Oldest human genomes reveal how a small group burst out of Africa
nytimes.com
nytimes.com
>"The huge gap between those ages could change our understanding about how humans spread across the world. If the ancestors of today’s non-Africans didn’t sweep across other continents until 47,000 years ago, then those older sites must have been occupied by earlier waves of humans who died off without passing down their DNA to the people now living in places like China and Australia."
But at the end gets a bit more balanced
>"He Yu, a paleogeneticist at Peking University in Beijing who was not involved in either study, said that the mystery wouldn’t be solved until scientists find DNA in some of the ancient Asian fossils. “We still need early modern human genomes from Asia to really talk about Asia stories,” Dr. Yu said."
This puzzle is still missing key elements.
Dr. Skoglund also said it would be strange for non-African ancestors to have arisen about 47,000 years ago while modern humans in Asia and Australia dated back 100,000 years. The sites in question could have been incorrectly dated, he said, or people could have reached Asia and Australia that long ago, only to die out.
see:
(2016) https://www.abc.net.au/news/science/2016-09-22/world-first-s...
(2017) https://www.nature.com/articles/nature21416
etc.
Such results are inherently noisy and subject to assumptions. The further back in history you go, the less accurate and reliable the results will be. Ancient DNA comes with its own issues and assumptions, but it helps with the accuracy of the results. Instead of trying to infer something that happened thousands of generations ago, you may now be only hundreds or even tens of generations from the split.
The clearest way forward would be sequencing Aboriginal Australian DNA from tens of thousands of years ago. Then you could get a more accurate estimate for the split between that population and other sequenced ancient populations.
The people that ended up in Australia were some of the earliest anatomically modern humans that successfully made the trip out and for some reason or the other were not really able to colonize Europe/Asia and kept venturing south until they ended up in Australia
Other later waves probably made it to the middle east and went back. Some made it a bit into Europe and some of asia. But it wasn't until relatively recent times, that we got waves that finally got a foothold in Europe/Asia and eventually outlasted other homo species that had dominated those areas for a 100,000 years.
I am not an anthropologist. I can't prove anything I wrote. I am just using my own common sense and the evidence that has so far been published.
Any people that did settle in Europe to the north during that first pass through further south some 70K years ago very likely were pushed back by the worsening conditions preceding the advance of the Last Glacial Maximum (dry very dusty air, poor vegetation .. and later ice everywhere).
Following the path of best land with least resistance led to following the tropics mostly by land, consistent year round conditions, no winters to store food for, etc.
Your comments do not apply with any force to this particular study.
It’s more likely competitive pressure forced them to expand out further because to a small group, even a small conflict with a neighboring tribe that costs them a few of their fittest members would be particularly traumatic and risky. It’s just easier and safer to migrate.
Archaic humans made it out to South East Asia over a million years ago back when the sea hadn’t even risen to form the major islands like Indonesia. Migration is in our DNA.
That's distinct from making a claim, an assertion with supporting evidence.
To make a claim, we would want evidence, and the evidence here would be a genetic isolation (lack of chronological overlap, synonymous with lack of interbreeding) of ancient Asian humans from ancient African humans. This requires sequencing a lot of ancient Asian DNA, which seems not to have happened yet. We barely have a cohesive evidence supported grasp of Neanderthal interactions in Europe, but are gradually updating to support more and more absorption by interbreeding.
https://en.wikipedia.org/wiki/Multiregional_origin_of_modern...
Instead, the article follow the Out of Africa origin, and therefore did not explain the old chineses and autralian remains. The article try to explain this by saying than it's because this lines where extincts or than the dates are wrong, but this explanations are not very convincing.
> “The primary competing scientific hypothesis is currently recent African origin of modern humans, which proposes that modern humans arose as a new species in Africa around 100-200,000 years ago, moving out of Africa around 50-60,000 years ago to replace existing human species such as Homo erectus and the Neanderthals without interbreeding.[5][6][7][8] This differs from the multiregional hypothesis in that the multiregional model predicts interbreeding with preexisting local human populations in any such migration.”
