I’ve long suspected (given the archaeological evidence, like 80,000 year old human remains in China,) that there were two Out of Africa (OOA) events–an early one that headed east, toward Australia, and a later one that headed everywhere (including Australia)–and now it looks like this has been genetically confirmed:
Isn’t this a great graphic? My hat’s off to the Estonians. Beautiful work.
Here’s another one they made (sadly small) with less color and more detail on the Eurasian lines. (IIRC, Chinese have more Neanderthal ancestry than Europeans, so technically the schematic ought to be a wee bit more complicated than this, but it’s already complicated enough and this is a solid general overview.)
It might just be the sleep dep + lots of coffee talking, but I am so excited about this.
Some quotes from the NY Times article:
In Israel, for example, researchers found a few distinctively modern human skeletons that are between 120,000 and 90,000 years old. In Saudi Arabia and India, sophisticated tools date back as far as 100,000 years.
Last October, Chinese scientists reported finding teeth belonging to Homo sapiens that are at least 80,000 years old and perhaps as old as 120,000 years. …
Examining their data separately, all three groups came to the same conclusion: People everywhere descend from a single migration of early humans from Africa. The estimates from the studies point to an exodus somewhere between 80,000 and 50,000 years. …
n Papua New Guinea, Dr. Metspalu and his colleagues found, 98 percent of each person’s DNA can be traced to that single migration from Africa. But the other 2 percent seemed to be much older.
Dr. Metspalu concluded that all people in Papua New Guinea carry a trace of DNA from an earlier wave of Africans who left the continent as long as 140,000 years ago, and then vanished.
Obviously, in science, replication and caution are key. Don’t get too excited. These results might turn out to be wrong–sometimes samples get contaminated or data coded incorrectly and we get results that turn out to be completely wrong. And, okay, this isn’t really “huge” in the grand scheme of things–we’re only talking about 2% of Papuans’ ancestors, not, like, 40% of them. But it does explain all of those anomalously old findings.
Now someone needs to explain the Red Deer Cave People:
The Red Deer Cave People were the most recently known prehistoric Hominin population that did not look like modern humans. Fossils dated to between 14,500 and 11,500 years old were found in Red Deer Cave and Longlin Cave in China. Having a mix of archaic and modern features, they are (tentatively) thought to be a separate species of humans that persisted until recent times and became extinct without contributing to the gene pool of modern humans.
On a related note, we have some awesome news about Aborigine DNA/language trees: A genomic history of Australia and Why Australia is home to one of the Largest Language Families in the World. (Well duh it’s because Aborigines spent thousands of years as tiny bands of hunter gatherers, in which each isolated band started developing its own language.) These articles have an oddly inverted structure, (burying the lead, I guess,) so let’s rearrange the abstract for coherency:
We estimate that Aboriginal Australians and Papuans diverged from Eurasians 51–72 kya, following a single out-of-Africa dispersal, and subsequently admixed with archaic populations. … Papuan and Aboriginal Australian ancestors diversified 25–40 thousand years ago (kya), suggesting pre-Holocene population structure in the ancient continent of Sahul (Australia, New Guinea and Tasmania). However, all of the studied Aboriginal Australians descend from a single founding population that differentiated ~10–32 kya. We infer a population expansion in northeast Australia during the Holocene epoch (past 10,000 years) associated with limited gene flow from this region to the rest of Australia, consistent with the spread of the Pama–Nyungan languages.
(kya = thousand years ago). So about 10-32 thousand years ago, one group of Australians conquered all of the other groups of Australians.
The science article notes:
To the researchers’ amazement, the genetic pattern mirrored the linguistic one. “It’s incredible that those two trees match. None of us expected that,” says paleoanthropologist Michael Westaway of Griffith University, Nathan, in Australia, a co-author on the Willerslev paper. “But it’s confusing: The [genetic splits] date to 30,000 years ago or more but the linguistic divisions are only maybe 6000 years old.”
Willerslev says he first thought the languages must be much older than thought. “But the linguists told me, ‘no way.'”
Both types of data also show that the population expanded from the northeast to the southwest. This migration occurred within the last 10,000 years and likely came in successive waves, Bowern says, in which existing languages were overlaid by new ones. This expansion also seems to correspond with a stone tool innovation called a backed edge blade. But the accompanying gene flow was just a trickle, suggesting that only a few people had an outsize cultural impact, Willerslev says. “It’s like you had two men entering a village, convincing everyone to speak a new language and adopt new tools, having a little sexual interaction, then disappearing,” he says. Then the new languages continued to develop, following the older patterns of population separation. “It’s really strange but it’s the best way we can interpret the data at this stage.”
Three things going on here. 1. The group from the north conquered the group from the south, raped their women, and imposed their language. They were able to do this because they had better weapons (“backed edge blades.”) But the group from the north was not very big, and so did not leave a very big genetic signature.
2. They conquered an existing population structure, at which point their language got absorbed into that structure, probably picking up some linguistic substrate from the groups’ previous languages along the way. Since most people learn language from their parents, it’s not too surprising to find cases where language and genetics line up. (Note that people do not always learn languages from their parents.)
3. Intellectuals are kind of naive.
The other really interesting thing here is that the linguistics team came to their conclusions by feeding a big database of Aboriginal words into a computer and having it run similar algorithms to the ones geneticists use for examining human ancestry (see the lovely graphics above.) I’ve been wondering for a long time why they don’t just do this, and am excited that they finally are.
Now please someone put all of the languages + reconstructed proto-langauges into the computer and find the most likely trees.
(Sorry, Nick. The regularly scheduled Anthropology Friday is going to have to wait a week. There just aren’t enough days.)