” for example, were a relatively regular occurrence for 130 years. This is an insignificant amount of time for traditional Darwinian evolution to occur, but such events still have a (massive) impact on survival. So what better way to increase the chances of your offspring’s survival than a mechanism for altering genetic expression in the very next generation (and the next)? This is a great alternative to waiting 100 generations before your offspring improve their ability to (for example) wake up when someone bangs on the door in the middle of the night.
So maybe now the evidence is mounting, it’s time for the implications for therapy and treatment of the children of survivors to trickle down. The fact that your parents’ (or grandparents!) PTSD seems to have been passed on to you may simply not be treatable by “talking it through” – it could be encoded in you. And, if it is, it could require different treatments than those we have embraced for the last 30-40 years.