But it is a somewhat weird quote in the Wikipedia article. They’ve got the whole thing in quotes with multiple citations (so it isn’t clear which citation the quote comes from), it isn’t attributed to anybody in particular, and it doesn’t seem to be a very accurate description of what I though the consensus was, at least. (It is widely believed that humans interbred with other hominids, right?)
Thad said:
- as the time of the emergence of both theories there where no genetics evidences yet in one way or another
- the interbreeding with this two other species is still very small, (less than 5% of the actual genes). There is still no evidences for other important species like Homo erectus (or hedelbergensis, or florensis, etc.)
The truth maybe in between: a major pool of gene from Africa, but with small local parts from all over the ancient world.
The big remaining question is:
- Did sapiens and erectus had babies? And if yes, then, what was the results (Denisova or something else ?).
EDIT: also, I forgot that a lot of the steppe is forested. Surely that would make it significantly less of a barrier.
> also, I forgot that a lot of the steppe is forested. Surely that would make it significantly less of a barrier.
Also consider the ice age and how that affected the degree to which Eurasia was hospitable.
Does Zimmer know something that I do not? Or David Reich?
https://www.cell.com/cell/fulltext/S0092-8674(20)30059-3 https://www.pnas.org/doi/full/10.1073/pnas.1313787111
But having said all that, maybe the key point Zimmer is making IS a good generalization.
The ghost admixture story(s) will turn out to be much more localized, I imagine.
I guess it's to be expected that pop-sci is 10-15 years behind…
If you've encountered some then please share!
it used to be that we saw changes in ancient pottery and language and assumed that previous people had been replaced by new people with different techniques. then, in the 60s/70s it became popular that these changes didn’t mark population replacement but were more cultural spread and shift.
then genetics came around in the 90s and obliterated the cultural hypothesis and showed that in most of these cases it was largely population replacement.
there are lots of theories from the mid-20th that haven’t yet had their ‘genetics in the 90s’ moment.
I think the current consensus is a fusion of the two stances, particularly as some of the changes have appeared to be too rapid to reflect population displacement, and genetics clearly indicate genetic admixture with varying distinguishing characteristics relevant to the region and timeperiod as opposed to straight displacement.
Unsatisfying, I know, but basically any firm position on either side has equally firm arguments against it.
a lot of these admixture events show near total displacement of the y chromosome also
For one example, the idea a single "sea people" were responsible for the shift from bronze age to iron age in the eastern mediterranean is nearly universally rejected at this point. The populations of the mediterranean seem to descend at least in part from the bronze-age populations of the area. However the economic and cultural impact of the same period undeniably transfused rapidly through the region as heavily demonstrated with the archaeological record.
Even in the case of neanderthals we didn't fully displace so much as mostly displace but also admixed. Same with denisovans, cro magnons, etc. Genetic testing of cro-magnons shows modern-day descendants, and not just in the matrilineal or patrilineal line (i.e. presumably indicating either descendants of rape or partial infertility, as is presumed in the case of neanderthals).
With the spread of agriculture (seed cultivation, husbandry, plow, etc) we also see a mixture of genetic and cultural transfusion. Ditto with the horse, except much more rapidly, and horse-based technology much slower. This is partially why there's a gradient of genetic similarity across europe rather than a "european" set of genes—and with the horse technology, we have the benefit of an archeological and in certain cases textual evidence of trade between northern europe and the rest of the world.
Now, some of this is a matter of quibbling over semantics—is it displacement or is it admixture? Understandable. But the cultural diffusion in the material record is undeniable regardless of which term you pick. I'm not so sure it's worth picking a primary cause rather than accepting the inherent messiness of the archeological and genetic record where, as in the case of neanderthals, there isn't very solid evidence of infertility demonstrating firmly that the migration was mostly, if not entirely, displacement, as presumably non-hss-mixed neanderthals are extinct.
Are they? Are there any studies that confirm that hypothesis?
My understanding[0][1][2][3][4][5][6] (there are plenty more references, but I assume you get the point) is that modern human populations are incredibly similar, and not very diverse at all. In fact, all humans are more genetically similar to each other than many other species are, including chimpanzees and wheat.
