Endeavours to trace the expansion of Homo Sapiens from Africa to Island SE Asia and Australia traditionally commence in Africa/SW Asia. There are a number of aspects, which are associated with these dispersals, that have not been resolved. This article briefly reviews the current status of pertinent eastern archaeological investigations and their relationship to recent genetic studies, which might have an influence on the chronology of eastward migrations from SW Asia.
A human third metatarsal was recovered from Callao cave on the northern Philippine Island of Luzon. The fossil has been directly dated by U-series ablation, which yielded a minimum age of 66.7 +/-1.0Ka and which is compatible with the ESR age determinations. The morphological features, size and shape indicate, that metatarsal definitely belonged to a small Homo sapiens. Since there is a paucity of Homo erectus and Upper Pleistocene human foot bones in SE Asia, the Callao fossil was compared to the Philippine Negrito MT3. The Negrito occupied the regions of Luzon proximal too the cave. The anatomical comparisons indicate that the Callao metatarsal largely falls within the Negrito range, with a few minor divergences [eg; the medial facet of the second metatarsal appears to be more plantarly oriented, than is generally encountered in Homo sapiens]. Although there is evidence that animals were butchered at the cave, no lithic implements were recovered [A Mijares,2010].
The Luijiang fossils were retrieved from a small cave at Tangtionya, Gangxi, in southern China.. The skull was extracted from a debris flow, that was covered by calcite ca 67 +/-5.0Ka [U-series measurement]. Age estimates below the calcite flow range up to 135Ka. Luijiang, who might have been a young male [?] had a modern cranium, with robust post cranial bones and was classified as a modern human [S Guanjuan,2002]. The non-pragnathic , flat face has midline kneeling and an occipital with affinities to Jinniushan. Luijiang's modern characteristics are a non-prognathic, flat face, low nasal angle and shovelling of the lateral incisors [Wolpoff,1999].
There are volcanic tuffs in the Jwalapuram River Valley of southern India, which were emplaced during the eruptions from Toba. Electronpoebe microanalysis of obsidian from Jwalapuram locality 3 tephra, identified a 2.55m ash deposit from the ca 74KA Toba volcanic eruption, with under and overlying lithic tool assemblages. Optical measurements for the two cultural horizons provided ages of 74 +/-7 and 77+/-6Ka. Typologically similar blades, burins and various scrapers occur above and below the Toba tuff. A Chi square test of variations in the preparations basic classes of lithic materials did not reveal any major variations in the pre- and post-Toba preparations component. T tests of the size, shape and technological features of the tools yielded similar results. Discriminant cores "unambiguously" cluster with those of thirty, broadly coeval Middle Stone Age African sites. Production of uni- and bi-directional flaked cores, with high rates of elongated scars, which implies high rates of blade production, faceted platforms and largely cortical blanks provides the strong resemblance [M Petraglia,2007].
B Pedra [2009] found lithic axes, cleavers and scrapers at Barpadar village on the Upper Jira River of the Bargarah district, Orissa, India, which provisionally date to 70Ka or earlier. These tools share some characteristics with contemporary assemblages in a number of east African areas [ibid]. No human remains have been discovered at the above sites to provide the identity of the stone implement makers. The apparent occurrence of Homo sapiens remains at Luijiang, China, and Callao Cave, Luzon, which tentatively date to ca 67Ka, and the reported similarities with Middle Stone Age lithic tools at east African sites, could imply that Homo sapiens had reached the subcontinent, when Toba erupted.
Field work in the southern Huon Peninsula of SE Papua New Guinea unearthed charcoal samples at the AAXF Vilakuov site, that date to 45.5 +/-1.57Ka,cal. There are no earlier diagnostic indications of Homo sapiens on New Guinea. The stone tools are rudimentary [G Summerhayes,2010].New Guinea highlanders are the least diluted of the ancient populations that lived on the Sahul continent. They had robust features, heavy bones and strong supra-orbital ridges. They shared some morphological characteristics with the Qafesh/Skhul human remains in Israel.
The Carpenters Gap in the central south Kimberley region of NW Australia was initially utilized ca 46.3 +/-1.4Ka [cal; S OConnor,2001]. Devil's Lair near the SW extremity of the continent contained a hearth that is ca 44.9 +/- 0.95 Ka [cal.] old. The deeper cultural horizons 31-38 were subjected to considerable post-depositional disturbance and there is no reliable chronology for the sedimentary section. G Turney [2001] speculated, that Devil's Lair might have been utilized by hunter-gatherers as early as 47Ka. There is a remote possibility that the Nauwalobila and Malakunanja rock shelters in Arnhem Land were visited by foragers pre-50Ka, but the chronologies at the two sites are highly tenuous. The Carpenters Gap site provides the earliest reliable evidence of a human presence in Australia. Since it is located a considerable distance inland from the northern coast line of Sahul, the first Australians arrived at an earlier date.
Their initial stone tools belonged to the core tool and scraper tradition. These implements vary regionally and do not bear a strong technological similarity to Middle Stone Age artifact assemblages in east Africa. The latter industries were characterized by points, that were produced by using a faconnage technique, and a range of flake tools, that were made from Levallois and blade cores. The lithic technologies at Jwalapuran locality site 3 and the Baradar village site, India, also vary from the early stone tool kits in Australia and New Guinea. There appears to have been a considerable hiatus between Homo sapiens colonizing India/China and Australia/New Guinea. Although mtDNA macro-haplogroup [hg] M lineages tend to be prevalent in eastern Asia, the most frequent hg in Australia belongs to macro-hg N. Hg S and its descendant lineages are the most common on the island continent [Kivisild,2005].
