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…and Lamarck was right.
Well, maybe. Of the two major theories of human evolution developed in the 19th century, Darwin believed in natural selection — that human traits are passed along through DNA and not through environmental factors — and Lamarck believed that parents can transmit environmentally acquired traits.
Darwin won the sweepstakes, but Lamarck may not have been entirely wrong. From ArsTechnica:
…scientists exposed male mice to six weeks of alternating stressors like 36 hours of constant light, a 15-minute exposure to fox odor, exposure to a novel object (marbles) overnight, 15 minutes of restraint in a 50 mL conical tube, multiple cage changes, white noise all night long, or saturated bedding.
Poor little guys.
Then the scientists allowed the mice to breed. Adult offspring of these chronically stressed dads had reduced hypothalamic-pituitary-adrenal stress axis reactivity; when they themselves were restrained for 15 minutes, they did not make as much corticosterone as mice sired by relaxed dads. This is relevant, and problematic, because blunted stress responses in humans are associated with neuropsychiatric disorders like depression, schizophrenia, and autism.
In other words, dads better learn to relax a bit:
The researchers found that stressed dads have increased levels of nine microRNAs in their sperm. The scientists obviously hypothesized that these miRNAs were responsible for the reduced corticosterone response in the kids, and they set out to test it by injecting a similar cocktail of RNA into single-cell mouse zygotes. After these zygotes divided into two cells, one of the cells was allowed to develop into a full-grown mouse and the other was taken for genetic analysis. The mice that got these miRNAs looked exactly the same as those born to the stressed dads; as adults, they had the same blunted stress response and transcriptional changes in their brains. So the miRNAs are responsible for transmitting this effect.
On the other hand, let me ask the dads out there: seeing the world the way it is these days, isn’t being totally stressed out the most rational way to be?