In 1985, a cranium was found by Alan Walker at the west side of Lake Turkana in Northern Tanzania and was named Australopithecus aethiopicus. The cranium was as robust as any yet known, but was 2.5 million years old. Clearly, the huge molars, flared cheek bones, and dished face could not be the end-product of an evolutionary line if it were present at the origin of that supposed line. How this discovery affects the shape of the hominie family tree remains under discussion today.

This cranium, known locally as the "black skull", was surprising not only because of its great age but also because it contained an unexpected combination of anatomical characteristics. Although the face was distinctly like that of that most robust of robust australopithecines, Australopithecus boisei, the cranium � particularly the top and back � was not: it was similar to that of Australopithecus afarensis. Such an anatomical combination surprised most people, and reminded us that hominine biology of 3 to 2 million years ago was more complicated than current hypotheses have allowed.

Reference: Walker A. et al. 2.5-Myr Australopithecus boisei from west of Lake Turkana, Kenya. Nature 1986, 322: p. 517-522.