Tuesday, April 25, 2017

Neanderthals and the great leap forward

Razib Khan writes:
In the year 2000 I broadly accepted the thesis outlined a few years later in The Dawn of Human Culture. That our species, our humanity, evolved and emerged in rapid sequence, likely due to biological changes of a radical kind, ~50,000 years ago. This is the thesis of the “great leap forward” of behavioral modernity.

Today I have come closer to models proposed by Michael Tomasello in The Cultural Origins of Human Cognition and Terrence Deacon in The Symbolic Species: The Co-evolution of Language and the Brain. Rather than a punctuated event, an instance in geological time, humanity as we understand it was a gradual process, driven by general dynamics and evolutionary feedback loops.

The conceit at the heart of Robert J. Sawyer’s often overly preachy Neanderthal Parallax series, that if our own lineage went extinct but theirs did not they would have created a technological civilization, is I think in the main correct. ...

One of the major holy grails I see now and then in human evolutionary genetics is to find “the gene that made us human.” The scramble is definitely on now that more and more whole genome sequences from ancient hominins are coming online. But I don’t think there will be such gene ever found.
The two competing claims are that (1) humans radically advanced biologically 50k years ago; and (2) Neanderthals had what was needed to evolve into a technological civilization.

Why can't these both be true? Maybe Neanderthals had that magic gene or set of genes, and Africans did not, and maybe the Neanderthal-African hybrids of 50k years made that great leap forward only because their inherited those magic Neanderthal genes.

Nobody seems to consider this possibility, and maybe there is some technical reason for rejecting it, but I don't see it. Recent research has shown that Neanderthals were more advanced than anyone thought, and that the biggest human advances came after Neanderthal interbreeding.

Wikipedia says
The Late Upper Paleolithic Model, or Upper Paleolithic Revolution, refers to the idea that, though anatomically modern humans first appear around 150,000 years ago, they were not cognitively or behaviorally "modern" until around 50,000 years ago, leading to their expansion into Europe and Asia.[6][17][18] These authors note that traits used as a metric for behavioral modernity do not appear as a package until around 40–50,000 years ago. Klein (1995) specifically describes evidence of fishing, bone shaped as a tool, hearths, significant artifact diversity, and elaborate graves are all absent before this point.[6] Although assemblages before 50,000 years ago show some diversity the only distinctly modern tool assemblages appear in Europe at 48,000.[17] According to these authors, art only becomes common beyond this switching point, signifying a change from archaic to modern humans.[6] Most researchers argue that a neurological or genetic change, perhaps one enabling complex language such as FOXP2, caused this revolutionary change in our species.[6][18]
That was exactly the time that African interbred with Neanderthals, according to the latest DNA evidence.

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