A publication of the Archaeological Institute of America
A 3.0- to 3.5-million-year-old australopithecine jaw discovered in the Central African nation of Chad has prompted a reassessment of early hominid evolution. Found by French paleoanthropologist Michel Brunet of the University of Poitiers at a site near Koro Toro, the fossilized jaw and seven remaining teeth resemble those of Australopithecus afarensis, a species known from the East African sites of Hadar in Ethiopia and Laetoli in Tanzania. The new find is the first australopithecine discovered west of the Rift Valley. Paleoanthropologists have long thought that when East Africa's Rift Valley formed during the late Miocene, some five to seven million years ago, it functioned as a geographical barrier separating ape populations. Those in open grasslands, it was believed, were under more pressure to abandon their arboreal way of life in order to survive, thus initiating hominid development. "We now know that this is far too simplistic a scenario," says Harvard University paleoanthropologist David Pilbeam. "Although climate change is a more likely factor, we simply have too little data to explain such a singular event in human history."
Paleontologists also recovered the fossilized remains of grassland animals including rhinoceros, giraffe, and horse, as well as those of pigs and elephants, more woodland species, suggesting a mixed environment rather than the savanna of East Africa. "Now that we have australopithecines all over the continent," says Brunet, "it will be impossible to determine their precise place of origin. What we now know is that the Rift Valley was not the only cradle of humankind." The find is sure to focus more attention on Central and West Africa as potential hotspots for hominid research.