It was in the year yuvan, which we were passing through for the first time in our life, when skanda freed us from the vile dasyu who was tailing us for a while. In the city of the great dancers our eyes fell upon a remarkable paper on the library racks – the upper Semliki valley harpoons of Zaire (today DR of Congo). Having read it and made some notes we stumbled out taking a eastern route through the wooded track. ST joined us but we were so engrossed in the thought of what we had read that we did not converse with her for a while. What so striking about all this?
For a while it had been supposed that anatomically modern Homo sapiens appeared in Africa sometime between 130-100 Kya. Between 130-60 Kya Africa is dominated by what are known as Middle Stone Age (MSA) technologies. By around 40 Kya there is a notable technological shift observed in certain parts of Africa, with a new microlithic technologies, the preparation of bone tools and the use of ostrich eggshell beads (something still used by the bushmen of the Kalahari). These technologies are termed the Later Stone Age (LSA). In western Eurasia and Central Asia we see the middle Paleolithic Mousterian stone tool technology dominate till around 35 Kya. Here, somewhere between 40-30 Kya we see the emergence of the prismatic blade cores, bone and horn tools, advanced fire places, ornaments, and symbolic art. By 30 Kya these features start dominating, marking the transition to the late Paleolithic. At least in West Asia and Europe this transition seems to have been coeval with the rise of Homo sapiens and the decline of Homo neanderthalensis. In India the situation is very murky due to limited data. However, we know that around 80-70 Kya we have MSA technologies resembling those seen in Africa. It is believed that in India from around 30 Kya a gradual replacement of MSA technologies with more LSA-like technologies happened as opposed to the more abrupt transitions elsewhere (However, this contention is based on limited data). It was against this background that the Semliki valley bone harpoons were striking – they were dated to around 90 Kya, squarely within the African MSA. Such barbed weapons were to be found in Ishango in DR of Congo and also Tsodilo Hills in Botswana only 60 Kys later. In Europe such barbed tools are only 14 Ky old. Thus, despite anatomically modern Homo sapiens apparently existing in Africa by the time of these tools, nothing comparable to this type of tool-making is seen in Africa or elsewhere for a long. So here we have an unusually precocious record of modernity from the MSA of Africa, which does not temporally correlate the emergence of advanced technology elsewhere.
The related harpoons from more than 60 Kys later (thus a LSA site from ~26 Kya), found at Ishango, DR of Congo, in the same general region of Africa, points to a certain continuity with the earlier MSA technology over a rather long period of time. Along with these tools de Heinzelin recovered remains belonging to at least 9 humans – while rather fragmentary there are some well-preserved mandibles, femora and other bones. A recent study of these bones, so far only reported in abstract form, finds evidence for archaic features in them, i.e. morphological elements typical of representatives of Homo prior anatomically modern H.sapiens (AMHs). Thus, as late as 26 Kya we still have evidence for possible inter-breeding between more archaic Homo coexisting with AMHs. While this report is still preliminary, we have a rather well-worked out study by Stringer, Harvati and colleagues that looks at the LSA remains dating to about 11-16 Kya from Iwo Eleru, Nigeria. This partial skeleton, includes a calvaria, mandible and fragmentary postcranial remains and is accompanied by LSA artefacts and charcoal dating to 11.2 Kya (consistent with the bone’s date). Strikingly, the calvaria of this individual had features that resembled archaic fossil Homo represented by skulls such as Omo1/2 (195-200 Kya, Ethiopia), Saccopastore 1 a primitive Neanderthal-like skull (100-130 Kya, Italy) and Ngandong, i.e. the Solo man or a Homo erectus-like skull (>143 Kya, Java). A principal component analysis of calvarial landmarks including the Iwo Eleru human shows that it groups outside the cluster of modern and almost all Upper Paleolithic humans and shows affinities with Homo heidelbergensis and Homo neanderthalensis. Thus, it is rather notable that as late as 11-12 Kya in Southern Nigeria there were individuals who still retained archaic features that were present in representatives of Homo more than 150,000 years before that time. This is the remarkable archaism of Africa that appears to go alongside with the precocious modernity note above. For a while we have felt that in the vast continent of Africa there should be signs of interbreeding between Homo of archaic and modern aspect resulting in hybrid morphologies. These remains do seem to point in that direction and suggest that the so called AMHs and archaic Homo have been diverging and them merging again, never fully isolated from each other.
A few days ago Mendez et al reported a remarkable finding. A deceased African-American from South Carolina had submitted his DNA for genealogical studies. Surprisingly, his Y chromosome displayed the ancestral state for all known Y chromosome single nucleotide polymorphism. Further analysis showed that his Y chromosome was well outside of all the previously known human chromosome, including the extremely early branching ones of the Bushmen of Southern Africa. An estimate of the age of divergence of this Y chromosome from the rest of the human males showed that it was 338 Kya (95% confidence interval 237–581 Kya). This is well beyond the age of any thing which has been considered AMHs! Interestingly, this African-American was not alone in having this Y-chromosome. Further investigations by the authors showed that related Y-chromosomes could be seen in multiple males among the Mbo people of Cameroon not far from the Nigerian border.
Continued…
Filed under: Scientific ramblings Tagged: Africa, Archaic Homo sapiens, Neanderthals, Stone Age
