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.
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.
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.
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.
> 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.
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.
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.
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?
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.
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"
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?
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.
They where all nomadics, so the concept of a village did not exist yet. It was more like family related moving groups, or maybe "clans". That said, at an individual level there was probably a concept of people exchange when meeting another group, or banning of an individual.
yeah, can replace "village" with "group of people" like families or clans. Basically just 'we blame you for our problems so you need to leave' type of situation.
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.
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.
I don't see how you could say that's more likely without evidence, lack significant gaps in archaelogical finds between eras of human presence in a region.
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
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.
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.
