Why did modern human populations disperse from Africa ca. 60,000 years ago? A new model - PubMed (original) (raw)

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

Paul Mellars. Proc Natl Acad Sci U S A. 2006.

Erratum in

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 approximately 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.

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Conflict of interest statement

Conflict of interest statement: No conflicts declared.

Figures

Fig. 1.

Fig. 1.

mtDNA “mismatch” distributions of present-day African, Asian, and European populations, showing the frequency distribution of differences between pairs of individuals in the three populations. The modes of the three distributions clearly reflect a much earlier demographic expansion of African populations (ca. 80,000 B.P.), than those in Asia (ca. 60,000 B.P.) and Europe (ca. 40,000 B.P.) (–25).

Fig. 2.

Fig. 2.

Inferred patterns of geographical dispersal of the L2 and L3 mtDNA lineages in Africa between ca. 80,000 and 60,000 B.P., according to Forster (2). Later dispersals of the M, N, and R lineages into Asia and Europe after 65,000 B.P. derive from the L3 lineage.

Fig. 3.

Fig. 3.

Map of archaeological sites and early anatomically modern human remains in Africa and Israel, referred to in text.

Fig. 4.

Fig. 4.

Stone tools from the MSA Howiesons Poort levels at Klasies River (South Africa) dated to ca. 65,000 B.P., showing closely similar forms of blades, end scrapers, burins, and small, hafted segment forms to those found in European and Asian Upper Palaeolithic sites from ca. 45,000 B.P. onwards (32).

Fig. 5.

Fig. 5.

Fragments of red ochre incised with a complex geometrical design (A_–_D), and a series of deliberately perforated shells of Nassarius kraussianus (E) from the MSA levels of the Blombos Cave (South Africa), dated to ca. 75,000 B.P. (38, 39). [A_–_D reproduced with permission from Henshilwood et al. (38) (Copyright 2002, AAAS). E reproduced with permission from Henshilwood et al. (104) (Copyright 2004, AAAS).]

Fig. 6.

Fig. 6.

Summary of the model proposed here for modern human origins and dispersal from Africa.

Fig. 7.

Fig. 7.

Burial of an anatomically modern human skeleton at the Qafzeh Cave (Israel), accompanied by a large deer antler and dated to ca. 90,000–100,000 B.P. (73, 74).

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