4 ms·

The data seems kind of mixed on that. I would guess that the variant had little selective pressure - being grouchy and tired all the time isn't enough to kill p

The data seems kind of mixed on that. I would guess that the variant had little selective pressure - being grouchy and tired all the time isn't enough to kill people or prevent them from reproducing. Here is the specific mutation in the gnomAD genome browser / variant database: https://gnomad.broadinstitute.org/variant/12-107386740-T-G?dataset=gnomad_r2_1 https://gnomad.broadinstitute.org/variant/12-107386740-T-G?d... The variant is particularly frequent in Ashkenazi Jews (which says very little about any selective effects), but it seems to be more prevalent in African-descent people than Finns, and more prevalent in South Asians than Europeans. So it doesn't seem especially common in Europeans, or even particularly related to latitude/longitude.

im3w1l 6y ago
> being grouchy and tired all the time isn't enough to kill people or prevent them from reproducing. It may not be enough by itself, but it's easy to imagine it being the last straw so to speak. An alternative explanation could be that society needs a certain percent of night owls. That there is a niche in which it's beneficial.
- ojnabieoot 6y ago
  It’s a huge mistake to go grasping for an adaptive explanation to every single mutation. The null hypothesis is that “this disorder doesn’t kill people before sexual maturity, or provide some reproductive gain” and there’s literally no evidence for anything else. You are speculating about a solution to something that isn’t actually a mystery. And as I said in another comment, the disorder this mutation causes is not normal “sleep late, wake late” night owl syndrome.
  - im3w1l 6y ago
    If the variant is prevalent then I can only see two explanation: either it is(was at some point) adaptive, or there was some kind of founder effect - where a small group of people that just happened to have it and become hugely genetically successful for other reasons.
    - ojnabieoot 6y ago
      The thing is that it isn’t that prevalent! Please look at the link I posted with the data - almost every ethnic group listed has less than 1% prevalence. The group it is most prevalent in is Ashkenazi Jews (3.4%), who have an unusual history that discouraged cross-ethnic relationships for millennia, and who are prone to many recessive genetic disorders that would have otherwise been more diluted. These mutations are not so prevalent because Ashkenazi Jews needed them to survive European persecution: they are the consequence of said persecution. There really does not have to be an adaptive explanation or an adaptive “coincidence” like you suggested with the founder effect. Please please please please look at the data.
      - im3w1l 6y ago
        That's still quite a lot of people in absolute numbers. I'm not sure I buy that so many can have it without any reason at all.
        Armisael16 6y ago
        The reason would be that there are a lot of people in general and the trait isn’t harmful enough to be weeded out. Humans are not perfectly optimized packages.
        im3w1l 6y ago
        > trait Just want to mention this mistake. We are talking about a gene variant, not a trait. Phenotype inheritance is much more complicated than genotype inheritance.
        ojnabieoot 6y ago
        A common misconception about natural selection is that it optimizes species. It’s really more about “this has bugs but it’s good enough to cut a release branch.”
- lmilcin 6y ago
  It might be simpler explanation. Homo Sapiens evolved in Africa where there are no long winter nights and huge variations of daily cycle throughout the year. Also humans can do shit in sunlight only. Like hunt. Then we moved to a different zone where there is longer nights and then we learned to do stuff that could be useful to be done "after hours". The pressure on good nights sleep immediately after dark lessened. Actually, people had to learn to work in the dark because in central and northern Europe there isn't much sunlight in the winter. Even in daytime there is usually overcast and no direct sunlight.
lmilcin 6y ago
I don't know what kind of data. I live in Poland and I spent my young years on a farm. In the winter you barely see any sunlight. There is nothing to do outside but plenty to do inside as you take care for the animals and do other stuff that you don't have time for in the summer. I assume this has been the same for pretty much everybody in Europe for thousands of years except for the last couple of decades.
- ojnabieoot 6y ago
  The link I posted is the data you are looking for. In particular it days that the DPSD mutation is more common in Africans than in Finnish people, and more common in South Asians than Europeans. The lengths of days and nights seems to have nothing to do with the prevalence of the mutation. So these “evolutionary adaptation” explanations are a) not supported by the data and b) unnecessary to begin with!
  - lmilcin 6y ago
    I wrote "I wonder if". No need to assume this is an attempt to explain something with evolutionary pressure.
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.

