Does Anyone *Actually* Believe in the Blank Slate?

[Trausti]

Another point to note, because the OP talks about natural selection as though it would boost his point: It absolutely doesn't, quite the contrary.

We have a situation where different subpopulations lived and procreated in relative but not absolute isolation -- sufficient isolation for the genomic footprints of different founding populations to be preserved over tens of thousands of years, and at the same time sufficient admixture to ensure that the last common ancestor lived only a few thousand years ago.

In such a situation, it's the neutral genes that will most closely track the original founder populations and thus show most difference: If, say, 90 percent of the ancestry lines of a San today, tracked back 5000 years, lead to someone who also lived in Southern Africa at that time while 90% of the lines from someone in Ireland lead back to someone living in Northeastern Europe, you expect statistically about 90% of their inert DNA to be derived from that population (both numbers are almost certainly too high, but let's go with them). But when we talk about variants that are subject to selection, all bets are off. While a variant with phenotypic effects will skip a subpopulation boundary as frequently as a neutral one, it'll spread much faster and thoroughly once it did.

In other words: Thanks to natural selection, human subpopulations are much more similar than expected from a simple drift+admixture model exactly where it matters most!

So true. When people have their DNA sequenced it turns out you can't tell at all where someone's ancestors came from. And everyone is equally susceptible to sickle-cell anemia. And is Lactose tolerant. And has the same Glomerular Filtration Rate. Etc.

 

[Trausti]

Ancient boy’s DNA pushes back date of earliest humans

 

[bilby]

<snip>[T]he question wasn't about (...) Irishmen and San, who are unlikely to be the most remote pair of human sub-populations in the world on a genetic basis.<snip>

Indeed.

If there are any living Mapuche (Patagonian natives) without a trace of European admixture (doubtful but possible), the most distance pair probably includes them. Who might be on the other end is more of an open question, but their counterpart is more likely to be found in Western Africa than in Southern Africa, as the latter has been the scene of massive and large-scale migrations and concommitant intermixture in the last two millennia (including a much more thorough European colonisation in the last few centuries, but also the Bantu migrations and Arab and Malay trade posts along the Indian Ocean shore before that) -- or possibly in Australia.

And *their* last common ancestor is still unlikely to have lived more than 3500 - 5000 years ago. Neither the Bering Strait nor the Torres Strait, and least of all the Sahara, were absolute barriers in pre-colonial times, though bottlenecks they may have been.

So in your world, Aboriginal Austrians and Pacific Islanders don't exist?

In my world, they are (almost literally) my next door neighbours. Of course, as I live in suburban Australia, Pacific Islanders are far more common in my area than Aborigines, but both groups are a notable presence in this part of town.

 

[Jokodo]

<snip>[T]he question wasn't about (...) Irishmen and San, who are unlikely to be the most remote pair of human sub-populations in the world on a genetic basis.<snip>

Indeed.

If there are any living Mapuche (Patagonian natives) without a trace of European admixture (doubtful but possible), the most distance pair probably includes them. Who might be on the other end is more of an open question, but their counterpart is more likely to be found in Western Africa than in Southern Africa, as the latter has been the scene of massive and large-scale migrations and concommitant intermixture in the last two millennia (including a much more thorough European colonisation in the last few centuries, but also the Bantu migrations and Arab and Malay trade posts along the Indian Ocean shore before that) -- or possibly in Australia.

And *their* last common ancestor is still unlikely to have lived more than 3500 - 5000 years ago. Neither the Bering Strait nor the Torres Strait, and least of all the Sahara, were absolute barriers in pre-colonial times, though bottlenecks they may have been.

So in your world, Aboriginal Austrians and Pacific Islanders don't exist?

In my world, they do and we know a bit more about them than the mere fact that they exist. In yours apparently that's all we know. You really need to freshen up your knowledge of (pre)history, geolinguistics, reproductive biology, and mathematics, to name but a few fields.


The outlying islands in the Pacific have only been inhabited for anything between 2000 and less than thousand years, so it's logically impossible that they've been isolated for more than 3-5000 years. For example, Hawaii was settled around 500 CE, New Zealand around 1200. The languages those settlers spoke are part of the  Malayo-Polynesian family, which originated in or around Taiwan no more than 5000 years ago and spread all the way to the Eastern Island off the South American coast to the East and Madagascar off the African coast to the West in the Common Era. Even those Islands that were settled significantly earlier (40000 years or more ago in the case of the Solomon Islands) were heavily influenced by that migration. Indeed, contact with the new migrants who brought technological innovations from the (Asian) mainland was intense enough for most of them to shift to the newcomers' language, as seen in this linguistic map of the Solomon Islands, where grey is Malayo-Polynesian:

View attachment 13412
(via  Languages_of_the_Solomon_Islands)

As for Aboriginal Austrians (sic!), their area has been, within the last 2000 years alone, invaded by Romans (including African mercenaries), people from modern Mongolia and/or nearby (two and a half times: the Huns and the Tatars, and Central Asian soldiers in the Soviet armies after WWII), Scandinavia (twice: during the migrations period and the Thirty Years' War), and the Middle East, and everywhere in between.

