3 ms·

For me, it's easier to understand these ideas by adopting a "lumper" mentality to human history. IE, Neanderthals, Denisovans, late Erectus & other archaics wer

For me, it's easier to understand these ideas by adopting a "lumper" mentality to human history. IE, Neanderthals, Denisovans, late Erectus & other archaics were just populations of humans. Sections on a large map of human diversity. On another section were, for example, that small subpopulation accounting for most modern human genetics. Near that little section were other subpopulations that even a "splitter" would call Sapiens. Just because they're Sapiens and we're Sapiens doesn't mean that they left more genetic legacy than Neanderthal subpopulations. I do have some questions though... "If you don’t have Sub-Saharan African ancestry, all of your ancestry (aside from your differential rates of Neanderthal/Denisovan ancestry) goes back to the same 1,000-10,000 humans that split off from other Africans." No introgression with other Sapien populations? We know that Sapiens existed outside of Sub-Saharan Africa long before that bottleneck. Are all additions to that genetic stock from other species? Also, what's the relationship between genetically isolated and genetically diverse? Most of our ancestors went through single a bottleneck 60kya-120kya, with non africans going through at least one more. Theirs did not go through that bottleneck or a seperate one. Coincidence, or is it part of the story somehow?

valarauko 5y ago
> No introgression with other Sapien populations? Perhaps indirectly. As he addresses later in the text, it's possible that Denisovans in South East Asia encountered Homo erectus and interbred with them. The Denisovans appear to have more population structure as compared to Neanderthals, and introgression from H. erectus might explain some of it. Considering that South East Asia and Papua New Guinea has the highest Denisovan introgression in modern humans, it's possible that some of that H. erectus ancestry ended up in those of us from East of the Indus. For what it's worth, I have seen other studies pop up from time to time that claim to have found introgression from some unknown ghost sapien population, but these outliers usually go away by tweaking the parameters.
- dalbasal 5y ago
  Interesting. What I meant though was introgression with closer groups. IE there clearly were surviving populations that didn't go through the major sapien funnels. Their descendants are in the "very diverse" group. Obviously there was, is and will be "introgression" with them. Were there other such groups, in or out of sub-saharan africa... whos genes we carry?
  - valarauko 5y ago
    I'm not sure what you mean by the other closer groups. My understanding of the field is that when anatomically modern humans expanded out of Africa for the first time 60Kya, they encountered Neanderthals and eventually Denisovans. What other "closer" group was out there for them to encounter? The other anatomically modern humans were all in Africa, and it looks like there's been no interbreeding with them for at least 100K years. There has been a small introgression back into Africa by non-Africans within the last few thousand years, but that's a separate issue.
    - dalbasal 5y ago
      Other Sapiens. People whos descendants would have been group 3, if a descendant population had survived to modern times. 90% of the DNA for groups 2 & 3 comes from those 1000-10,000 individuals. A small smattering from neanderthals denisovans and ghosts. What's the rest? There were anatomically modern humans outside of sub-saharan africa at some point. They just don't have descendants. But, my question applies either way. What matters is that they descend from groups outside of the funnel group, not where they lived.
      - valarauko 5y ago
        > 90% of the DNA for groups 2 & 3 comes from those 1000-10,000 individuals. A small smattering from neanderthals denisovans and ghosts. What's the rest? That's not my understanding of the text. Other than the 2-5% Neanderthal & Denisovan contributions, the rest of our (ie, for non-Africans) ancestry arises entirely from this single group of 1-10k, not 90%. Perhaps you're confusing it with this statement? > ... only 1,000-10,000 lucky humans made it through the impossibly narrow neck. Our best (always provisional) models suggest they dwindled from an earlier population maybe 10 times bigger. So this round of cuts diminished the breeding pool by 90%.
davisYC 5y ago
i talk about introgression in this post https://razib.substack.com/p/here-be-humans https://razib.substack.com/p/here-be-humans the piece was not exhaustive and meant to be an intro
- dalbasal 5y ago
  Cheers. These blogs are a treat.
- throwaway894345 5y ago
  Dang, you created this account back in 2015 and your first comment is from 1 hour ago.
  - davisYC 5y ago
    yeah. no idea why it's even called 'davisYC' aside from the fact i lived in davis then -razib
    - throwaway894345 5y ago
      I followed you on Twitter for several years and also heard your interview on the New Liberals podcast. Would love to see you around here more often as well.

valarauko 5y ago

> No introgression with other Sapien populations? Perhaps indirectly. As he addresses later in the text, it's possible that Denisovans in South East Asia encountered Homo erectus and interbred with them. The Denisovans appear to have more population structure as compared to Neanderthals, and introgression from H. erectus might explain some of it. Considering that South East Asia and Papua New Guinea has the highest Denisovan introgression in modern humans, it's possible that some of that H. erectus ancestry ended up in those of us from East of the Indus. For what it's worth, I have seen other studies pop up from time to time that claim to have found introgression from some unknown ghost sapien population, but these outliers usually go away by tweaking the parameters.

dalbasal 5y ago
Interesting. What I meant though was introgression with closer groups. IE there clearly were surviving populations that didn't go through the major sapien funnels. Their descendants are in the "very diverse" group. Obviously there was, is and will be "introgression" with them. Were there other such groups, in or out of sub-saharan africa... whos genes we carry?
- valarauko 5y ago
  I'm not sure what you mean by the other closer groups. My understanding of the field is that when anatomically modern humans expanded out of Africa for the first time 60Kya, they encountered Neanderthals and eventually Denisovans. What other "closer" group was out there for them to encounter? The other anatomically modern humans were all in Africa, and it looks like there's been no interbreeding with them for at least 100K years. There has been a small introgression back into Africa by non-Africans within the last few thousand years, but that's a separate issue.
  - dalbasal 5y ago
    Other Sapiens. People whos descendants would have been group 3, if a descendant population had survived to modern times. 90% of the DNA for groups 2 & 3 comes from those 1000-10,000 individuals. A small smattering from neanderthals denisovans and ghosts. What's the rest? There were anatomically modern humans outside of sub-saharan africa at some point. They just don't have descendants. But, my question applies either way. What matters is that they descend from groups outside of the funnel group, not where they lived.
    - valarauko 5y ago
      > 90% of the DNA for groups 2 & 3 comes from those 1000-10,000 individuals. A small smattering from neanderthals denisovans and ghosts. What's the rest? That's not my understanding of the text. Other than the 2-5% Neanderthal & Denisovan contributions, the rest of our (ie, for non-Africans) ancestry arises entirely from this single group of 1-10k, not 90%. Perhaps you're confusing it with this statement? > ... only 1,000-10,000 lucky humans made it through the impossibly narrow neck. Our best (always provisional) models suggest they dwindled from an earlier population maybe 10 times bigger. So this round of cuts diminished the breeding pool by 90%.

davisYC 5y ago

i talk about introgression in this post https://razib.substack.com/p/here-be-humans https://razib.substack.com/p/here-be-humans the piece was not exhaustive and meant to be an intro

dalbasal 5y ago
Cheers. These blogs are a treat.
throwaway894345 5y ago
Dang, you created this account back in 2015 and your first comment is from 1 hour ago.
- davisYC 5y ago
  yeah. no idea why it's even called 'davisYC' aside from the fact i lived in davis then -razib
  - throwaway894345 5y ago
    I followed you on Twitter for several years and also heard your interview on the New Liberals podcast. Would love to see you around here more often as well.