3 African Background to Eurasian Prehistory : Dispersals

Ravi Korisettar

. Introduction

Dispersal is an essential element of the evolutionary process for all organisms. Most species start as small localized populations, and if successful spread more widely to fill up the available habitat. The rate and direction of any such dispersal are functions of the ability of the species to survive and thrive in the environments encountered and of its own … Human evolution fits into this biogeographic pattern. From their localized African origins humans have come to live all over the world, and that can only have happened as a result of dispersals (Lahr 2006: 407).

Evolutionary anthropologists would like to consider dispersal as a form of adaptive behaviour in the event of calamity, demographic pressure, etc., which compel colonisation of suitable new habitats with congenial environments so that populations survive the adversity. However, Archaeologists would like to address the question of what specific conditions compelled hominins‟ expansion out of Africa. There may have been multiplicity of reasons triggering wider territorial movement, but the focus seems to be on bio-cultural and changing climatic conditions.

2. DISPERSALS

In the context of human exodus out of Africa two major expansion events are under consideration, though scholars are of the view that there were multiple expansions out of Africa since the emergence of Homo in eastern Africa. The Out of Africa I refers to the first hominin expansion into Eurasia and is riddled with a conflict of long and short chronology. The Out of Africa II refers to expansion of anatomically modern humans (AMHs) since their emergence in Eastern Africa and is equally confronted by the arguments similar to the first Out of Africa. Here again there are issues relating to long and short chronologies: expansion associated with early Homo sapiens or with later expansion accompanied by symbolic or modern behaviour, including the invention of backed blade Microlithic technology (i.e. Out of Africa III).

3. Out of Africa Expansions: The Long and Short Chronologies

Despite suggestion from scholars that human expansion might have taken place prior to the emergence of Homo in Africa, the overwhelming evidence is in favour of expansion post erectus emergence, and typical Oldowan sites are as yet known from outside of Africa. The current Out of Africa expansion models have focused on human exodus after the emergence of Homo. The dating of Lower Palaeolithic and Homo fossil bearing localities outside of Africa in Europe, East and Southeast Asia have given rise to two conflicting schools of thought: (a) Long chronology and (b) Short chronology. They have persisted in the Palaeo-anthropological debate as of date. These schools of thought have continued to make intensive arguments basing themselves on reinvestigations at older sites and application of refined chronometric methods. The concept of short and long chronology has also been extended to the recent African origins of modern humans and the peopling of the globe by modern humans, though the time span involved is different.

With the growing body of multidisciplinary data from both early Homo and AMH sites in Europe and Asia several new perspectives have emerged contributing to the intensity of debate. Arabia and Indian subcontinent are now at the centre of debate on hominin expansion out of Africa and have thrown up dated evidence in favour of long chronology for both the major expansion events in human prehistory. There is a plethora of terminologies dealing with these issues: genetic, technological and contextual area perspectives on this debate which do not seem to converge as yet.

In both the expansion events the short chronology adherents consider the existence of older sites in the critical geographical area, between the Caucasus and Mediterranean-Levant, as either intermittent occupations or as part of failed expansion event (especially AMHs). Typo-technological variation in the lithic assemblages along the identified dispersal paths have been attributed to the founder effect. This may also mean adaptation to varying food resources along the path or owing to dependence on land based food resources.

The eastern expansion of Homo sapiens is speculated to have taken place along the southern arc, which is popularly known as Southern Dispersal. Two distinct paths of dispersion have been competing for gaining universal acceptance under the growing body of archaeological and genetic evidence. They include (a) northern route and (b) coastal route. Either of these paths led modern humans to the northern shores of Australia (Sahul) through an ocean crossing around Indonesia (Sunda). There is ongoing considerable debate among Prehistorians regarding the suitability of either of these routes and cite the archaeological material in support of the routes of dispersal.

