Turkana Basin Institute

Two exciting new hominin fossils discovered at Ileret, a remote region east of Lake Turkana, have shed new light on the origins of the human genus Homo. The fossils were discovered by an international team of scientists which included several Turkana Basin Institute researchers. In August, the report of these fossils made the cover of the prestigious scientific journal Nature.

An established view of human evolution posits that three species evolved, more or less, one into the other: Homo habilis, Homo erectus, and Homo sapiens. However, the new fossils from Ileret challenge this linear view of human evolution over the past two million years.

One of the fossils is an upper jaw bone of Homo habilis which dates to roughly 1.4 million years ago, making it the most recent fossil of this species yet discovered. Such a recent date demonstrates that Homo habilis and Homo erectus co-existed in eastern Africa for nearly half a million years, making it very unlikely that the two species share an ancestor-descendent relationship. “The fact that they stayed separate as individual species for a long time suggests that they had their own ecological niche, thus avoiding direct competition”, suggests Meave Leakey, Turkana Basin Institute researcher and one of the lead authors on the paper.

The second fossil is an extraordinarily preserved skull of Homo erectus, dated to roughly 1.5 million years ago. The skull was first discovered in 2000 by Turkana Basin Institute Postdoctoral Fellow, Fredrick Kyalo Manthi. The fascinating feature of this find is its small size. In fact, the fossil is the smallest Homo erectus specimen known from anywhere in the world. The inclusion of this fossil within Homo erectus expands the know size variation of this species to that see between male and female gorillas. Thus, the variation documented in Homo erectus may suggest that this species was highly sexually dimorphic compared to modern humans. If this is the case, Homo erectus may be less modern than previously thought.

For further information, see:

http://www.nature.com/nature/journal/v448/n7154/abs/nature05986.html

http://www.kfrp.com/media/index.htm

http://www.grad.sunysb.edu/newsletter/Linear%20Evolution.htm