Why did modern human populations disperse from Africa ca. 60,000 years ago? A new model

Abstract

Recent research has provided increasing support for the origins of anatomically and genetically “modern” human populations in Africa between 150,000 and 200,000 years ago, followed by a major dispersal of these populations to both Asia and Europe sometime after ca. 65,000 before present (B.P.). However, the central question of why it took these populations ≈100,000 years to disperse from Africa to other regions of the world has never been clearly resolved. It is suggested here that the answer may lie partly in the results of recent DNA studies of present-day African populations, combined with a spate of new archaeological discoveries in Africa. Studies of both the mitochondrial DNA (mtDNA) mismatch patterns in modern African populations and related mtDNA lineage-analysis patterns point to a major demographic expansion centered broadly within the time range from 80,000 to 60,000 B.P., probably deriving from a small geographical region of Africa. Recent archaeological discoveries in southern and eastern Africa suggest that, at approximately the same time, there was a major increase in the complexity of the technological, economic, social, and cognitive behavior of certain African groups, which could have led to a major demographic expansion of these groups in competition with other, adjacent groups. It is suggested that this complex of behavioral changes (possibly triggered by the rapid environmental changes around the transition from oxygen isotope stage 5 to stage 4) could have led not only to the expansion of the L2 and L3 mitochondrial lineages over the whole of Africa but also to the ensuing dispersal of these modern populations over most regions of Asia, Australasia, and Europe, and their replacement (with or without interbreeding) of the preceding “archaic” populations in these regions.

Cultural and human dynamics in southern Arabia at the end of the Middle Paleolithic

“…So far a migration flow across southern Arabia ca. 60e50 ka of African AMH groups introducing a number of technological and symbolic innovations in Eurasia, as speculated by the Out of Africa 3 model (Mellars, 2006), is not supported by any archaeological evidence. The populations who were present in southern Arabia at the beginning of MIS 3, at Wadi Surdud and Jebel Faya (A and B) in particular, do not appear to have introduced new behavioral skills into the region.…”

Body composition and susceptibility to type 2 diabetes: an evolutionary perspective

“…Australasia was reached at least 220 50,000 years ago, and the North American continent rather more recently. 50,51 The pattern 221 of dispersal has clearly contributed to contemporary human diversity, mediated by the 222 regional geographical routes taken, contrasting selective pressures, and periodic local 223 isolations, all of which have promoted inter-group differences and some genetic 224 diversification. 52,53 Despite this, our species is characterised by remarkably high levels of 225 genetic unity, 54 fundamentally linked with our high levels of phenotypic plasticity.…”

Evolution of human-driven fire regimes in Africa

“…Here we present a modeling approach that integrates information on the physics of fire spread (19)(20)(21), the effect of humans on different components of fire spread (8,22,23), and the paleoecology of modern humans (24)(25)(26). We use conceptual links between (i) known advances in human manipulation of fire, population growth, and spread and (ii) the parameters of a spatially explicit fire propagation model, to explore the types of impacts humans could have had on fire regimes as they learned to manipulate fire, their environment, and their landscapes.…”