4. Out of Africa I

The long chronology for the Lower Palaeolithic settlements outside Africa in the Old World is based on the dates for Dmanisi 1.8 Myr (Eastern Europe, Caucasus), Yuanmou 1.7 Myr (China), and Sangiran 1.6 Myr (Java). In recent years the Iberian sites have produced late Early Pleistocene dates (pre-and post-Jaramillo event) with sites like Fuente Nueva3, Barranco Leon D and Sima del Elefante in the time range of 1.07-0.9 Myr. All these dates are synchronous with the Jaramillo magnetochron (~ 1.09 Myr).

The short chronology for the European settlement is based on the arguments that Pre-Jaramillo settlements were intermittent in nature and were restricted to the Mediterranean area. The short chronologists argue that climatic and ecological barriers obstructed early entry of Homo into Europe and emphasize on the limitations of the ESR Dating methods. The onset of a dry phase during MIS 22 is considered to have exerted selective pressure on the Ethiopian mammals and humans in North Africa and led to large scale migration into the Mediterranean region and southern Europe.

This episode of human expansion into Western Europe is known as follow-the-herd hypothesis. This hypothesis does not fit the explanation for early occupation of Europe around 1.8 Myr in the Caucasus (Dmanisi) as the associated mammalian fauna is typically Asian origin. In defence of this Garcia et al. (2014: 93) argue that this first expansion was “as a result of biological evolution, technological development and increased social organization.”

The long chronology is based on the multipronged approach, including a combination of radiometric, magneto stratigraphic and bio stratigraphic methods and provide a revised age estimates for the Iberian sites, including Sima del Elefante c. 1.2 Myr, Gran Dolina (TD3-4 and 5) and Vallparadis (EVT 17) between 1 and 0.9 Myr, Gran Dolina (TD6) is placed 0.8 Myr. Thus they show a continuity from Jaramillo event.

Long and short chronologies for the first human population of Europe and the Indian subcontinent have come under serious scrutiny. In view of the recent dating efforts as well as multidisciplinary investigations at the Spanish and Georgian sites in Europe and geo-chronology of the Lower Palaeolithic sites in the Indian subcontinent there has been considerable swing in favour of long chronology both in India and Europe.

Early Homo erectus expansion out of Africa is generally attributed to cultural innovations such as stone tools of the Acheulian type, controlled use of fire and social bonding and physiological adaptability, particularly fulltime bipedalism.

5. Out of Africa II: Background

The Out of Africa model of peopling of the world insists on tracing the origins of: (a) anatomically modern humans; (b) modern human behaviour; (c) the development of radial core and Levalloise technologies; (d) crescentic backed blade technology; and (e) projectile composite tools [points in particular] to Africa. Although there is no conflict regarding these events, that enabled replacement of archaic populations across the Old World and eventually the colonization of the New Worlds [including Australia and the Americas] much debate has ensued owing to inconsistency in the multidisciplinary data emanating from ongoing research on: (a) mtDNA and Y-chromosome analyses of worldwide living populations and fossil hominins; (b) Palaeo-environmental, Palaeo-geographical and tectonic stability analyses of the regions occupied by the immigrant hominins, particularly along the suggested corridors of dispersal; and (c) absolute chronology of Middle and Late Pleistocene lithic industries outside of Africa, which do not converge onto a unified model. This Out of Africa model conveniently excludes inner Asia and the Far East continental areas from the ambit of dispersal and regional diversity in hominins. To date, the chronologically oldest fossil of Homo sapiens lay in Eastern Africa. Africa is also the region of greatest diversity in mtDNA among living populations, indicating that the hotspot of modern human evolution lies here.

Prior to the emergence of molecular analyses of living populations in the mid-1980s, a morphological analyses of the fossils suite of Homo sapiens from Africa, Europe and East and Southeast Asia had given rise to formulating the Multi-regional model and its variants. The East Asian Palaeo-anthropologists are as yet uncomfortable with the Out of Africa model, though it may be inevitable.

