[HN Gopher] Oldest human genomes reveal how a small group burst ...
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Oldest human genomes reveal how a small group burst out of Africa
Author : diodorus
Score : 90 points
Date : 2024-12-16 05:41 UTC (2 days ago)
(HTM) web link (www.nytimes.com)
(TXT) w3m dump (www.nytimes.com)
| The-Old-Hacker wrote:
| https://archive.ph/WLcdD
| eddyzh wrote:
| Makes a huge claim at the start.
|
| >"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.
| jl6 wrote:
| It doesn't seem like an outlandish claim that many waves of
| humans tried and failed to colonize the world, until one
| succeeded. I would find it harder to believe that the first to
| leave Africa got it right first time.
| h0l0cube wrote:
| I think the claim is that earlier founders _did_ colonize the
| world before the final group left and also colonized the
| world. Land bridges disappeared as the last ice age came to a
| close, making later attempts more difficult
| defrost wrote:
| One question raised by a researcher in the article:
| 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.
|
| Doesn't mesh well with genetic studies from Australia that
| show a long history of relatively stable regionalism within
| Australia (with some still unresolved mixing from Denisovan
| ancestors.
|
| see:
|
| (2016) https://www.abc.net.au/news/science/2016-09-22/world-
| first-s...
|
| (2017) https://www.nature.com/articles/nature21416
|
| etc.
| jltsiren wrote:
| The actual results in papers like these (both the paper in
| question and the ones you refer to) are typically of the
| form: "We sequenced these genomes. Then we took the noisy
| data, made a lot of assumptions, and applied statistical
| magic to estimate that the populations split approximately
| X generations ago. We interpret that as Y years ago."
| Everything beyond that is interpretation, not the result.
|
| 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.
| naijaboiler wrote:
| my own theory. Depending on cyclical geography
| limitations, humans have been forever moving out of
| Africa sporadically, going way back to Neanderthals and
| possibly even before. It wasn't just one wave, it was
| multiple waves from time to time.
|
| 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.
| withinboredom wrote:
| I wonder if this migrate-and-survive is a "great filter"
| that organisms must do in order to grow. The same thing
| will likely happen to space colonists, many will go, but
| only a few will survive.
| defrost wrote:
| > 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
|
| 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.
| robwwilliams wrote:
| The dating of the fossils is quite secure. So in this
| dimension all is good. The DNA sequence is as good given
| the number of closely related individuals.
|
| Your comments do not apply with any force to this
| particular study.
| enkid wrote:
| I don't think a group of people living somewhere for
| thousands of years would be "getting it wrong." You're
| embedding an assumption that evolution has been working
| toward an end goal of getting humans to spread globally,
| which isn't how evolution works.
| jandrese wrote:
| It doesn't seem all that improbable that humans or close
| ancestors had colonized other parts of the world for
| thousands of years only to die off due to climate
| change/disease/other factors about 40,000 years ago when
| they had to start all over again. Or maybe the ancestors
| colonized it and the extinction event was Homo Sapiens out
| of Africa, although in this case you would expect more DNA
| mixing. It seems more likely that the ancestors died out
| for whatever reason and the humans moved into their
| habitats to refill that ecological niche.
| shellfishgene wrote:
| I doubt it's correct to assume groups of humans in Africa one
| day decided to 'colonize' another place and walked thousands
| of kilometers to settle down elsewhere. It's probably more
| like a slow expansion (and reduction) of the settled area,
| no?
| airstrike wrote:
| Both processes could coexist, right? I could see myself
| waking up one day and saying "what's the farthest we can
| get to? maybe there are amazing things at the end of the
| journey"
| bee_rider wrote:
| I'm not 100% clear on what the two processes are. In
| particular, early humans already were pretty mobile. So
| they'd be going from place to place, hunting as they go.
| Maybe following some migratory animals. If you got
| wanderlust, I guess you'd only make it a couple days
| before you ran out of food, so maybe some dozens of
| miles, and then you are back to doing typical human
| stuff, right?
| withinboredom wrote:
| it can also be stupid politics/religion: "your village is
| the reason for our famine, your entire village is banned
| from here. you will walk until you see the mountains and
| until you no longer see them behind you" ... next thing
| you know, you're in europe or asia.
