Out of Africa & archaeology

Dienekes points me to a new paper in Science which purports to add an archaeological layer of data to the "Out of Africa" paradigm which initially burst onto to the scene in the 1980s due to the molecular clock & mtDNA (though Chris Stringer and others long argued for a form of "Out of Africa" based purely on fossil morphology). The Independent has a good summary of the major points. The short of it is that this paper seems to suggest

a) One major Out of Africa event via the "Southern Route" (i.e., along the coast of southern Eurasia out of East Africa)

b) Subsequent radiations from India for all Eurasian lineages

c) Loss of complexity of toolkit in Australia

A few points. First, the general model is outlined in verbose detail in The Real Eve by Stephen Oppenheimer (not surprising, the genetics that the author of this paper appeals to comes out of the same labs that Oppenheimer used as his sources). The subtitle of Oppenheimer's book should have been, "Africa is the mother of us, but India is the mother of all non-Africans." Also, I find the argument for the loss of tool complexity in Australia due to isolation and cultural bottlenecks persuasive, Joe Heinrich at Emory has made the same argument about Tasmania in relation to Australia. Finally, genetics is neither necessary nor sufficient to "prove" the validity of a theory of human origins, so it is good to throw the limelight on other disciplinary methodologies which can help us triangulate the truth when it comes to questions in the historical sciences.

But what about the paper itself? There is a weak point which I think needs to be focused on: the author attempts to connect artefacts found in India 35 K BP and in East Africa 50 K BP, to show that there was a powerful and singular cultural continuity across the Southern Route. But 15,000 years is a long time. One issue in fossil science is that the dates given for a range of the existence of a species or of a culture are always narrower than reality because the nature of sample bias implies that the earliest and latest points in a range of existence will be "cut off" as a species or culture is either incipient and or near vanishing. In other words, 15,000 years is an overtestimate, nevertheless, is it plausible that the gap can be crossed? And is it plausible that human artefactual technologies could persist for tens of thousands of years? Some perspective: 15,000 years before the present would take us back to the last Ice Age, past Rome, past Sumer, past the Neolithic. But what about the Olduwan and Achuelean tool traditions, they persisted for hundreds of thousands, even millions of years across the span of the World Island (Eurasia + Africa).

Ah, but here is the likely answer I believe to the persistence of the Olduwan and Acheulean technologies: they weren't cultural traditions as we would understand them, rather, they were instinctive emergent behavioral properties of our proto-human ancestors' minds. Just as the Bowerbird builds because it must, that is its nature, so our "erectine" forbears were naturally "handy" with stone. There are even arguments that tool making was not utilitarian in a standard sense, but about male "display" and illustration of fitness. I won't address those issues, my point is just that modern technological traditions are relatively fluid, and change rather quickly. Though Sumerian or Roman toolkits tended to be very static compared to more recent epochs, nonetheless, they were prone to more change and natural development than "cultural" traditions which lasted for tens of thousands, let alone hundreds of thousands of years.

What does this have to do with the paper in question? If the exact same cultural tradition persisted for tens of thousands of years (a range given in the paper would be 75 K BP to 35 K BP) that is strong evidence to me that the perpetuators of that cultural tradition were not yet "human" in a the way we understand human, for humanity is protean, changeable, fickle and restless with creativity. On the other hand, it could be the relationship between the East African artefacts and the Indian ones is coincidence which happens to span tens of thousands of years, just as ancient eastern North American cultural traditions seem to bear some resemblance to the Solutrean tradition in Europe which predates it by 10,000 years. Myself, I lean toward the former, that is, that "modern" cognition, which allows for the explosive and unpredictable tacking of cultural traditions is a more recent innovation than we might have thought.

Addendum: Some might wonder about this paper's significance in light of my recent posts about admixture with non-African humans. This paper does not disconfirm that in the least because my overall argument is that total genome content is overwhelmingly "recent African," and that only at select loci which confer fitness advantanges would archaic introgression occur. We are all Africans ancestrally, but in some very significant ways some of us are not African, and might carry alleles within us that might be alien to humanity as we understand it as a recent African speciation even.

Graphic: Here is the map from the paper: