This longish article is admirably cautious but offers many examples to work with:
One of the outstanding questions in the field is why epigenetic inheritance only lasts for a handful of generations and then stops, said Eric Greer, an epigeneticist at Harvard Medical School and Boston Children’s Hospital who studies the epigenetic inheritance of longevity and fertility in C. elegans. It appears to be a regulated process, in part because the effect persists at the same magnitude from one generation to the next, and then abruptly disappears. Moreover, in a paper published in Cell in 2016, Rechavi and colleagues described dedicated cell machinery and specific genes that control the duration of the epigenetically inherited response. “So it’s an evolved mechanism that likely serves many important functions,” Rechavi said.
But what exactly is adaptive about it? If the response is adaptive, why not hardwire it into the genome, where it could be permanently and reliably inherited?
Viviane Callier, “Inherited Learning? It Happens, but How Is Uncertain” at Quanta
Why do the epigenetic changes last only a few generations? Hmmm. Well, if life, in general, exists by design and not by chance, many adaptations may only be intended to last a few generations. Environments constantly change, after all, and a requirement that all patterns be locked in could be a road to extinction.
See also: Genetic Literacy Project: Most Epigenetic Changes Not Passed On To Offspring
and
Epigenetic change: Lamarck, wake up, you’re wanted in the conference room!
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