Grandma’s Experiences Leave a Mark on Your Genes, says this Discover article, making no mention of grandpas, and including this rather unfortunate sentence:
“Like silt deposited on the cogs of a finely tuned machine after the seawater of a tsunami recedes, our experiences, and those of our forebears, are never gone, even if they have been forgotten.”
Silt aside, if you’re interested in genetics and epigenetics, which I am on the periphery but haven’t had much time to refresh myself, it’s a fairly in-depth look at the premise that no one is free who has a thousand ancestors (I stole that phrase from Louisa May Alcott’s Emily books). In other words, the very genes you’re sitting on right now were shaped and shifted by the life experiences of your mom, grandma, great-grandma, and so forth.
Or just read it for the odd turns of phrase peppered throughout, such as this slightly sinister one:
“Of course, it is generally not possible to sample the brains of living people.”