| throwup238 wrote:
| Humans were nomadic before agriculture so they would have
| been moving all the time anyway. There would have been no
| settling down.
|
| 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.
| tetris11 wrote:
| I think they just walked to other places as and when the
| climate changed. Some adapted and stayed, others moved the
| greener pastures. This slow and climate-driven process can
| hardly be described as colonization.
| mapt wrote:
| It doesn't seem like an outlandish possibility.
|
| 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.
| kspacewalk2 wrote:
| And their failure doesn't mean they're completely absent from
| our genome.
| miniwark wrote:
| The view of the chinese researcher is in line with the
| Multiregional origin hypothesis of modern humans, where asian
| humans may partially come from asia. So his reply is not
| surprising.
|
| 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.
| bee_rider wrote:
| What's the most significant difference between the theories?
| The Wikipedia article says:
|
| > "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?)
| miniwark wrote:
| With recent genetics proofs than early human, did have
| interbreed with at last Neanderthals and Denisovans, this
| is now indeed more "true" than the "Only from Africa"
| hypothesis.
|
| 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 ?).
| PittleyDunkin wrote:
| Am I missing something? Surely Europe is the same continent as
| Asia. Why wouldn't people just walk over? It seems reasonable
| to assume that if evidence exists on one side of the continent
| that it'd imply existence on the other side, too. If anything
| you'd need a theory why they _failed_ to spread to formulate
| interesting discussion!
| hackinthebochs wrote:
| The Steppes are a natural barrier between East and West until
| the point where technology caught up to make it passable.
| PittleyDunkin wrote:
| Well we have human ancestors on both sides of that barrier,
| so clearly it's not insurmountable in absolute terms,
| either from taking the souther route or migrating with
| herds or some other thing I haven't thought about (I'm not
| sure waterways would get you the whole way, but it'd get
| you from the urals to either side). The question is why
| this would pose a barrier to some populations and not
| others.
|
| EDIT: also, I forgot that a lot of the steppe is forested.
| Surely that would make it significantly less of a barrier.
| hackinthebochs wrote:
| No terrain is insurmountable considering chance and a
| hundred thousand years. The question is how likely will
| any given group be able to pass through and flourish on
| the other side? We have many examples of isolated human
| populations on islands or across inhospitable barriers
| that it shouldn't be surprising to find isolated
| populations on either side of the Eurasian continent. Off
| the top of my head, Australian aboriginals, the
| Andamanese and New Guinea islanders are examples of
| isolated populations with essentially no gene flow
| between larger populations over 10s of thousands of
| years. Even the fact that we talk about how many
| populations ultimately left Africa in prehistory implies
| there must have been some barrier to overcome.
|
| > 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.
| anonymousDan wrote:
| What exactly do you mean by the Steppes? I thought this
| referred to a grassland region so can't see how it would
| constitute a barrier.
| verisimi wrote:
| Such fictional assumptions...
|
| > 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.
| pvg wrote:
| _Is it not possible that:_
|
| 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.
| Mountain_Skies wrote:
| That assumes all evidence is equally easy to find and has
| been equally searched for.
| pvg wrote:
| Sort of but we're not talking about apes and monkeys here,
| it's placental mammals in general. So the evidence is
| overwhelming https://en.wikipedia.org/wiki/Mammals_of_Austr
| alia#Evolution...
|
| If we got this wrong, most of paleontology is unreliable.
| pfannkuchen wrote:
| Africa is a static large site of habitation where the
| disappearance of 99% of evidence would still leave easily
| findable evidence. In GP's scenario the habitation would be
| transient. Not really comparable.
| reedf1 wrote:
| It is not really up for debate. Haplogroups provide direct
| lineage and evidence for migration.
| madaxe_again wrote:
| No. The genomes tell a pretty clear story. Should your
| hypothesis be correct, you would find haplogroups in the 45kya
| group descended from the 60kya austronesian group - but you do
| not. Rather, you find a most recent common ancestor _before_
| the 60kya group left Africa. As to why Africa - this is where
| ancestral hominids and the earliest known sapiens specimens
| have been found. While we have found cousins elsewhere, the
| evidence all points towards sapiens having emerged in Africa
| and spread elsewhere in successive waves.
|
| 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.
