This shouldn't be too surprising. It is well known that what a mother ingests during pregnancy can affect development, so it makes sense that stress-related hormones could do the same.
This article is specifically not just about "during pregnancy" though. Quote:
"It suggested that trauma might have affected the mothers' eggs decades before her children were conceived, while she was herself a child."
"They gave a male mouse a mild electric shock as it smelled a cherry blossom scent, stimulating a fear response to the odor. The response was accompanied by epigenetic changes in its brain and sperm. Intriguingly, the male offspring of the shocked mice demonstrated a similar fear of cherry blossoms—as well as epigenetic changes in their brain and sperm—without being exposed to the shock. These effects were passed down for two generations. In other words, the lesson the grandfather mouse learned, that the cherry blossom scent means danger, was transmitted to its son and grandson."
Yeah, I have to confess that I didn't get that far. I pretty much stopped here:
"The effect was most prominent in babies whose mothers had been in their third trimester on that fateful day."
At which point I thought, "OK, that's not surprising", wrote my comment, and went on to other things.
Frankly, I am extremely skeptical of the mouse results. I would be really surprised if this turned out to be reproducible. It's Lamarckian evolution, which has been long-discredited, which makes this an extraordinary claim which requires extraordinary evidence. By what possible mechanism could memory of a smell be recorded in a gamete's DNA?
That’s totally different. What’s unique here is the epigenetic mechanism of the effect. The effects are fixed at conception when recombination occurs and have nothing to do with development in the womb.
Edit: it’s also worth noting that epigenetic effects can span generations[1], something that a purely environmental effect could not.
Well, that's not quite true. The first half of the article is about effects of stress during gestation.
"The effect was most prominent in babies whose mothers had been in their third trimester on that fateful day."
> epigenetic effects can span generations[1], something that a purely environmental effect could not
Why not? It seems to me the only way you could rule out environmental effects is if there are no aspects of the environment that are constant across generations, otherwise those constant aspects of the environment would necessarily effect multiple generations.
> Well, that's not quite true. The first half of the article is about effects of stress during gestation.
Quoting from the article, the researcher starts looking due to the presumed effects of stress during gestation:
> Finding low cortisol in the 9/11 babies back in 2002 had told us that we'd been thinking about some things all wrong. We'd assumed all along that trauma was behaviorally transmitted: Joseph's problems seemed to result from the stressful, bereaved atmosphere in his childhood home. But now it looked like the uterine environment also played a role. So did the sex of the traumatized parent.
However, ultimately, the key discovery of the article is actually about epigenetic causes and not due to the (current) mother’s uterine environment:
> In 2020 we reported lower levels of FKBP5 methylation in the adult children whose mothers—and not fathers—were exposed to the Holocaust during childhood. This effect was independent of whether the mother had PTSD or not. It suggested that trauma might have affected the mothers' eggs decades before her children were conceived, while she was herself a child.
I agree with you that you can’t rule out environmental effects without a trial that controls for the effects of the current environment. However, the featured article is really about the hereditary effects, ostensibly epigenetic in nature, rather than nonhereditary.
