Out of Africa's midlife crisis
razib.substack.com
Out of Africa's midlife crisis
1–10 of 63 posts
Re: Out of Africa's midlife crisis
#2I subscribe to Razib’s substack. His writing style is a little weird and scattered, but he writes a lot about how this area of science is rapidly changing, and has good coverage of new hominid fossil discoveries.
Re: Out of Africa's midlife crisis
#3I subscribe to Razib’s substack. His writing style is a little weird and scattered, but he writes a lot about how this area of science is rapidly changing, and has good coverage of new hominid fossil discoveries.
Yep, my take was that the content of this article is brilliant but there is something annoying about the writing at the paragraph level that needs work.
Re: Out of Africa's midlife crisis
#4I thought this was an interesting article. Summarizing from my very-non-expert POV, he's dividing the world into three groups: a small number (less than 1 million) original African inhabitants; a larger number (about a billion) sub-Saharan Africans who broke off about 100,000 years ago; and then the rest-of-the-world (who went though a tight bottleneck less than 100,000 years ago) about the time they left Africa.
The surprising part is that measured genetic diversity within the small group of original Africans is greater than that of rest-of-the-world. Counter to intuition that skin tone is a strong indicator of relatedness, a Swede and an Andaman Islander probably have more common genetics than two members of different tribes who both live in the Kalahari desert in Namibia.
I'm confused though by his comments about "our species’ one-time amazing levels of genetic diversity." Overall, he seems to be espousing the idea that "diversity" is something we once had lots of, but have lost over time. Is this true? Did the the different tribes of African Bushmen start out as genetically distinct as they are today, or did they start from a common population and diverge over the last 200,000 years? Were those who left Africa always distinct from those who stayed, or did they change through selection (and interbreeding with Neanderthals and Denisovans) over time?
Re: Out of Africa's midlife crisis
#5On an extremely tangential note: I wish we would stop using the term, "Sub-Saharan." The semantic quandaries should be obvious, but it also subscribes to a curious linguistic glitch of putting the North and South into a hierarchy that only exists if you are rather incurious about the ambiguity of geographic perspective (see: the infamous "upside down" Gall-Peters projection for some mind-blowey fun). I would personally prefer something like "SOS (South-of-Sahara) Africa," or perhaps even something as provocative as "Africa Major" (riffing on Asia Minor and referring to the fact that that part of the continent is, in fact, a majority of its landmass).
Re: Out of Africa's midlife crisis
#6On an extremely tangential note: I wish we would stop using the term, "Sub-Saharan." The semantic quandaries should be obvious, but it also subscribes to a curious linguistic glitch of putting the North and South into a hierarchy that only exists if you are rather incurious about the ambiguity of geographic perspective (see: the infamous "upside down" Gall-Peters projection for some mind-blowey fun). I would personal…
Nobody in their right mind actually thinks placement towards the top of a map actually denotes some kind of hierarchy.
Re: Out of Africa's midlife crisis
#7On an extremely tangential note: I wish we would stop using the term, "Sub-Saharan." The semantic quandaries should be obvious, but it also subscribes to a curious linguistic glitch of putting the North and South into a hierarchy that only exists if you are rather incurious about the ambiguity of geographic perspective (see: the infamous "upside down" Gall-Peters projection for some mind-blowey fun). I would personal…
Nobody in their right mind actually thinks placement towards the top of a map actually denotes some kind of hierarchy.
There is no top of the map since there is no objective frame of reference in space. The axis on which the Earth spins relative to its orbit is a point of orientation but which side is the "top" is arbitrary.
Re: Out of Africa's midlife crisis
#8For 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?
Re: Out of Africa's midlife crisis
#9Earlier quoted context omitted.
Nobody in their right mind actually thinks placement towards the top of a map actually denotes some kind of hierarchy.
There is no top of the map since there is no objective frame of reference in space. The axis on which the Earth spins relative to its orbit is a point of orientation but which side is the "top" is arbitrary.
Yes, everybody knows that, and if someone asks me where Greenland is on a map, I will say "at the top" like a normal person.
Re: Out of Africa's midlife crisis
#10I thought this was an interesting article. Summarizing from my very-non-expert POV, he's dividing the world into three groups: a small number (less than 1 million) original African inhabitants; a larger number (about a billion) sub-Saharan Africans who broke off about 100,000 years ago; and then the rest-of-the-world (who went though a tight bottleneck less than 100,000 years ago) about the time they left Africa. The…
As a general rule, species start out with fairly high levels of diversity from natural processes of evolution. What happened with the out-of-Africa population is what's known as the founder effect. A small population leaves and becomes reproductively isolated. Whatever diversity can be found in their descendents is largely limited to the diversity that was present in the founding population.
One thing that should be made very clear is that ancient population structures generally don't map neatly to modern cultures or languages. It's best to treat modern terms as labels of convenience.