Hominins took refuge in northern Chad? – The Biogeography of Australopithecus bahrelghazali revisited

One very important but ultimately difficult question is What evidence is there for the movement of hominins? We have fossil hominin remains but most of the time the scarcity of these mean that we have to look elsewhere. Alot of biogeographical studies now look to other contemporaneous fauna that lived at the same time, after all there are more surviving remains of ancient elephants than hominins and as a result they can shed some light on the movement of hominins. There are occasions where the fossil hominin remains themselves can shed some light on their movements, by understanding their diet.

Australopithecus bahrelghazali was uncovered in northern Chad in the mid-1990s. Now considered by most palaeoanthropologists to be Australopithecus afarensis, this individual lived about 3.5 million years ago in a different world to the one we are familiar with today. Gabriele Macho of the University of Oxford, UK attempted to revisit the KT 12/H1 fossil. Macho argues that the evidence she has examined suggests Au. bahrelghazali migrated to and lived in a refugium at Koro Toro, northern Chad.

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KT 12/H1 – Holotype of Au. bahrelghazali

There is one difference that exists between Au. bahrelghazali and Au. afarensis and that lies in enamel thickness of the teeth. With an intermediate to thin grade of thickness, Au. bahrelghazali is thinner than that of Au. afarensis. This hominin is likely to have subsisted on sedges, which are superficially like grasses but with a different internal structure. As the climate in north central Africa became dryer, species that relied on sedges were squeezed into smaller areas called refugia, with bodies of water. Around 3.9 million years ago, climatic records show a gradual aridification of Africa and it seems plausible that that Au. afarensis made it way as far west as Chad, before becoming isolated and adapting to changing conditions, i.e. enamel thickness reduced.

Check out the article here:

http://www.sciencedirect.com/science/article/pii/S004724841500161X

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