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How Dad's Stresses Get Passed Along To Offspring (scientificamerican.com)
An anonymous reader quotes a report from Scientific American: A stressed-out and traumatized father can leave scars in his children. New research suggests this happens because sperm "learn" paternal experiences via a mysterious mode of intercellular communication in which small blebs break off one cell and fuse with another. Carrying proteins, lipids and nucleic acids, these particles ejected from a cell act like a postal system that extends to all parts of the body, releasing little packages known as extracellular vesicles. Their contents seem carefully chosen. "The cargo inside the vesicle determines not just where it came from but where it's going and what it's doing when it gets there," says Tracy Bale, a neurobiologist at the University of Maryland School of Medicine. To probe the inheritance of such changes at the cellular level, Bale and co-workers performed a series of mouse experiments.
In one set of experiments [Jennifer Chan, a former PhD student that was part of the study] stressed a group of male mice, let them mate and looked at stress responses in the pups. The clincher was a set of in vitro fertilization -- like experiments in which she collected sperm from a male mouse that had never experienced induced stress. Half his sperm went into a lab dish with vesicles previously exposed to stress hormones. The other half was cultured with vesicles that had no contact with stress hormones. Chan injected sperm cells from each batch into eggs from a non-stressed female, then implanted the fertilized eggs -- zygotes -- into the same foster mom. The pups from non-stressed zygotes developed normally. Pups from stress-exposed zygotes, however, showed the same abnormal stress response as those whose dads had experienced stress before mating. That showed extracellular vesicles act as the conduit for transmitting paternal stress signals to the offspring, Chan says.
In one set of experiments [Jennifer Chan, a former PhD student that was part of the study] stressed a group of male mice, let them mate and looked at stress responses in the pups. The clincher was a set of in vitro fertilization -- like experiments in which she collected sperm from a male mouse that had never experienced induced stress. Half his sperm went into a lab dish with vesicles previously exposed to stress hormones. The other half was cultured with vesicles that had no contact with stress hormones. Chan injected sperm cells from each batch into eggs from a non-stressed female, then implanted the fertilized eggs -- zygotes -- into the same foster mom. The pups from non-stressed zygotes developed normally. Pups from stress-exposed zygotes, however, showed the same abnormal stress response as those whose dads had experienced stress before mating. That showed extracellular vesicles act as the conduit for transmitting paternal stress signals to the offspring, Chan says.
Everything old is new again. Lamarck had his theory of evolution and Darwin had his, and for the longest time Darwin was thought to have cracked the code. I guess just like how Newton figured out physics on the macro scale there's more to be seen when one looks closely enough to see where the theory doesn't explain it all.
I recall seeing an interesting TED Talk from a man explaining how homosexuality was not genetic but epi-genetic. That is "epi-" meaning "above" or "beyond". Epi-genetics means that environmental factors placed upon the parents produce something very much like genetics on the child, as in inherent to their "code" or "being", that cannot be undone after the child is conceived. In this TED Talk the man used his son as an example of this in that the stress he and his wife had in their life produced a homosexual son because in prior times, and through many iterations of evolution taking place, there is a survival benefit of the clan or species in having homosexual men in times of stress. Things like war and famine might be where a "pause" in further offspring would be beneficial.
This fine article performed the experiment on mice and seemed a bit vague on the behavior they observed. If experiments like this can tell us more on human behaviors then there could be a lot on how we could improve society for the future. Since I already stepped on the landmine that there is a theory, not proven by the way but merely an educated guess by a man that seems convinced of the science, where stressed parents produce homosexual children then I feel like stepping on another will not be any worse.
There's the theory that a stressor that is thought to lower intelligence and raise tendencies to criminal behavior, that is children conceived out of marriage. Women being pregnant without the biological father around (or other male stand in) is stressed in a way that evidence shows might be epi-genetic. There's other possible reasons for this, like such stress in childhood upon the child will bring an adult that is aggressive and poorly educated and therefore likely to exhibit anti-social (or just plain criminal) behaviors. Or that women in such a situation will not have the time for breastfeeding (shown to be far healthier than formula), time for bedtime stories (shown to improve education later), or time for making a proper meal with any regularity. Children raised in a low stress environment tend to become well behaved adults.
Will reduced stress in society mean no more gays and criminals? Well, that would be an interesting theory to test. I don't know how we'd do that without getting into telling parents how to raise their children. Epi-genetics or not there's plenty of evidence on how a downward spiral in society can be broken by one generation of children raised in a healthy family structure. Lamarck may not have got it all right, but he wasn't all wrong either.
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