A 3.5-million-year-old skull is a baffling mosaic of primitive and advanced features.
Hot on the heels of the controversial Kenyan fossil Orrorin tugenensis1, claimed to take the human lineage back to around 6 million years ago, comes a spectacular new find from Meave Leakey of the National Museums of Kenya and her colleagues2.
The new discovery from the famous Leakey stable will blur the already murky picture of man's distant past. The find is a battered but almost complete skull and face of an entirely new breed of early human.
The researchers call it Kenyanthropus platyops -- The Flat-Faced Man of Kenya. It comes from a rugged, semi-desert site on the western shore of Lake Turkana in northern Kenya.
The most striking thing about this face is how human it looks. It appears very similar to a fossil discovered in the 1970s on the eastern shore of Lake Turkana -- a skull almost universally known by its catalogue number, KNM-ER 1470. Apart from having had a rather small brain, '1470 Man' had a very human-like face -- flat, rather than protruding like an ape, and with small teeth.
The precise age of 1470 Man was controversial for some years. It is now thought to be around 1.8 million years old, and is assigned to the species Homo rudolfensis -- generally regarded as a very primitive member of our own lineage.
But at 3.5 million years old, the Kenyanthropus platyops skull is almost twice as old as 1470 Man. That it is as antique as primitive forms such as Australopithecus afarensis (popularly known as 'Lucy') threatens to double the antiquity of the human lineage at a stroke.
Closer inspection, however, shows Kenyanthropus to have a mixture of advanced and primitive features. For example, its small ear canal is more like that of chimpanzees and the very primitive members of the human lineage that lived in East Africa just over 4 million years ago (Australopithecus anamensis and Ardipithecus ramidus). Indeed, in some respects Kenyanthropus is more primitive than Lucy.
All of which suggests that a flat, human-like face appeared early in evolution alongside a range of other facial forms, and was not the outcome of the kind of progressive, linear evolutionary development popularly imagined.
Senut,B., Pickford, M., Gommery, D., Mein, P., Cheboi, C and Coppens, Y. First hominid from the Miocene (Lukeino formation, Kenya) C. R. Acad. Sci., Paris 332, 137 - 144 2001.
Leakey,M. G., Spoor, F., Brown, F. H., Gathogo, P. N., Kiarie, C., Leakey, L. N. and McDougall, I. New hominin genus from eastern Africa shows diverse middle Pliocene lineages Nature 410, 433 - 440 2001.
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Gee, H. New hominid skull. Nature (2001). https://doi.org/10.1038/news010322-8