im3w1l 6y ago

> being grouchy and tired all the time isn't enough to kill people or prevent them from reproducing. It may not be enough by itself, but it's easy to imagine it being the last straw so to speak. An alternative explanation could be that society needs a certain percent of night owls. That there is a niche in which it's beneficial.

ojnabieoot 6y ago
It’s a huge mistake to go grasping for an adaptive explanation to every single mutation. The null hypothesis is that “this disorder doesn’t kill people before sexual maturity, or provide some reproductive gain” and there’s literally no evidence for anything else. You are speculating about a solution to something that isn’t actually a mystery. And as I said in another comment, the disorder this mutation causes is not normal “sleep late, wake late” night owl syndrome.
- im3w1l 6y ago
  If the variant is prevalent then I can only see two explanation: either it is(was at some point) adaptive, or there was some kind of founder effect - where a small group of people that just happened to have it and become hugely genetically successful for other reasons.
  - ojnabieoot 6y ago
    The thing is that it isn’t that prevalent! Please look at the link I posted with the data - almost every ethnic group listed has less than 1% prevalence. The group it is most prevalent in is Ashkenazi Jews (3.4%), who have an unusual history that discouraged cross-ethnic relationships for millennia, and who are prone to many recessive genetic disorders that would have otherwise been more diluted. These mutations are not so prevalent because Ashkenazi Jews needed them to survive European persecution: they are the consequence of said persecution. There really does not have to be an adaptive explanation or an adaptive “coincidence” like you suggested with the founder effect. Please please please please look at the data.
    - im3w1l 6y ago
      That's still quite a lot of people in absolute numbers. I'm not sure I buy that so many can have it without any reason at all.
      - Armisael16 6y ago
        The reason would be that there are a lot of people in general and the trait isn’t harmful enough to be weeded out. Humans are not perfectly optimized packages.
        im3w1l 6y ago
        > trait Just want to mention this mistake. We are talking about a gene variant, not a trait. Phenotype inheritance is much more complicated than genotype inheritance.
      - ojnabieoot 6y ago
        A common misconception about natural selection is that it optimizes species. It’s really more about “this has bugs but it’s good enough to cut a release branch.”
lmilcin 6y ago
It might be simpler explanation. Homo Sapiens evolved in Africa where there are no long winter nights and huge variations of daily cycle throughout the year. Also humans can do shit in sunlight only. Like hunt. Then we moved to a different zone where there is longer nights and then we learned to do stuff that could be useful to be done "after hours". The pressure on good nights sleep immediately after dark lessened. Actually, people had to learn to work in the dark because in central and northern Europe there isn't much sunlight in the winter. Even in daytime there is usually overcast and no direct sunlight.

lmilcin 6y ago

I don't know what kind of data. I live in Poland and I spent my young years on a farm. In the winter you barely see any sunlight. There is nothing to do outside but plenty to do inside as you take care for the animals and do other stuff that you don't have time for in the summer. I assume this has been the same for pretty much everybody in Europe for thousands of years except for the last couple of decades.

ojnabieoot 6y ago
The link I posted is the data you are looking for. In particular it days that the DPSD mutation is more common in Africans than in Finnish people, and more common in South Asians than Europeans. The lengths of days and nights seems to have nothing to do with the prevalence of the mutation. So these “evolutionary adaptation” explanations are a) not supported by the data and b) unnecessary to begin with!
- lmilcin 6y ago
  I wrote "I wonder if". No need to assume this is an attempt to explain something with evolutionary pressure.

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.