Quaternary International 202 2009 2 13 Contents lists available at ScienceDirect Quaternary International journal homepage www elsevier com locate quaint The great arc of dispersal of modern humans Africa to Australia Stephen Oppenheimer School of Anthropology and Museum Ethnography Oxford University 51 Banbury Road Oxford OX2 6PE UK a r t i c l e i n f o a b s t r a c t Article history Available online 26 July 2008 During the Late Pleistocene anatomically modern humans AMH dispersed out of Africa across the continents Their routes obeyed the limitations placed on any large terrestrial mammal dependent on daily drinking water following certain climate permissive corridors AMH rst spread north with game across the Sahara to the Levant during the Eemian interglacial c 125 ka but failed to continue to Europe then occupied by Neanderthals The savannah ecosystem in North Africa and the Middle East then dried up and AMH vanished from the Levantine fossil record being replaced there by Neanderthals Later AMH successfully left Africa as a single group by the southern route to India The added ability to make short but deliberate open water crossings allowed them rst to cross the mouth of the Red Sea from Eritrea and subsequently Wallace s Line to reach the isolated Sahul continent at least by 48 000 years ago and possibly by 60 50 000 years ago They only nally arrived in Europe from South Asia around 45 50 000 years ago probably linked to climatic amelioration during OIS 3 2008 Elsevier Ltd and INQUA All rights reserved 1 Introduction The use of non recombining DNA and the phylogeographic approach based on reconstructed gene trees has been vital in illuminating the geography of the exit route of anatomically modern humans AMH their further travels and the logic of only one ultimately successful exit from sub Saharan Africa via the Yemen When did such events take place A multidisciplinary case can be made for an exit prior to the Younger Toba volcanic eruption of 74 ka YTE Chronometric predictions based solely on the genetic data have systematic problems and should be tested using data from archaeology Palaeo anthropology and the Earth Sciences The latter often having the best available dating and accuracy for periods earlier than the radiocarbon ceiling also offer insights for windows of opportunity based on sea level climate uctuations and even the occasional volcanic ash time marker There are three basic questions essential in any reconstruction of the African Exodus in the following logical order how many successful exits which routes and when Two further questions ride on the second two and are how and why 2 Regional setting In geographic terms the great arc of human dispersal was really a double ocean arc extending from the southern tip of Africa to the Fax 44 1865 437743 E mail address stephen oppenheimer anthro ox ac uk 1040 6182 see front matter 2008 Elsevier Ltd and INQUA All rights reserved doi 10 1016 j quaint 2008 05 015 southern tip of South America but this article refers to the primary modern human expansion from Africa round the coasts of the Indian Ocean to Melanesia and Australia in the Southwest Paci c Fig 1 The presumption that modern human range extension out of Africa proceeded initially along coastlines has depended largely on the rapidity of this movement as inferred from the genetic phylogeography and the very early dates of colonisation of Southeast Asia and Australia which will be discussed in this review For this speedy beach travel and the infferred mode and routes of expansion to be possible these explorers must have been able to exploit coastal marine resources Shell sh being limited in the intertidal zone have the tendency to be progressively overexploited necessitating extension along the beach This model clearly provides an immediate and continuous motive for range extension in a linear fashion Marine exploitation is characteristic of if not unique to modern humans and in one instance Neanderthals starting from at least 160 000 years ago Marean et al 2007 dates recently reviewed in McBrearty and Stringer 2007 Shell middens and other archaeological evidence show that the explorers were pro cient at such exploitation Middens and other evidence of marine exploitation are found on the African threshold at Abdur on the west coast of the Red Sea from 125 ka Walter et al 2000 at the very earliest occupation sites in Australia and most signi cantly in Timor at one of the oldest Asian human coastal occupation sites at the Australian threshold O Connor 2007 It is tempting to suggest that this new human skill complex and the ability to cross short stretches of water was an enabling even essential factor in expansion and could explain and date modern human expansion out of Africa Yet such determinist S Oppenheimer Quaternary International 202 2009 2 13 3 Fig 1 Outline map of modern human dispersals as reconstructed in this review From Oppenheimer 2003 conclusions should be tempered by knowledge of the earliest spread of Homo erectus to similar sites in Southeast Asia and the presence of Homo oresiensis in Flores near to Timor The fact that marine exploitation and a variety of other modern skills were practiced by modern humans in Africa twice as long as outside McBrearty and Stringer 2007 and owing to sea level changes cannot be found as dated evidence until further along the route rather blunts the value of such markers in determining motives dates routes and number of exits from Africa If these behavioural milestones made it so much easier to leave Africa why did anatomically modern humans not leave Africa much earlier and even many times over In this perspective regional and temporal climatic constraints are a more important source of information than any perceived behavioural revolution in determining dates for barriers and inviting corridors for our initial and unique spread out of Africa As will be seen the only discipline that at present reliably informs on number of exits is genetic phylogeography A combined approach should give increased con dence by triangulation The study of the geographic spread of gene lines involves three related types of inference rst an unambiguous gene tree e g Fig 2 is built up by sequence study of a stretch of nonrecombining DNA in representative population samples This review refers to maternally transmitted mitochondrial DNA mtDNA The non recombining part of the Y chromosome maleNRY produces very similar results Oppenheimer
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