National Geographic : 1995 Sep
More clues to hominid development Like a primordial grin from across the eons, a 4. -million-year-old jaw bone delights the author (right) moments after it was discovered at Kanapoi by a member of the fossil-hunting team called the Hominid Gang. Both this mandible (above, at left) and an upper jaw, or maxilla, with protruding teeth that was found nearby are significant discover ies-though a complete skeleton remains the ultimate goal. Before the 1994 season there was scant evidence of homi nids older than 3.6 mil lion years. The Kanapoi mandible proved more "chinless" and thus more apelike than specimens of Aus tralopithecus afarensis. But the teeth tell us that this primate was a homi nid, not an ape. The ver tically placed root of the heavily worn canine in the upper jaw (inset, facing page) isclearly more humanlike than the angled root in chimps. Such differences lead Leakey to believe that she has discovered a new species. Several fragments from Lake Turkana's Turkwel site turned out to be carpal bones from a hominid 3.5 million years old. One of these-a hamate bone-provides a valuable clue for infer ring the creature's hand strength. As illustrated at far left, the wrist bones form a "carpal tunnel" through which tendons pass from the arm mus cles to the fingers. Be cause the hook of the Turkwel hamate is about twice the size of that in modern humans, Leakey reckons that the tunnel was deeper, holding larger tendons for stron ger hands. This supports the thesis that early hominids were still heavily engaged in tree climbing.