A Merriwether [2005] obtained the entire mtDNA sequences for 14 North Island Melanesians and identified three new branches of macro-hg M, which are not related. They are M27,M28 and M29.Their average coalescence ages are estimated to be 73.5 +/-7.4Ka,which is appreciably earlier than previous estimates.The latter were not based on entire mtDNA sequences. These three unique variants appear to have diverged prior to the colonization of North Island Melanesia [ibid].The mean coalescence age is compatible with discovery of the ca 67Ka Luijiang and Callao 1 Homo sapiens fossils.
C Hill [2006] sampled the high resolution mtDNa coding and control regions, which were obtained from complete sequence data, for 928 individuals from Island SE Asia and Formosa. Nearly 14% of the Island SE Asia specimens, which have not been observed outside the region, belong to macro-hg M. Their origins probably trace back to the early colonists. All the ancient SE Asian lineages seem to be distantly related and share a common root ca 58 +/- 13Ka or earlier [ibid].
J Trejaut [2011] analysed 400 mtDNA samples from Borneo, Sumatra, Sulawesi, Java and a few eastern Indonesians. Ca 14% of these individuals harboured non-interconnected, deep rooted lineages, which are descended from macro-hg M and which appear to have been isolated for a long time. These archaic female lineages bear a similar relationship to macro-hg M as the Andamanese M31 and M32, Philippine M71 and M73, Melanesian M27, M28 and M29, and Malaysian M21 and M23 lineages do. Additional complete sequencing of these deep rooted lineages resulted in the identification of more than 26 macro-hg M and 6 macro-hg N basal genetic lineages, that had not been defined. They [ca 50-46Ka]could represent an archaic Sundaland gene pool [ibid].
E Gunnarsdottir [2011] used high through put sequencing platforms to generate 109 complete sequences for three Filipino groups, which included the Mamanwa Negrito. A total of 22hgs were recorded, which were equally distributed between macro-hgs M and N. Two new hgs were identified and were provisionally designated as M* and N* Hg N* has a 36% presence among the Mamanwa specimens and is minimal or absent among the other two groups. The estimated divergence of N* ranges from 72.5-44Ka ago. The Mamanwa appear to have been largely isolated from the other two populations, since the time of divergence. Hg N* might [?] represent a founding lineage. Macro-hg N lineages have a similar frequency among native Australians [ibid].
Complete sequencing of mtDNA samples continues to identify more ancient lineages in Island SE Asia and provide earlier coalescence ages. The increase in ancient diversity implies an earlier age for colonization, than was originally estimated.
Hi Shi [2008]analysed 5134 Y chromosome samples from 73 east Asian populations and from YAP+ published data to reconstruct the phylogeography ot the D-M174 lineage. He estimated a coalescence age of 66.4 +/-1.47Ka for D-m174, which exhibited a deep diversion between north and south east Asian populations. The distribution pattern varies from most other East Asian specific lineages and it has a mean 9.6% frequency among the populations. This includes Andaman Islanders 56.25%, Tibetans and Japanese 30-40% and southern Chinese ca 30%. D-M174 is more prevalent in the peripheral regions of east Asia. It appears to be one of the oldest lineages in east Asia with northward expansion possibly occurring as early as 60Ka ago [ibid]. Y chromosome hg Mi68 was the first "surviving" hg to leave Africa. Hg 130 evolved en route to Australia, where it currently has a 60% frequency.
Since Homo sapiens and Neanderthals diverged pre-350Ka, a number of derived alleles present in the Neanderthal DNA can be expected to segregate in all human populations. Segments of human DNA, that are subsequently admixed outside of Africa should carry additional derived alleles, that are shared with Neanderthals and are absent among sub-Sahara Africans. The Dye 44 polmorphisms for a worldwide sample of the 6092x chromosome were analysed. Structurally distinct haplotype B006 , with only four derived alleles , is common outside of Africa and is virtually absent in sub-Sahara Africa. African B006 occurrences are deemed to be the result of gene flow from outside Africa. The derived allele G ofrs 11795471 is unique to B006.It harbours two types of derived alleles, that are shared with Neanderthal DNA at frequencies of 7.5% or higher. The includes the first Australians, whose ancestors migrated eastward to the island continent after admixture with the Neanderthals [V Yotova,2011],
The distal manual phalanx of a hominid fifth digit [50-30Ka old] was retrieved from Denisova cave in the northern Altai Mountains of Russia. MtDNA genetic studies by J Krause [2010] established that the Denisovan individual was not a Neanderthal or Homo sapiens. The nuclear genome was sequenced from the Denisovan finger to ascertain its relationship to extant humans and Neanderthals [D Reish,2010]. On average the Denisova genome shares a more recent ancestor with Neanderthals than it does with Homo sapiens. A comparison between Denisova and a present day Melanesian specimen revealed that they shared 4+/-0.7% alleles that Melanesians do not share with Neanderthals [ibid].Admixture between the Melanesian's distant ancestors and Denisovans probably occurred before this particular Melanesian lineage entered Melanesians.
No genetic comparisons were made with indigenous Australians. Analysis of 38 genetic SNP specimens from the inland Riverina district of Australia revealed, that Australians clustered with Melanesians and New Guineans a long time ago and had subsequently diverged. They all share a common, distant ancestry [B McEvoy,2010].
Collation of the above suggests that Homo sapiens reached the subcontinent marginally before the ca 74Ka Toba volcanic eruption. This spectulative premise is based on a growing volume of circumstantial evidence. Whether the descendants of Qafzeh/Skhul or Jebel Faya Homo sapiens made any contribution to this initial gene pool is conjectural. More genetic data is required to establish whether Denisovans ever inhabited the subcontinent.
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