The Out of Africa debate also focuses on the timing and nature of eastward expansion of modern humans out of Africa and lays emphasis on the geographical importance of the Indian subcontinent, in view of recent well dated Middle and Upper Palaeolithic sites reported from southern India and considers this region as a half way house between Africa in the west and Australia in the east. This model‟s chief concern is how fast the immigrant modern hominins dispersed along a coastal corridor, either episodically or as a single event. Both Arabian and Indian Peninsulas have been considered gateways into Asia especially in the Southern Dispersal model. While one school advocates a single rapid dispersal (endowed with Mode IV microlithic package) event the other school advocates multiple dispersal events (endowed with Mode III and Mode IV lithic packages).

The growing body of archaeological records of the Middle and Upper Palaeolithic periods from regions which had not contributed to the formulation of the Out of Africa model or the Multi-regional model, especially from the Indian subcontinent and inland valleys of Arabia, Iran and Afghanistan, have in the last decade made tremendous impact on the timing of exit from Africa necessitating emphasis on the Middle Palaeolithic First model and therefore the ongoing competition between Middle Palaeolithic First and Upper Palaeolithic First models.

Archaeologists like Paul Mellars and Ofer Bar-Yosef argue that the modern humans entered India with typical Upper Palaeolithic tool kits comprised of blade technology and backed microliths, much as they did in Europe. Older dates for the microlithic in India have been published recently. This evidence from Central India is complimentary to the Microlithic First model and argue for a late entry of modern humans into India. There is no dearth of adherents to both these models and consequently the intensity of debate has increased over the last decade. Although there appears to be a compromise in respect of the route of dispersal out of Africa into South Asia and further east the issue being debated concerns with the attribution of capability as documented from the archaeological signatures, to either Mode III Middle Palaeolithic or Mode IV Upper Palaeolithic/Microlithic. The latter is assumed to have facilitated ease of adaptation to the „uniform‟ ecosystems across the old world coastline, especially to be able to consistently exploit marine food resources employing composite tools.

Understanding “Time depth and spatial organization of early Homo sapiens population substructure within Africa” is critical to explaining the origins of modern humans as well as generating the dispersal out of Africa model. The Middle Stone Age (280-30 Ka) of Africa is the time period of modern human origins and intra African dispersal on the one hand. The Out of Africa dispersal is placed in the time bracket between 130 and 75 Ka (MIS 5), coinciding with Late Pleistocene climatic amelioration that resulted in the formation of Green Sahara with a network of ecological corridors that led the hunter-gatherer Homo sapiens to the Eurasian gateway in the North of Africa. Though the origins of modern humans is placed in the Middle Stone Age of Africa, the time period of MIS 5 is generally accepted temporal span that witnessed widespread dispersal of Homo sapiens within and out of Africa. The Green Sahara model by integrating Archaeological, Palaeo-environmental and Palaeo-hydrological data has enabled delineation of spatio-temporal patterning of the Middle Stone Age lithic industries that have a bearing on identifying structure among Homo sapiens populations distributed across the region north of the Sahara.

Recently dated archaeological sites in Australia have provided new impetus to the debate on timing of the dispersal of modern humans out of Africa as well as the route(s) of dispersal in terms of southern route or northern route. The new dates for the Late Pleistocene (> 60 Kyr) occupation of Australia have advanced the entry by tens of thousands of years than what had been known till recently (~ 50 Kyr). The role of arid and coastal environments in facilitating the expansion is another aspect of this debate. Geographical areas with such prevailing environments during the various marine isotopic stages lie immediately outside Africa in Arabia, the Indian subcontinent and Australia. While several scholars are of the view arid geographical areas were a barrier obstructing ease of dispersal others envision the presence of desert oases that acted as dispersal corridors facilitating inland routes. Australia that was the destination of modern humans is the world‟s largest arid environment. It has more than 70% desert and the known early hominin sites are in the heart of this desert. Similarly the Arabian deserts, the Great Indian Desert (Thar) have well documented Pleistocene Palaeolithic sites. Presence of lakes, playas, springs (extinct and active), extinct rivers and dried up lakes are common to these environments. Despite Bio-geographical variation between and among them they, however, were hospitable environments to founder populations dispersing along either southern or northern route. Therefore it can be argued that „people came to the desert‟ rather than vice versa. Similarly a case has been made for the presence of refuge (core habitats) in the Indian subcontinent which remained unaltered despite climatic fluctuations during the Quaternary.