| Cthulhu_ wrote:
| I mean the fictional assumption is that it was a single group
| that wandered thousands of miles across continents; it was many
| generations that would settle somewhere, with subsequent
| generations migrating and spreading slowly, leaving behind
| traces like gravesites and settlements and the like; combine
| that with accurate dating and you _can_ in fact tell the
| direction of travel.
| vixen99 wrote:
| Thank you!
| dang wrote:
| We detached this comment from
| https://news.ycombinator.com/item?id=42430565 - your comment is
| just fine, there's nothing wrong with posting 'thank you'! But
| I wanted to pin the other link to the top, where real estate is
| expensive.
| InfiniteLoup wrote:
| Would any evidence that contradicts the 'Out-of-Africa' dogma
| even get considered by Western scientists?
| AndrewDucker wrote:
| Sure!
|
| If you've encountered some then please share!
| antman wrote:
| This appears to be a research and not part of a dogma and
| Africa is not part of the Western World. What your comment
| implies in terms of Science and Conspiracy is so esoteric that
| you need to level up the credibility of your sources of
| information.
| themgt wrote:
| The current "Out of Africa" is really not the same as what you
| might have learned 2-3 decades ago, despite the branding. David
| Reich is probably the leading researcher in this field and his
| description of our best guesses is highly nuanced and open to
| new data.
|
| https://www.youtube.com/watch?v=Uj6skZIxPuI
|
| https://www.razibkhan.com/p/out-of-africas-midlife-crisis
| enkid wrote:
| Out of Africa was fought by the majority of Western scientists
| during the early 20th century because of their pro-European
| biases. The reason its accepted is because the preponderance of
| evidence supports it.
| Mountain_Skies wrote:
| No doubt those biased Europeans felt their theory had the
| preponderance of evidence behind it. Funny how often the
| settled science is like that until the incumbent scientists
| die off rather than because better evidence was considered
| and adopted by science.
| anonymousDan wrote:
| I don't think it's some sort of conspiracy among
| scientists. A lot of the genetic sequencing techniques
| simply weren't possible until recently.
| whimsicalism wrote:
| there were also a lot of sociocultural changes coming out of
| the 60s/70s that changed the scientific conclusions we drew.
|
| 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.
| PittleyDunkin wrote:
| > 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.
|
| 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.
| whimsicalism wrote:
| I had a recent discussion about this, will try to pull up
| the sources, but my understanding is displacement is the
| majoritarian current and cultural shift with same
| population very much a secondary that only applies in a
| minority of the cases
|
| a lot of these admixture events show near total
| displacement of the y chromosome also
| PittleyDunkin wrote:
| 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.
|
| 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.
| nobody9999 wrote:
| >when modern populations are so genetically diverse.
|
| 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...
| PittleyDunkin wrote:
| > Are they? Are there any studies that confirm that
| hypothesis?
|
| ??? 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.
| nobody9999 wrote:
| You said: when modern populations are so
| genetically diverse.
|
| They are not. Humans _as a species_ (in case you 're not
| understanding what I mean by "species," I mean all the
| bipedal primates generally referred to as "Homo Sapiens")
| are _not_ very 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.
| drawkward wrote:
| Yes.
| throw3288932 wrote:
| > from European fossils dating back 45,000 years
|
| 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.
| PittleyDunkin wrote:
| > Would any evidence that contradicts the 'Out-of-Africa' dogma
| even get considered by Western scientists?
|
| 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.
| whimsicalism wrote:
| yes, see david reich
| zoombippy wrote:
| This doesn't account for shrinkage in the pool
| erichocean wrote:
| It's amazing how out of date this conception is with the actual
| research.
|
| I guess it's to be expected that pop-sci is 10-15 years behind...
| robwwilliams wrote:
| One error in this article by Zimmer that surprises me. He claims
| all modern humans have some admixture with Neaderthals but to the
| best of my knowledge this is not true of KhoiSan, Central African
| hunter gatherers, and several West African populations.
|
| Does Zimmer know something that I do not? Or David Reich?
| mmmrtl wrote:
| Hasn't backmigration/Eurasian admixture post-introgression made
| that true? iirc reference bias artefactually made African
| genomes look like they had no Neanderthal segments.
|
| https://www.cell.com/cell/fulltext/S0092-8674(20)30059-3
| https://www.pnas.org/doi/full/10.1073/pnas.1313787111
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