But assuming you meant Aboriginal Australians: One word: dingoes.
Dingoes arrived in Australia around 6000 years ago. That is at least 40000 years after the first humans arrived, around 6000 years after the land bridge with New Guinea was flooded, and around 6000 years before the commencement of European settlement. So, please tell us, do you think that dingoes:

I. swam to Australia, or
II. came to Australia by boat?
If the latter, do you believe that the boats they came on were:
a. steered by dogs, or
b. steered by humans?
if the latter, do you believe that the humans who steered those boats:
1) threw their dogs ashore and turned back, or
2) came ashore themselves?

Another word: Torres Strait Islands. Those are a group of islands, administered by Australia and situated between the Northern tip of Australia at Cape York Peninsula, and Papua New Guinea. The islanders in the North of the archipelago are horticulturalists growing the same crops as their neighbors on the mainland of New Guinea just a few miles away, with whom they've long had intensive contact - so much so that the Australian government has felt obliged to exempt PNG citizens visiting the islands for "traditional purposes" from visa requirements. The language they speak, however is, a large loanword vocabulary (including many words of Malayo-Polynesian origin, see above) notwithstanding, of  Pama–Nyungan stock, that is, belonging to the same family as 90% of the native languages on the Australian mainland all the way to Western Australia and Victoria!

So much about history and linguistics.



Coming now to reproductive biology and mathematics: Did you know humans reproduce sexually? Did you know this implies that the number of descendants an individual has grows quasi-exponentially with every generation?
This means that, when say around the year 0, a wave of migrations from the mainland brought the Pama-Nyungan languages to the Torres Strait, by the year 200 basically everyone in the straits had (Australian) mainland ancestry; when in the year 200, a small group of Torres Strait Islanders settled in mainland PNG, by 600 basically everyone in Southern New Guinea had Australian ancestry; when in the year 600, some South Papuans migrated to Western New Guinea, it means that by the year 1000, mostly everyone in Western New Guinea had Australian ancestors; when in the year 1000, a handful of Western Papuans came to the court of the  Sultanate_of_Ternate (a historical spice trade-based Muslim kingdom in Maluka with a sphere of influence extending into New Guinea), by 1250 everyone in the urban society in the Malukas had Australian ancestry; when in 1250, the Sultanate sent a delegation to the Khalif in Baghdad, while other members of its nobility went to Mecca for the Hajj, it means that by 1529, when the Ottoman army laid siege on Vienna, a ton of Middle Easterners had common-era Australian ancestors. So as of 2017, for every woman that was raped by an Ottoman soldier and for every Ottoman soldier that deserted and found refuge with the local population around the Siege of Vienna, there are now tens to hundreds of of thousands of Austrians (the real ones ) and other Central Europeans who had Aboriginal Australian ancestors within the last 2000 years.

 

[Jokodo]

Ancient boy’s DNA pushes back date of earliest humans

Once again you failed to read you very own link:

However early human evolution played out, later mixing and mingling of populations had a big genetic impact. DNA evidence from more recent fossils, including those studied by Schlebusch’s group, increasingly suggests that Stone Age human groups migrated from one part of Africa to another and mated with each other along the way (SN: 10/20/12, p. 9), says Harvard Medical School evolutionary geneticist Pontus Skoglund. In the Sept. 21 Cell, he and his colleagues report that DNA from 16 Africans, whose remains date to between 8,100 and 400 years ago, reveals a shared ancestry among hunter-gatherers from East Africa to South Africa that existed before West African farmers first arrived 2,000 years ago.

Translation, extra for you: Even before (Bantu) farmers arrived to Southern Africa (from Eastern Africa, but their ancestors in turn had come from Western Africa), there was genetic exchange between hunter-gatherer populations in different parts of the continent.

Comparisons to DNA from modern populations in Africa and elsewhere indicated that between 9 percent and 30 percent of Khoisan DNA today comes from an East African population that had already interbred with Eurasian people. Those East Africans were likely the much-traveled farmers who started out in West Africa and reached southern Africa around 1,500 years ago, the researchers propose.

Translation: Living Khoi-San have the equivalent of one grandparent to one great-grandparent who lived in Eastern Africa and immigrated to Southern Africa with the Bantu migrations less than 2000 years ago, and since Eastern Africa has always been in contact with Egypt, the Middle East, and other places along the Indian Ocean shoreline, this also means that all modern Khoi-San have ancestors living in Eurasia (and in increasingly smaller doses, beyond Eurasia, i.e. Australia and the Americas -- Jokodo) in the not-too-distant past.

 

[Jokodo]

Another point to note, because the OP talks about natural selection as though it would boost his point: It absolutely doesn't, quite the contrary.

We have a situation where different subpopulations lived and procreated in relative but not absolute isolation -- sufficient isolation for the genomic footprints of different founding populations to be preserved over tens of thousands of years, and at the same time sufficient admixture to ensure that the last common ancestor lived only a few thousand years ago.