Central to this dispersal process debate is the nature of interaction between advancing modern humans and the native archaic human populations. There are two schools with diametrically opposing explanations: (a) Homo sapiens with their origins in Africa, around 200 Kyr, dispersed throughout the world replacing archaic populations (including Neanderthals) and; (b) in situ evolution of modern humans from their ancestral populations. The latter also known as Multiregional evolution argues for a single evolutionary lineage extending to 2 Myr and with variants; (a) one group suggests that modern humans evolved in Africa and then shared across the archaic populations through gene flow; (b) another group suggests that modern biological and behavioural traits appeared in different time and places. The 21st century debate, however, emphasizes the replacement interpretation.

If Africa occupies the place sui generis in human evolution it becomes inevitable to answer who were the first Africans to exit Africa, when and where the first colonization occurred and how many colonization events preceded the present distribution of human populations across the continents. Answer to this is revealed by a combination of evidence: (a) fossils, (b) material culture, (c) genetic foot prints, (d) Geo-chronology, (e) Palaeo-environmental contexts. A series of learned articles discussing the process of dispersals have taken an integrated view of these three sets of evidence from across the world. Interestingly only those areas which have produced robust body of evidence have figured in their discussion and the dispersal models thus generated are Eurocentric and envisage a short chronology for spread of AMH into Europe and rest of Asia and Australia through a single rapid dispersal. With the publication of new dates for the Middle Palaeolithic in Arabia and India, and colonization of Australia and the identification of Denisovans as a variant of modern humans the situation has changed. Although Arabia and India have not produced comparable sets of evidence their Late Pleistocene archaeological record supported by secure Geochronology have added a new dimension to modern human dispersal patterns. While several scholars have unwittingly extrapolated the Eurocentric model as the only logical way of explanation, with emphasis on Upper Palaeolithic/Late Stone Age revolution there is another school advocating Middle Palaeolithic/Middle Stone Age expansion into Arabia and further east into India and beyond, i.e. Australia.

In recent years genetic evidence, ancient mtDNA and Y-chromosome, has helped in better understanding of the evolution of Homo sapiens and Neanderthals as well as establishing the recent African origin for modern humans. The 1987 publication by Rebecca Cann et al.‟s represents a watershed in human evolutionary genetics and added a new pathway of research on human origins research. The last three decades mtDNA and Y-chromosome analysts have been intensively debating on African origin versus Multiregional evolution. On the basis of high resolution restriction mapping of mtDNA from 147 individuals from worldwide living populations put forth a strong case for locating the most recent common ancestor (MRCA) of world‟s living populations in Africa and used a molecular clock, mtDNA coalescence age, to date the time of the MRCA to between 140 and 290 Kyr. Accordingly the ancestor of the modern human maternal lineage had been African and lived relatively recently in the Late Pleistocene and left Africa between 13,000 and 180,000 years ago as opposed to the view that archaic modern human groups had dispersed out of Africa in the Middle Pleistocene. Although these findings have come under serious scrutiny over the last three decades it is now widely accepted that both the mtDNA and Y-chromosome have recent ancestry in Africa and had undergone prolonged evolution prior to dispersal from Africa.

Similarly extracted mtDNA from the Neanderthal specimen from Feldhofer Cave in Germany (dating between 40 and 50 Kyr) and comparison of its mtDNA sequence with the reference modern sequence revealed that divergence between modern humans and Neanderthals occurred between 690 and 500 Kyr, much earlier than the earlier estimate. Although this study also revealed genetic contribution from Neanderthals to modern humans (European) recent investigations have shown that there was interbreeding between and among them and that modern human DNA contains genes inherited from Neanderthals and Denisovans outside of Africa and the Melanesian population is found to contain Denisovan contribution.

