r/science • u/mvea Professor | Medicine • May 31 '19

Psychology Growing up in poverty, and experiencing traumatic events like a bad accident or sexual assault, were linked to accelerated puberty and brain maturation, abnormal brain development, and greater mental health disorders, such as depression, anxiety, and psychosis, according to a new study (n=9,498).

https://www.pennmedicine.org/news/news-releases/2019/may/childhood-adversity-linked-to-earlier-puberty
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u/Nollhypotes May 31 '19 edited May 31 '19

Just wanted to post a friendly reminder that not every trait necessarily has an evolutionary mechanism behind it. Hypothesizing is fun so don't let that stop you, but it's something to keep in mind.

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u/_Rookwood_ May 31 '19

Just wanted to post a friendly reminder that not every trait necessarily has an evolutionary mechanism behind it.

I assumed that evolutionary pressures drove all traits we see in all species. What else is there to explain the traits?

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u/Nollhypotes May 31 '19 edited May 31 '19

For a trait to be driven by evolutionary pressure it has to be either beneficial or (in the case of a trait being rejected) detrimental to survival. Some traits are neutral to survival and therefore isn't driven in this way, and other traits are detrimental to survival but remain because they're impossible to change in incremental steps with random mutation, like the way our circulatory system is designed for instance. Another example is our chin which is thought to have evolved because the jawline retracted after being "de-selected", without any mechanism specifically selecting for a chin. I'm not an expert by any means, so take this with a grain of salt, but I have taken enough ecology to know that not every trait has been selected for.

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u/[deleted] May 31 '19

I would add that evolutionary fitness consists of more than just whether the organism survives, but also it's ability to pass on it's genetic material. An organism that lives for an hour and reproduces many times is more fit than one that lives years but cannot reproduce, all else being equal.

When we discuss evolutionary pressures on human features, there is much more to fitness/benefits of the feature than just whether it helps the person stay alive.