I came across this interesting book chapter on The "Upper Paleolithic" of South Arabia by Jeffrey Rose and Vitaly Usik. I first became aware of Dr. Rose's work in Southern Arabia when I watched the "Incredible Human Journey" (see Related links below) a couple of years ago. The conclusions of the chapter seem to mesh quite well with some of my recent thoughts about a possible Out-of-Arabia expansion of modern humans, posterior to the earlier Out-of-Africa.
The following figure is instructive:
Notice the super-aridity of MIS 4, circa 70ka BP. This would certainly be an awful time for anyone to move into Arabia. Conversely, if there were anatomically modern people living there prior to MIS 4, the onset of the super-arid phase during MIS 4 would be a great time to get out.
As I mention in my previous post on mtDNA haplogroup L3, I think that the major human expansion associated with haplogroup L3 and its M/N subclades originated in Arabia, and the super-arid MIS 4 phase looks about right for a bottleneck out of which the descendants of only a single woman, the L3 ur-mother would survive.
From the book chapter:
So, we are able to make a few general observations regarding the Upper Paleolithic found in the southern portions of the peninsula: (1) there are multiple phases of human occupation in South Arabia throughout the latter half of the Upper Pleistocene, (2) there are elements loosely related to the Levantine sequence, however, the South Arabian Upper Paleolithic probably belongs to a unique and locally-derived lithic tradition, (3) there do not appear to be any links with East Africa (with the exception of the Hargeisan) from MIS 4-onward, and (4) assemblages from southern and south-western Arabia are dominated by different laminar-based technologies between 75 and 8 ka.
The Hargeisan is interesting, because it is a possible link of an expansion from Arabia to Africa:
One potentially additional piece of evidence for this hypothesized Near Eastern/Arabian-derived human expansion is the anomalous Hargeisan Industry found in the Horn of Africa. Known from a small number of findspots around Hargeisa (Clark, 1954), Boosasso (Graziosi, 1954) and Midhishi Cave in the Golis Mountains of northern Somalia (Gresham, 1984; Brandt, 1986), the Hargeisan has been found overlying MSA material and beneath LSA occupation layers.
Of course, the political situation in Somalia may suggest that scientists won't be studying the Hargeisan anytime soon.
More from the book chapter:
From an archaeological perspective, Straus and Bar-Yosef (2001: 2) entertain the same possibility: “there is, however, no reason a priori to exclude the possibility that intercontinental contacts occurred on a two-way street, especially at Suez, via Sinai, or across the shallow Bab al Mandab, so close to that corridor to sub-Saharan Africa, the Nile.” Marks (2005) and Otte et al. (2007) envisage similar scenarios during the MP/UP transitions in the Near East and Zagros regions. Both scholars argue that the archaeological evidence from Eastern Europe and Western Asia indicate the expansion of European UP technologies radiated from these areas, rather than Africa, during early MIS 3. Echoing this proposition from a biological perspective, Schillaci (2008) proposes the spread of Levantine-derived peoples into Australasia between 60 and 40 ka based on fossil evidence and phylogenetic relationships between populations.
We maintain that the evidence from Arabia indicates the post-MIS 4 human expansion did not originate in sub-Saharan Africa; rather, early modern humans have emerged from a geographic range encompassing areas of northeast Africa, Western Asia, Arabia, and South Asia. These populations would have been forced to contract into environmentally stable refugia around Arabia such as the Ur-Schatt River Valley, coastal oases, Yemeni Highlands, and/or the Dhofar Mountains during climatic downturns. As such, the fluctuating dynamic between landscape carrying capacity and population density may have been a critical mechanism driving early human dispersals from the region. Episodes of climate change caused large portions of the Arabian peninsula to become uninhabitable due to such calamities as the inundation of the emerged continental shelf and desertification throughout the interior. Given the potential importance of these once favorable, now uninhabitable zones, future investigations in and around Arabia should endeavor to explore the heart of the desert and bottom of the sea.