Message from Dr. Leakey


In 1925, the South African anatomist Raymond Dart shocked the world when he announced the discovery of a fossil skull of a young primate he called Australopithecus africanus. Dart’s claim, that this "Taung child" was a human ancestor, flew in the face of current views that human evolution occurred in Asia and Europe and was rejected by much of the scientific establishment at the time. Subsequent discoveries by Dart and the South African paleontologist Robert Broom clearly established that Australopithecus was indeed a fossil hominid, and like us, it walked on two legs.

Beginning in 1959, Louis and Mary Leakey discovered other fossil hominids at Olduvai Gorge in Tanzania and firmly established Africa as the center of early hominid evolution, as Darwin had reasoned 100 years before.

Expeditions by my family and myself in the Turkana Basin of Kenya beginning in 1968, and by other scientists from all over the world in other parts of Africa, have continued to expand our understanding of the diversity of early hominids in the Pliocene and Pleistocene of Africa. However, among the early hominids of Africa, Australopithecus stands out as both the best known, in the number of fossils recovered and the number of different species that have been assigned to this genus, and the most confusing because of all the questions raised by this abundance of information.

The subject of the 2007 Stony Brook Human Evolution Workshop is Diversity in Australopithecus. This genus is the most geographically widespread and taxonomically diverse hominid in the Pliocene of Africa with Australopithecus africanus in South Africa, Australopithecus afarensis in Tanzania and Ethiopia, Australopithecus anamensis in Kenya, Australopithecus garhi in Ethiopia, and Australopithecus bahrelghazali in Chad. In time, these range from A. anamensis at more than 4 million years old to A. garhi at 2.6 mya. The evolutionary relationships among these different species have been the subject of ongoing debate for a quarter of a century. How are all these species related? And how are they related to other early hominids, including our own genus Homo? What factors are responsible for this diversity? Is the observed variation across species a product of anagenic change through time of a single lineage? Or is it the result of geographical separation or adaptation to different ecological habitats?

The adaptations and behavior of Australopithecus are also a source of ongoing debate. While most scientists agree that these early hominids were bipeds, as eloquently demonstrated by the footprints from Laetoli, Tanzania, they show many features not found in living humans such as relatively long arms, and long curved toes and fingers suggesting they were also at home in the trees. New techniques provide insight into the diet of these early hominids, and studies of morphological diversity within species suggest considerable sexual dimorphism in body size.

Finally, there are several fossils of young individuals, including an exciting new skeleton from Ethiopia, that together with studies of tooth development offer insights into the life history of these early hominids. How did their rates of growth and maturation compare with later hominids? Did their brains grow quickly like those of apes, or did brain growth extend into childhood as in modern humans? Did their locomotor behavior change with age?

We have much to talk about and even more to learn regarding Australopithecus and its place in human evolution. Thank you for joining us for the Fourth Annual Stony Brook Human Evolution Symposium and Workshop.

 

 

Richard Leakey, Professor
Stony Brook University