Tiny Indonesian hominids get the SciAm treatment

The tiny adult remains of Homo floresiensis reported in 2004 (see The little people of Flores, Indonesia, November 2004 issue of EPN) astonished the palaeoanthropological community more than any discovery since René Dubois’ found the first H. erectus remains on nearby Java almost a century ago.  Their recent geological age (about 13 ka), together with evidence for cohabiting the island of  Flores with fully modern humans and legends of the ebu gogo – “the grandmother who eats anything” spice up the find no end.  So it is not surprising that Scientific American has commissioned an excellent popularised account of where things stand with the little people only a few months after the discovery was announced in Nature (Wong, K. 2005.  The littlest human.  Scientific American February 2005 issue, p. 40-49).  It is not just the sheer tinyness of Homo floresiensis that draws our attention, but the fact that with a brain no larger than 2 Ma old australopithecines, the species crafted tools that are far more sophisticated than those of their most likely ancestor, H. erectus.  They also found their way across a seaway that could never have dried out during glacial maxima, used fire, and just as important survived competition with fully modern humans for around 20 ka.  Yet, as the article is at pains to point out, the find is so new that it is easy for specialists to kid themselves into believing a great deal more than may eventually turn out to be likely.  With two cultures on one small island, there may well have been mixing of artefacts, and also occupation of the site – a large cave – by both over the long period when they shared the island.  Opinion of many leading figures in the field is related by Kate Wong, and it is very clear that there is a lot of puzzlement.

The oldest modern humans

For a long time it has been known that the “front line” between fully modern humans and European Neanderthals was in the Middle East, with fluctuating occupation of highly productive sites since around 100 ka.  It is also well established that the ancestors of all of us outside Africa began to migrate some 70 to 80 thousand years ago, the signs being that the pressure was drying of the continent as global climate cooled.  The route take is not at all well defined, but one possibility is across the Straits of Bab el Mandab at the entrance to the Red Sea as islands became exposed when sea level began to fall.  So, fully modern humans originated in Africa, but where and when?  Unsurprisingly because of the intensity of research there since the discovery of Lucy, the Afar Depression of Ethiopia has provided most remains of H. sapiens sapiens.  Volcanic ash layers in sediments that contain specimens there give ages up to about 160 ka.  But Ethiopia has other hominid-rich sequences, including ones that have yielded anatomically modern humans.  The most notable is the Late Pleistocene Kibish Formation of the Omo River basin in southern Ethiopia, a deltaic sequence that formed when Lake Turkana had higher levels.  Human remains occur in the lower part of the Kibish Formation, and as luck would have it, they occur between two volcanic ash horizons and can be accurately dated (McDougall, I et al. 2005.  Stratigraphic placement and age of modern humans from Kibish, Ethiopia.  Nature, v. 433, p. 733-736).  For the moment, they are the oldest proper humans at 195 ka.  That age has interesting connotations as regards the climatic conditions of their lives.  The Omo basin shares watersheds with drainages into the Blue and White Nile system.  At 195 ka increased deposition of organic matter characterised the sediments beneath the Nile delta, which suggests greatly increased rainfall in the uppermost reaches of the Nile system.  That coincides with the onset of deposition of the Kibish Formation when Lake Turkana stood much higher than at present.  The area would have been lush.

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