In such a situation, it's the neutral genes that will most closely track the original founder populations and thus show most difference: If, say, 90 percent of the ancestry lines of a San today, tracked back 5000 years, lead to someone who also lived in Southern Africa at that time while 90% of the lines from someone in Ireland lead back to someone living in Northeastern Europe, you expect statistically about 90% of their inert DNA to be derived from that population (both numbers are almost certainly too high, but let's go with them). But when we talk about variants that are subject to selection, all bets are off. While a variant with phenotypic effects will skip a subpopulation boundary as frequently as a neutral one, it'll spread much faster and thoroughly once it did.

In other words: Thanks to natural selection, human subpopulations are much more similar than expected from a simple drift+admixture model exactly where it matters most!

So true. When people have their DNA sequenced it turns out you can't tell at all where someone's ancestors came from. And everyone is equally susceptible to sickle-cell anemia. And is Lactose tolerant. And has the same Glomerular Filtration Rate. Etc.

When people have their DNA sequenced to find out where (most of) their ancestors lived, what's used for diagnosing the result is the inert parts of the DNA. Also it's impossible, even theoretically, to use DNA sequencing to determine where all of an individual's ancestors lived even a couple hundred years ago. Look up "exponential growth", look up the length of DNA, and try to find out how long a strand of DNA has to be to be able to tell anything from it.

Sickle cell anemia is pretty much the worst example you could have come up with. It is a diagnostic of whether a person's ancestors lived in malaria-stricken regions within the last few hundred years and tells you literally nothing about which subpopulation from a few hundred thousand years they might be related to. The prevalence of the sickle cell trait varies between regions of one and the same country often by an order of magnitude (between 2.5% and 23.9% in Uganda, or between 1.4% and 19% in Italy). If you don't want to redefine "race" in such a way that Lowland Ugandans belong to one race along with Sicilians while Tuscans belong to another along with Highland Ugandans, you should forget about it right now!



Here, help yourself to some education:
http://www.thelancet.com/journals/langlo/article/PIIS2214-109X(15)00288-0/fulltext (Uganda, also the source of above map)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438445/ (Italy and Greece)

 

[Jokodo]

...And everyone is equally susceptible to sickle-cell anemia.

tl;dr re: my last reply: "Race" as defined by the US census bureau, or the continent where the majority of one's ancestors came from, may be a fairly good predictor of the likelihood of sickle-cell anemia in rural Alabama, where "white" or "Caucasian" means Scottish or English, but it's much poorer a predictor already in New York, where it can also mean Italian, Greek, or Lebanese, and flat fails at the global level.

And is Lactose tolerant. And has the same Glomerular Filtration Rate. Etc.

I don't know about GFR, but lactose tolerance is basically the same story: tied to ancestral diets within the last few thousand years, basically no connection to founder populations 10s or 100s of years ago, and cutting right across those.

 

[Jimmy Higgins]

Another point to note, because the OP talks about natural selection as though it would boost his point: It absolutely doesn't, quite the contrary.

We have a situation where different subpopulations lived and procreated in relative but not absolute isolation -- sufficient isolation for the genomic footprints of different founding populations to be preserved over tens of thousands of years, and at the same time sufficient admixture to ensure that the last common ancestor lived only a few thousand years ago.

In such a situation, it's the neutral genes that will most closely track the original founder populations and thus show most difference: If, say, 90 percent of the ancestry lines of a San today, tracked back 5000 years, lead to someone who also lived in Southern Africa at that time while 90% of the lines from someone in Ireland lead back to someone living in Northeastern Europe, you expect statistically about 90% of their inert DNA to be derived from that population (both numbers are almost certainly too high, but let's go with them). But when we talk about variants that are subject to selection, all bets are off. While a variant with phenotypic effects will skip a subpopulation boundary as frequently as a neutral one, it'll spread much faster and thoroughly once it did.

In other words: Thanks to natural selection, human subpopulations are much more similar than expected from a simple drift+admixture model exactly where it matters most!

So true. When people have their DNA sequenced it turns out you can't tell at all where someone's ancestors came from.

DNA sequencing can only tell you where people that share similar DNA live now. You can't use DNA to find out where your ancestors lived then.

 

[Bomb#20]

DNA sequencing can only tell you where people that share similar DNA live now. You can't use DNA to find out where your ancestors lived then.

That's rather like saying you can't use comparative anatomy to find out what your ancestors looked like, only what similar animals look like now, so we can't tell whether the common ancestors of monkeys and humans thirty million years ago looked like modern monkeys or modern humans. True, you can't just read off locations from DNA as if people didn't ever move; but you can use DNA as evidence to help determine which hypothesis about ancient location is most parsimonious.

Here's an example. Cavalli-Sforza's genetic map of Europe shows one principle component with a gradient from north to south. This tells us there was a significant migration along that axis, but tells us jack squat about whether the movement was north-to-south or vice-versa. On the other hand, the same map shows a different principle component forming concentric circles around Ukraine. This means either that a lot of people spread out from Ukraine, or that a lot of people with similar genes all over Europe independently moved toward Ukraine while people with more different genes stayed behind. Sometimes one hypothesis is a lot more parsimonious than the other.