Discussions on the history and historiography of Australia's New England

Friday, September 22, 2017

New DNA results shed light on African migration patterns

Researchers in Malawi examine bone fragments whose DNA provided input into a significant study of African migration patterns. Photo New York Times
There is an interesting article in Cell, Reconstructing Prehistoric African Population Structure. The summary reads:

"We assembled genome-wide data from 16 prehistoric Africans. We show that the anciently divergent lineage that comprises the primary ancestry of the southern African San had a wider distribution in the past, contributing approximately two-thirds of the ancestry of Malawi hunter-gatherers 8,100–2,500 years ago and approximately one-third of the ancestry of Tanzanian hunter-gatherers 1,400 years ago. We document how the spread of farmers from western Africa involved complete replacement of local hunter-gatherers in some regions, and we track the spread of herders by showing that the population of a 3,100-year-old pastoralist from Tanzania contributed ancestry to people from northeastern to southern Africa, including a 1,200-year old southern African pastoralist. The deepest diversifications of African lineages were complex, involving either repeated gene flow among geographically disparate groups or a lineage more deeply diverging than that of the San contributing more to some western African populations than to others. We finally leverage ancient genomes to document episodes of natural selection in southern African populations"

The New York Times (21 September 2017) carried a useful story by Carl Zimmer, Clues to Africa’s Mysterious Past Found in Ancient Skeletons, which provides some useful supplementary material.


Johnb said...

You can see the progress being made Jim as the 2012 study above states " San are descendants of the earliest diversification event in the history of all humans -- some 100,000 years ago, well before the 'out-of-Africa' migration of modern humans." Yet on the same page is a 2016 study " Researchers report strong evidence of an interbreeding event between Neanderthals and modern humans occurring around 100,000 years ago, much earlier than any previously documented." Current knowledge has it that Neanderthals were entirely absent from Africa so any interbreeding occurred outside Africa with human populations who had already left Africa if that was their origin. I believe the San are the key extant African population for understanding the journey of homo s. through time in Africa and a key finding for Africa was the divergence 30/40k BP of the Khoe from the original San population. So the San as a population must pre-date that event. It still leaves them as potentially relative late comers vis a vis the Australian Aboriginal and their journey. We know the Australians encountered Neanderthal first then Denisovan to arrive in Australia at least 60kBP so you could hypothesise that the Australian Aboriginal encounter with Neanderthal was at least in West Asia, if not further West and at least 80k BP if not earlier, that is they are likely related to those first homo s. known to have inter bred with Neanderthal. I am of course also related but to a much murkier degree.

Jim Belshaw said...

Interesting, John. I await new discoveries with anticipation!