Journal of Anthropological Archaeology 26 (2007) 88–108 www.elsevier.com/locate/jaa The southern dispersal hypothesis and the South Asian archaeological record: Examination of dispersal routes through GIS analysis Julie S. Field ¤, Michael D. Petraglia, Marta Mirazón Lahr Leverhulme Centre for Human Evolutionary Studies, University of Cambridge, Downing Street, Cambridge CB2 3DZ, UK Received 6 October 2005; revision received 5 June 2006 Available online 27 July 2006 Abstract This research advances a model for coastal-based dispersals into South Asia during oxygen isotope stage (OIS) 4. A series of GIS-based analyses are included that assess the potential for expansions into the interior of South Asia, and these results are compared with known archaeological signatures from that time period. The results suggest that modern Homo sapiens could have traversed both the interior and coastlines using a number of routes, and colonized South Asia rel- atively rapidly. Use of these routes also implies a scenario in which modern H. sapiens, by either increased population growth or competitive ability, may have replaced indigenous South Asian hominin populations. © 2006 Elsevier Inc. All rights reserved. Keywords: South Asia; Human dispersals; Coastal routes; GIS; Modeling Over the last decade, archaeological research has maps of modern human expansions. Typically, the identiWed South Asia as a crucial new frontier in the route is represented by a broad arrow that sweeps study of human evolution. The presence of both fos- north-eastwards out of Africa ca. 45,000 years ago sil and lithic components throughout the region (kya), which then bifurcates into sub-branches that attests to Pleistocene colonization and occupation enter Europe, Siberia, and the northern portion of of the subcontinent by hominin populations (Ken- South Asia (Cavalli-Sforza et al., 1993; Foley, 1987). nedy, 2000; Misra, 2001). In terms of the region’s This route is purely illustrative, and is not the prod- colonization by modern humans, the general uct of either paleogeographical or paleoenviron- assumption is that Homo sapiens came from the mental analysis. In contrast, it has been suggested West, ostensibly from a Eurasian population that that earlier dispersals of modern humans may have had its roots in the Levant (Klein, 1999; Straus and taken place between ca. 70 and 45 kya, or during the Bar-Yosef, 2001). This premise is largely implicit in glacial conditions of oxygen isotope stage (OIS) 4 and the interstadial Stage 3 (Lahr and Foley, 1994, 1998; Oppenheimer, 2003; Stringer, 2000). These * Corresponding author. Fax: +44 1223 335 460. would have traced the coastlines of the Arabian E-mail address: [email protected] (J.S. Field). Peninsula and the Indian subcontinent, and the 0278-4165/$ - see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.jaa.2006.06.001 J.S. Field et al. / Journal of Anthropological Archaeology 26 (2007) 88–108 89 descendents of these people would have ultimately demographic expansions, and the movement of pop- colonized Australasia and Island Melanesia by ca. ulations within and beyond South Asia’s bound- 50 kya. The presence of sites dating to 42–47 kya in aries. Therefore, the paleoenvironment of the region Australia (O’Connell and Allen, 2004) provide the and its relation to human occupation represents an calibration point for this ‘Southern Dispersal’, important source of information on the factors implying that modern humans must have left Africa aVecting hominin evolutionary patterns in South prior to this date. The large numbers of sites across Asia. East Africa, the Arabian Peninsula, and South Asia Over a century of archaeological research in that are broadly attributable to the Middle Paleo- South Asia has revealed a wealth of late Pleistocene lithic also hint at the potential for human dispersals sites (Misra, 1989, 2001; Paddayya, 1984; Pappu and through these regions (James and Petraglia, 2005; Deo, 1994; Raju and Venkatasubbaiah, 2002). Petraglia, 2003; Petraglia et al., 2003). Unfortunately, fossils are extremely rare. In the Genetic studies support the colonization of South Narmada Valley, a hominin calvarium has been Asia by modern humans originating in Africa, and classiWed as Homo heidelbergensis (Cameron et al., more speciWc studies highlight the importance of 2004; Kennedy, 2000; Rightmire, 2001), and dated this region in the global expansion of particular lin- via associated fauna to 250–300 kya. For the rest of eages 50–70 kya (Forster, 2004; Kivisild et al., 2000; prehistory in South Asia, lithic assemblages and a Macaulay et al., 2005). Recent GIS-based analyses scattering of other artifacts have been used to deWne have produced the Wrst geographically explicit temporal units on the basis