5.1.The Green Sahara and Green Arabia: New Perspectives

In the context of modern human exodus from Africa three major Bio-geographical regions have been receiving increasing attention, during the decade and more, which were otherwise considered as major ecological barriers. Alternatively much research emphasized on southern dispersal route of Africa during the later Pleistocene, coinciding with the microlithic invention that facilitated exploitation of coastal resources all along their path till the northern shores of Australia. The new approach focusing on Green Sahara and Arabia on the basis of excellent Late Quaternary palaeoclimate records and newly discovered Palaeolithic sequences, dating from the Lower Palaeolithic, has identified the existence of ecological corridors across the Sahara and perennial Palaeolithic habitats supported by green biomass. This has given adequate importance to the Thar Desert of the Indian subcontinent that has been presenting uninterrupted human occupations from the Lower Palaeolithic onwards. That in these regions there prevailed intermittent sub-tropical environments during odd marine isotopic stages has been attested by palaeoclimatic proxy records. Increasing evidence of Late Pleistocene settlements, comprising Middle Stone Age assemblages, in all these regions are suggestive of strong modern human presence and dispersion along the inland ecological corridors of Green Sahara, Arabia and Thar. The Arabian evidence has helped in documenting the entire range of Palaeolithic cultures in the inland basins and exploding the myth that Arabia was bypassed by the dispersing human populations. Similarly the Indian subcontinent was considered a region cul de sac for human cultural evolutionary studies until the recent development of an absolute Geo-chronological timeframe for the Palaeolithic sequence in the Thar and other inland basins, the ever green Purnana-Gondwana Basins. This has necessitated a new paradigm for examining the potential routes of migration of hominins through the Sahara, Arabia, Thar to reach the inland basins of the Peninsular India, both during the Out of Africa I and II.

5.2. Evidence from Indian Subcontinent

In the subcontinent Archaeologists are confronted by the poor state of preservation of organic remains compelling reliance on Genetics and lithic assemblages from dated contexts, to be able to address issues relating to modern human entry into the region. The genetic evidence indicates modern humans likely left Africa 64-100 Kyr, but a wide range of different dates for first human entry into India are proposed by different genetic analyses, adding to this confusion. But for the hominin fossil records from Sri Lanka the paucity of fossil hominin records in the rest of the region has precluded the application of ancient mtDNA analysis and has constrained the sole dependence on dated lithic records from the subcontinent.

The rock shelter excavations at Jwalapuram (JWP 9) in Andhra Pradesh has revealed a sequence showing continuous development from the Middle to Upper Palaeolithic (microlithic) and the Central Indian (Vindhyan region) evidence from Mehtakheri is being interpreted as evidence of late entry of modern humans into India. As expected these regions present the beginning of microlithic technology (> 45 Kyr) much earlier than Jwalapuram (34 Kyr) and Site 55 in Pakistan is dated to 55 Kyr. The latter two sites are independent of precursor levels and therefore one needs to be cautious about the implications. This working hypothesis deserves attention as there are clear indications of co-occurrence of microlithic assemblages dating >40 Kyr in Central India and Middle Palaeolithic assemblages dating to pre-Toba in Rajasthan (older than 74 Kyr). Recent research in the large geographical areas of Arabia and India has been contributing in supporting Archaeological data coinciding with Oxygen isotopic stages 5-2. Scattered sites in India (Patne) Sri Lanka (Batadomba Lena) and Jwalapuram (JWP 9) have early and secure dates (>35,000 yr BP) for microliths of the „Upper Palaeolithic‟ or Mode 4 technology on the one hand and the sites of Jebel Faya (Arabia) and Jwalapuram (JWP 3/4) containing Middle Palaeolithic Mode 3 technologies on the other have dates coinciding with OIS  and YTT respectively (100-74,000 Kyr). Oxygen isotopic stages 5 and 3 interglacial climates were congenial periods, coterminous with a broad spectrum of food resources, but with high sea levels as of the Holocene.

