A survey article in Nature discusses the growth of interest in epigenetics (non-Darwinian inheritance of traits), noting that one barrier to its acceptance is that we don’t know how the mechanism actually works:
Male rats fed a high-fat diet, for example, beget daughters with abnormal DNA methylation in the pancreas. Male mice fed a low-protein diet have offspring with altered liver expression of cholesterol genes3. And male mice with pre-diabetes have abnormal sperm methylation, and pass on an increased risk of diabetes to the next two generations.
“We and many other people have now shown these paternal effects,” says Rando, who led the low-protein study. “And we’re all having a hell of a time figuring out how they work.”
Some teams hope to be getting closer. In one study on inherited fear in mice,
Dias and Ressler do not claim to understand exactly what is going on, but they do have a working hypothesis. Somehow, the information about the frightening smell gets into a mouse’s testes and results in lower methylation of the Olfr151 gene in sperm DNA. The researchers even ran experiments using in vitro fertilization to make sure that the father was not in some way passing on a fear of acetophenone through interactions with the mother. The epigenetic tweak in the sperm is perpetuated in the offspring’s DNA, leading to increased expression of the receptor in the animals’ noses and, ultimately, enhanced sensitivity to the smell.
But much more work remains. What’s really significant is, “Although many are scratching their heads over the holes in the proposed mechanism, few are suggesting that the underlying phenomenon is a fairy tale.”
Lamarck was right, apparently, but he didn’t have a pressure group behind him.
See also: Epigenetics: Possible reason Mice are so timorous
Epigenetics: A look at a pioneer and his field
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