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Researcher: The question is not whether epigenetic learning is inherited but how

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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


Epigenetic change: Lamarck, wake up, you’re wanted in the conference room!

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I'm not sure why this is even a controversial topic. Every system stabilized by feedback, has to match the speed of the changes with the speed of the feedback. It's all about managing "poles" in the complex frequency plane, as every electrical engineer learns in "Control Theory". So some epigenetic systems last 4 generations, some 4 years, and some 4 days. From the first 100 years observing the "Flynn Effect" in IQ scores, it looks to be a 5 or 6 generation feedback. It takes perhaps 100-200 years to go from an "interstadial" warm period back into an Ice Age. One would imagine that 4-6 generations of epigenetics would help humans survive the transition. And of course, we have Moses telling us that the sins of the father persist 3 to 4 generations. So that seems to be the canonical time period for epigenetic changes. Robert Sheldon

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