[0] https://www.science.org/content/article/how-we-lost-our-dive...
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC7115999/
[2] https://www.ashg.org/wp-content/uploads/2019/09/genetic-vari...
[3] https://www.scientificamerican.com/article/humans-are-doomed...
[4] https://bigthink.com/life/humans-are-less-genetically-divers...
[5] https://www.jstor.org/stable/41466860
[6] https://www.kqed.org/quest/474/explosive-hypothesis-about-hu...
??? what is there to confirm? Why are you trying to spin an internal comparison as external? Indigenous populations tend to be more related to physically close indigenous populations than physically far apart indigenous populations. This is what I was referring to with the "genetic gradient". Comparing us to chimpanzees makes zero sense, let alone wheat, as we aren't trying to have sex with either, let alone "displace" them. I mean, hopefully not.
It's true that our diversity has lessened over time but this is "I don't see color" levels of delusion.
when modern populations are so genetically diverse.
And I provided documentation to support that assertion.
I didn't even get into the genetic evidence that variation within human population groups is greater than the variation between such groups.
That you made some sort of assumption as to the reason for my assertion, is on you and not me.
I merely pointed out that your assertion is not supported by the genetic evidence. Full stop.
Clear to whom? You? I'm sure it was. To anyone else? Not so much.
I read your words "I'm not disbelieving your source entirely, but it seems a little ridiculous to assume population displacement across all pre-history (or undocumented history if you'd prefer that term). Particularly when modern populations are so genetically diverse."
And you made the claim that "modern populations are so genetically diverse." Did someone commandeer your account or force you to write that at gunpoint?
If not, it was you who referenced genetic diversity.
Or does "modern populations are so genetically diverse" mean something other than "modern populations are so genetically diverse?"
As for my response, my apologies. Clearly I did not communicate my thoughts effectively. I will attempt to do so again.
>I was just pointing out there's a lot of genetically distinct humans and this genetic distinction follows geographic trends.
And your assertion is flat wrong. In fact, modern humans have very little genetic diversity, measured any way you'd like.
What's more, the human populations with the most genetic diversity are those native to Southern and Eastern Africa.
Populations everywhere else in the world are incredibly genetically similar to each other.
So much so that the differences within geographical population groups are greater than those between such groups.
As to my references to chimpanzees and wheat, that was just to point up that humans -- regardless of geographical population -- are not genetically diverse at all.
And that's it. Humans, regardless of geographic population, are remarkably similar in genetic make up. Humans are not, as you asserted, "so genetically diverse." Exactly the opposite.
Do you understand now? If not, I obviously need to learn to write more clearly.
This is one of the most unpleasant conversations in recent memory. Haven't you ever heard of good faith conversation? Jesus. Absolutely rank vibes.
It is racist BS.
There were modern humans in Australia 60k years ago. Europe was also colonized way before that date. And some modern humans never left Africa.
An easy example is that neanderthals, denisovans, h erectus, etc contribute via admixture to Homo Sapien Sapiens and well predate "out of africa" dates by hundreds of thousands of years. It's not a hard stretch to presume that other yet-unnamed branches of modern humans left earlier and admixed the same as the other named groups.
I don't think anyone is proposing an extant group of humans that don't have relatively recent roots in africa, though.
> Some 45,000 years ago, a tiny group of people — fewer than 1,000, all told — wandered the icy northern fringes of Europe.
Is it not possible that:
Some 45,000 years ago, a tiny group of people — fewer than 1,000, all told — wandered from sunny Australia into China, eventually reaching Africa and Europe?
It is impossible to tell the direction of travel.
You'd be able to look for and find some evidence of their ancestors in Australia and you don't. But there's plenty of it in Africa.
If we got this wrong, most of paleontology is unreliable.
When the hypothesis first appeared it was somewhat shocking to science, as the leading theory was some sort of parallel emergence of the races - but this was not grounded in the evidence being found in Africa at the time, and genetic evidence has since cemented this not as hypothesis, but well-established theory.