of technological sophis- model of this ‘Southern Dispersal Route’ along the tication, with reWnement contributed by relative and Indian Ocean rim, and also examined the environ- absolute dating methods. Generally, Middle Palaeo- mental conditions that may have aVected subsis- lithic industries (assemblages that are predomi- tence, migration speed, and demographic expansion nantly based on Xakes and prepared cores) date to had this route been employed in prehistory (Field as early as 150 kya (Misra, 1995), occur in abun- and Lahr, 2005). This work highlights the attractive- dance throughout South Asia, and in a variety of ness of South Asia to coastal foragers, and also sug- topographic contexts (Jayaswal, 1978; Paddayya, gests that portions of the route through this region 1984; Pal, 2002). Upper Paleolithic industries, which would have compelled populations to move inland. contain a greater number of blades and microliths, Field and Lahr also suggest that the presence of the appear as early as 45 kya (Dennell et al., 1992). Indus and Ganges–Brahmaputra deltas would have However, it must be noted that the Middle Paleo- served as full or partial barriers, keeping popula- lithic lithic industries of South Asia are exception- tions more or less within the conWnes of the South ally diverse. A recent assessment by James and Asian subcontinent, and encouraging expansions Petraglia (2005) outlines the regional diversity of into the interior. Recent genetic studies that indicate such industries in South Asia, as well as general reduced gene Xow between South Asia and the sur- trends towards the inclusion of Xake, blade and bla- rounding regions lend additional support to this delet industries at a few key sites. Elsewhere, these hypothesis (Metspalu et al., 2004). characteristics are commonly associated with mod- Moreover, preliminary studies of the genetic and ern H. sapiens, however, James and Petraglia note phenotypic signatures of South Asian populations that their sporadic occurrence in South Asia is more suggest that this region holds clues to understanding indicative of localized trends and independent the evolution and structure of human diversity out- invention, rather than the inXux of a new population side Africa. These signatures vary from the persis- (or species) with a distinctive tool kit. The potential tence of physical traits, such as skin color and body for a disassociation between H. sapiens and what is size, that may have originally developed in Africa, to typically identiWed as Upper Paleolithic/microlithic unique genetic sequences that may have evolved in raises a number of important issues for human evo- South Asia (Kivisild et al., 1999, 2003; Metspalu lution (Foley and Lahr, 1997). In particular, the et al., 2004; Vishwanathan et al., 2004). Although it behaviors that scholars usually identify as ‘modern’, is likely that demographic factors shaped much of the timing of dispersals out of Africa, the demogra- this diversity, the environment of the subcontinent, phy of hominins and modern humans, and the util- in particular geographical and ecological con- ity of ‘Middle/Upper Paleolithic’ typologies, become straints, would also have inXuenced diVerential rates open to re-interpretation. Additional archaeological of population growth, the source and extent of research in South Asia will undoubtedly clarify 90 J.S. Field et al. / Journal of Anthropological Archaeology 26 (2007) 88–108 these issues, but at the moment it is impossible to through other regions is not prohibited, but varies discern a uniquely modern H. sapiens signature according to relative measures of cost. In this study, from any deposits prior to 28 kya. However, the topography is the primary controlling factor for dis- hypothesis of a modern human occupation of the persals, although the extent of other geographic fea- region in the early Upper Pleistocene remains tures such as extents of sand seas or water gaps, also entirely feasible. serve as barriers. The present study, thus, aims to compare the Our analysis of dispersal routes is followed by the Middle Paleolithic archaeological record with a investigation of locations known to have been colo- hypothetical model of human dispersal and later nized by hominins (but not necessarily by H. sapi- demographic expansion, and discuss the implica- ens) in relation to dispersal routes and particular tions of the model in relation to chronologies and environmental conditions. The model anticipates prehistoric trends from particular areas. Although that modern human populations would have we will not be able to discuss the Wner details of encountered other hominins, most likely H. heidel- genetic and archaeological evidence in relation to bergensis or their descendants. Dispersals