3 ms·

I'm sceptical to how much evolutionary pressure we can see evidence of going back just 100 000 years or so (at the point when we became truly social creatures,

by e12e 6y ago

I'm sceptical to how much evolutionary pressure we can see evidence of going back just 100 000 years or so (at the point when we became truly social creatures, I think culture, passing on knowledge, technology and ideas became much more dominant for survival/procreation than mere genetics). That said, I think the theory that you need someone awake to ward of nocturnal predators (be they human/homid or animal) has some merit. Being eaten beforepuberty does tend to cut a genetic line short. Ed: a counter example of "modern" evolutionary pressure would be sicle anemia/malaria. A "technological" fix would be mosquito nets, relocation to a part of the world without malaria, etc. Or eating koka/coffee to stay alert on late watch.

ojnabieoot 6y ago
My favorite example of a (real) recent selective pressure is lactose tolerance, which is well-correlated with ancestry in regions that a) are prone to vitamin D deficiency (Northern Europe especially) and b) regions that have cows or sheep, regardless of sunlight. So in particular most of Africa is lactose-intolerant, but many pre-modern West African groups were pastoral herders and can digest lactose. It is a bit of a mystery how this happened: other lactose-intolerant groups still used milk to make yogurt and cheese with much less lactose, and it’s not clear why there would have been pressure for adults to drink raw milk - perhaps a water-borne disease caused a bottleneck? See epidemiology here: https://en.wikipedia.org/wiki/Lactose_intolerance https://en.wikipedia.org/wiki/Lactose_intolerance
Aromasin 6y ago
There's a good book on the topic called "Why We Sleep" by Matthew Walker, a professor of neuroscience and psychology at Berkley. In it, it discusses how teens are biologically designed stay up much later than their parents would, with the theory that this is when they would have a chance to socialise and mate without the watchful eye of parents. Not only that, it reduces the time that a tribe would be open to attack or prededation - if everyone slept at the same time, there would be an 8 hour window of the day where humans would be incredibly vunerable. Presumably it would be favourable to have a few adults in the tribe to have a similar night-owl streak, to keep the tribe secure throughout the night. The book really pushes the narative that making kids, and especially young teens wake up so early just to fit into an adults daily routinee is akin to child abuse, as it stunts their growth in ways - physically and mentally - that cannot be achieved by any means except through sleep deprivation.

by e12e 6y ago

ojnabieoot 6y ago

My favorite example of a (real) recent selective pressure is lactose tolerance, which is well-correlated with ancestry in regions that a) are prone to vitamin D deficiency (Northern Europe especially) and b) regions that have cows or sheep, regardless of sunlight. So in particular most of Africa is lactose-intolerant, but many pre-modern West African groups were pastoral herders and can digest lactose. It is a bit of a mystery how this happened: other lactose-intolerant groups still used milk to make yogurt and cheese with much less lactose, and it’s not clear why there would have been pressure for adults to drink raw milk - perhaps a water-borne disease caused a bottleneck? See epidemiology here: https://en.wikipedia.org/wiki/Lactose_intolerance https://en.wikipedia.org/wiki/Lactose_intolerance

Aromasin 6y ago

There's a good book on the topic called "Why We Sleep" by Matthew Walker, a professor of neuroscience and psychology at Berkley. In it, it discusses how teens are biologically designed stay up much later than their parents would, with the theory that this is when they would have a chance to socialise and mate without the watchful eye of parents. Not only that, it reduces the time that a tribe would be open to attack or prededation - if everyone slept at the same time, there would be an 8 hour window of the day where humans would be incredibly vunerable. Presumably it would be favourable to have a few adults in the tribe to have a similar night-owl streak, to keep the tribe secure throughout the night. The book really pushes the narative that making kids, and especially young teens wake up so early just to fit into an adults daily routinee is akin to child abuse, as it stunts their growth in ways - physically and mentally - that cannot be achieved by any means except through sleep deprivation.