The Jwalapuram lithic sequence has added stimulus to the ongoing Palaeolithic research in Arabia and to locating it at the cross road of hominin migration into the Indian subcontinent. The current documented evidence points to Arabia as the first stop of AMHs outside of Africa. The Aterian and Nubian assemblages, north of Sahara, and their occurrence in Arabia and beyond in the Indian subcontinent support an early expansion of AMHs out of Africa through northern routes. The presence of Aterian points in the Middle Palaeolithic assemblages has been noticed from early on. Presence of such projectile artefacts at a number of newly discovered Middle Palaeolithic assemblages is being documented as they are of great relevance in tracing the continental dispersal of early moderns into the subcontinent. The artefacts coming from distinctive geographical areas do reveal variation in terms of attributes owing to variation in lithic technology, the influence of raw material. This in turn needs to be viewed as showing patterning in space and time (founder effect) and how populations adapted to changing environments during dispersal.

Early on the dated Jwalapuram lithic sequence from the Kurnool sub-basin of the larger Cuddapah Proterozoic basin and uninterrupted human occupation despite the impact of YTT led to identifying similar perennial refuge habitats across the Deccan Plateau in the Indian subcontinent. The stratified and thus dated sites are as yet far and few between. The pre-Toba and immediate post-Toba assemblages are not associated with symbolic arterfacts, which appear rather late in the archaeological sequence at JWP9.

5.3. When did Modern Humans arrive in India?

The Southern Dispersal hypothesis, the Middle Palaeolithic First, the Upper Palaeolithic First and Microlithic model have given a prominent place for the Indian subcontinent in the debate on the origins and expansion of AMHs out of Africa. The region was otherwise considered peripheral to understanding the colonization processes that eventually led to peopling of the New World, Australia in particular around 60 Kyr. Assuming that any one of these models is correct the place of the subcontinent as the first stop of the AMHs outside of Africa will retain its current place. Between Southwest Asia and Australia the Indian subcontinent occupies a central place in the debate on out of Africa expansion of anatomically modern humans. The region has, however, microlithic sites dating back to at least 45, 000 years ago. A good record of later Pleistocene hominin fossil record is essential to be able to intensify the debate on colonization events associated with early AMHs out of Africa along a coastal route, that provide a central place to the coastline of India. The suggested beachcombing by the AMHs remains hypothetical in the absence of hard archaeological evidence even though the mtDNA coalescence dates lend support to this purported coastal route.

The presence of small bifaces (hand axes) in the Indian Middle Palaeolithic assemblages is considered to indicate in situ evolution of Middle Palaeolithic technologies outside Africa. Such industries are identified as Early Middle Palaeolithic or transitional industries. In India it is observed that quartzite Middle Palaeolithic assemblages are generally comprised of diminutive bifaces and heterogeneous core types, retouched flake scrapers, etc. At sites where limestone and crypto-crystalline silica material were utilized the percentage of bifaces is greatly reduced. In James (2007) analysis there is considerable regional variation in the Indian Middle Palaeolithic assemblages. The Levallois and discoidal preparation is common irrespective of rock material used. The Levallois technique is common in the Purnana–Gondwana basins. Outside these basin areas „unprepared and regularly flaked cores are common‟ suggesting that a variety of techniques were combined in different ways in different contexts. Although this situation is not intriguing, in the context of early expansion of AMHs out of Africa, the presence of small bifaces that are comparable to the Arabian Jebel Faya „C‟ assemblages in the Indian assemblages from the Purnana–Gondwana inland basins is of relevance to scrutinize the dispersal patterns, indicating the suitability of inland basins as well as transcontinental routes. That anatomically modern humans produce small bifaces is a significant point to be noted in the context of debate on the rise of Middle Palaeolithic as in situ development or replacement by AMHs.

