Monday, April 9, 2018

Modern Human Remains In Arabia 86,000 Years Ago

Tools associated with modern humans in inland Arabia have suggested that modern humans arrived there ca. 125,000 years ago, but modern human remains are much more powerful evidence and the latest find on that front is from at least 86,000 years ago.
Understanding the timing and character of the expansion of Homo sapiens out of Africa is critical for inferring the colonization and admixture processes that underpin global population history. It has been argued that dispersal out of Africa had an early phase, particularly ~130–90 thousand years ago (ka), that reached only the East Mediterranean Levant, and a later phase, ~60–50 ka, that extended across the diverse environments of Eurasia to Sahul. However, recent findings from East Asia and Sahul challenge this model. Here we show that H. sapiens was in the Arabian Peninsula before 85 ka. We describe the Al Wusta-1 (AW-1) intermediate phalanx from the site of Al Wusta in the Nefud desert, Saudi Arabia. AW-1 is the oldest directly dated fossil of our species outside Africa and the Levant. The palaeoenvironmental context of Al Wusta demonstrates that H. sapiens using Middle Palaeolithic stone tools dispersed into Arabia during a phase of increased precipitation driven by orbital forcing, in association with a primarily African fauna. A Bayesian model incorporating independent chronometric age estimates indicates a chronology for Al Wusta of ~95–86 ka, which we correlate with a humid episode in the later part of Marine Isotope Stage 5 known from various regional records. Al Wusta shows that early dispersals were more spatially and temporally extensive than previously thought. Early H. sapiens dispersals out of Africa were not limited to winter rainfall-fed Levantine Mediterranean woodlands immediately adjacent to Africa, but extended deep into the semi-arid grasslands of Arabia, facilitated by periods of enhanced monsoonal rainfall.
H.S. Groucutt et al. "Homo sapiens in Arabia by 85,000 years ago." Nature Ecology & Evolution. (April 9, 2018) doi:10.1038/s41559-018-0518-2.

Commentary by the authors of the paper notes that:
According to the old textbook view, our species evolved in Africa about 200,000 years ago. Despite a brief, failed expansion to the edge of Eurasia about 100,000 years ago when humans first tried migrating to the lands at the eastern end of the Mediterranean (the Levant), we only successfully spread out of Africa around 60,000 to 50,000 years ago. 
Recent evidence suggests that much of this narrative is wrong. Findings in Africa, such as from the site of Jebel Irhoud in Morocco, suggest that Homo sapiens appeared early, more than 300,000 years ago. Our origin does not seem to have occurred in only one small area, but across much of Africa. 
Findings from the Levant, most recently the dating of a maxilla (upper jawbone) from Misliya Cave in Israel, suggest our species repeatedly expanded into the winter-rainfall fed, forested area just outside Africa. We don’t yet know if people survived long term in the Levant, which is a very small area. It seems more likely that there were repeated migrations from Africa. 
But what about the areas beyond the Levant? Recent findings suggest that our species got to East Asia and Australia much earlier than had been thought. But determining the hominin species present and the age of these sites have proven challenging. 
Our finger fossil gives us a more specific time range to work with, which correlates with other evidence. Stone tools from Al Wusta are similar to those from the Middle Palaeolithic (Stone Age) period in the Levant and north-east Africa. They suggest that our early spread into Eurasia was not associated with some kind of technological breakthrough, such as the invention of projectile technology as some have suggested
Together, these findings show that Homo sapiens had spread beyond the Levant much earlier than traditional accounts would have it. The Al Wusta phalanx is the oldest directly dated fossil of our species beyond Africa and the Levant and so represents a crucial reference point in understanding this topic.
Here is a link to images of arrowheads found by the same investigator.

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