February 22, 2015

Multiple opportunities for Out-of-Africa

Geology doi: 10.1130/G36401.1

Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal

Ash Parton et al.

The dispersal of human populations out of Africa into Arabia was most likely linked to episodes of climatic amelioration, when increased monsoon rainfall led to the activation of drainage systems, improved freshwater availability, and the development of regional vegetation. Here we present the first dated terrestrial record from southeast Arabia that provides evidence for increased rainfall and the expansion of vegetation during both glacial and interglacial periods. Findings from extensive alluvial fan deposits indicate that drainage system activation occurred during Marine Isotope Stage (MIS) 6 (ca. 160–150 ka), MIS 5 (ca. 130–75 ka), and during early MIS 3 (ca. 55 ka). The development of active freshwater systems during these periods corresponds with monsoon intensity increases during insolation maxima, suggesting that humid periods in Arabia were not confined to eccentricity-paced deglaciations, and providing paleoenvironmental support for multiple windows of opportunity for dispersal out of Africa during the late Pleistocene.



terryt said...

A very wide opportunity between 130 and 75,000. I know many will see the early MIS3 as the magic date but I think that is far too recent.

eurologist said...

Very useful, but I would be very careful to describe these as clear-cut ooA opportunities - especially the second half of the MIS 5 (ca. 130–75 ka) period, since to be successful, ooA also must mean out-of-Arabia, and from what we know of uniparental genetic research (and the presence of other, more ancient humans elsewhere), into habitable areas of the subcontinent and SE Asia, or close-by. In particular, it means at least being able to get to the Indus river and finding it actually flowing with water, and not finding much of India a tree-less semi-desert.

eurologist said...


I agree, MIS3 rater is the starting time for back-migrations from India, Pakistan, and Afghanistan into both the Levant (~50,000 ya) and Europe (~45,000 ya), since the deserts that had parted them vanished.

Christy Nelsen said...

Modern humans first arose between 100,000 and 200,000 years ago in Africa. But when and how the modern human lineage then dispersed out of Africa has long been controversial. Read complete article.