The considerable regional variation in the Indian Middle Palaeolithic should be viewed as adaptive responses to the local habitat conditions instead of rejecting their authorship by and expanding single hominin groups i.e. AMHs. It is also argued that regional diversity in the Indian Middle Palaeolithic reflects gradual development of core technology from the Late Acheulian and at the same time agree that AMHs dispersed to South Asia using Middle Palaeolithic technology and not with the Upper Palaeolithic package.

6. Out of Africa III (80 -60 Kyr)

This period is thought to be the final and most successful dispersal event that led to peopling of Eurasia, Australia and the Americas. This dispersal event also witnessed replacement of archaic populations occupying Europe and parts of Asia. During this time period the northerly route from East Africa to Southwest Asia was blocked by severe arid conditions in the Sahara because of the onset of glacial conditions. It is suggested that some populations from East Africa dispersed into the Arabian Peninsula through the southern route along the Red Sea, from there they moved further into the eastern Mediterranean and further eastwards into India and Southeast Asia. This has been interpreted as a rapid dispersal event associated with coastal and estuarine environments. Evidence in support of this dispersal event is documented mtDNA analyses of aboriginal populations in South Asia, New Guinea and Australia. The mtDNA analysis of native Malaysian populations revealed the existence of two distinct lineages designated M21 and M22. These lineages are descendents of L3, H haplogroup ancestral to M and N lineages outside of Africa, while L3 is considered the founder lineage which first appeared in Africa around 86 Kyr. It has been observed that there is a short time gap between first appearance of L3 in Africa and its descendent M in South Asia (around 60 Kyr) which suggests a rapid single event dispersal expansion out of Africa along the southern coastal route. However, there is yet no unanimity among various scholars.

Colonisation of Australia around 60 Kyr is considered humanity‟s incredible feat, in a space of about 10,000 years the expansion of modern humans occurred between Africa and Australia, according to present DNA coalescent estimates. Similar rapid expansion along the circum Pacific route occurred leading to the first colonisation of the Americas, after 20,000 years ago.

7. Dispersal Routes Out of Africa

Geneticists and Archaeologists suggest two major routes out of Africa, one via Egypt and Sinai and another via Bab el Mandeb into Arabia and further east. The first one is known as northern route and the second one southern coastal route. These are considered gateways that facilitated hominin movement out of Africa during favourable climatic regimes, especially during the interglacial phases. Geographic, Palaeo-climatic, Archaeological and Genetic evidence have provided the basis for identifying these two exit routes. It is also suggested that when Sahara and the Nile Valley posed as ecological barriers the southern route facilitated the Bio-geographic movements between Africa and Eurasia. Existence of two other potential paths of dispersal are also under consideration: (a) through Central Sahara to North Africa and (b) along the western coastal margin of the Red Sea. This suggestion is based on the fact that events during interglacial periods of humid corridors existed through the Central Sahara, during 130-117 Kyr. The western coastal route along the Red Sea lies in proximity with Nile Corridor and this could have been useful for movement in response to climate changes. There is now a growing consensus among researchers that the southern route was most preferred to other routes, in light of ease of coastal adaptation and uniform and consistent availability of resources as well as hominin raft building capability and land bridges during low sea levels.

Conclusion

This chapter has introduced the current debates on the manner and circumstances leading to the peopling of the world first by anatomically ancients and later by anatomically moderns. Dispersal of human populations is a fact revealed by multiple sets of evidence. But the debate continues regarding the timing and routes of dispersal and the climate change impact on the movements. The nature and distribution of Archaeological evidence in distinctive geographical environments reveals the first major expansion took place in a network of continental areas designated Old World. The colonisation of new land masses by rapidly dispersing modern humans led to colonisation of Australia and the Americas i.e. the New World. Archaeological research helps reconstruct the history of human settlements in each of the distinctive regions of the world.

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