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Texas State scientist adds to evolution understanding

By Ann Friou

Posted by University News Service

Sept. 4, 2012

Excavation of an ancient bone bed at Cornelia, South Africa, near Johannesburg, recently uncovered a human molar and stone tools dating to about 1 million years ago, leading scientists a step closer to understanding human evolution.

The excavation was led by James Brink, head of the Florisbad Quaternary Research Department at the National Museum in Bloemfontein, South Africa. Britt Bousman of the Anthropology Department at Texas State University-San Marcos, dated the site in collaboration with Andy Herries of Australia’s La Trobe University, using a technique called paleomagnetism.

The molar, according to Jacopo Moggi-Cecchi from the Universitá di Firenze in Italy, is the oldest human remains to be discovered in South Africa’s Free State Province, and is either that of a Homo erectus or perhaps the more primitive Homo habilis. 

The discovery of the 1 million-year-old site is significant, Bousman said, because so little is known of early humans between 1.5 million and 200,000 years ago. Brink added that, if this tooth is confirmed as Homo habilis, then it is the youngest Homo habilis remains in Africa, showing that the evolution of hominines is more complex than is currently understood.

“In southern Africa, we have well-preserved human remains from 4.5 million to about 1.5 million years ago, from Australopithecines, who ate plants and scavenged animal carcasses.  But, once hominines such as Homo habilis and Homo erectus started making stone tools and shifted to hunting, the archaeological record thins out in southern Africa. We have huge gaps of missing information between 1.5 million and 200,000 years ago. This finding helps us to fill in the record,” Bousman said.

Bousman was the first archaeologist to date the Cornelia site using paleomagnetic reversals, and the molar is the oldest hominine specimen to be found in southern Africa, outside of the so-called Australopithecine caves in northern South Africa.

The molar and stone tools—found in a bone bed probably created by spotted hyenas—were discovered by James Brink and his international team of archaeologists and other scientists—including Bousman—from South Africa, Australia, Great Britain, France, Italy, and the United States. Details of the discovery were published recently in the Journal of Human Evolution, www.journals.elsevier.com/journal-of-human-evolution.

The stone tools include large hand axes and cleavers, for butchering animals and crushing bones. These tools stand out for their great size, according to John Gowlett from the University of Liverpool. The hand axes measure about 9.5 inches long and the cleavers measure over 7 inches long, 4 inches wide and more than 2 inches thick.

Hand axes of this length are known from many sites in Africa, but it is unusual for them to predominate in an assemblage, according to Gowlett.  Stone flakes and other tool-making debris were also discovered in the bone bed, suggesting that these and similar tools had been made close to the spot.

It is believed that individuals classified as early Homo hunted by running their prey—including wildebeest, eland, an extinct giant wildebeest called Megalotragus eucornutus, and other antelope—to exhaustion.  Because the stone butchering tools were very heavy, early humans probably worked cooperatively to steer their prey—sometimes whole herds of animals—toward a killing site where they used these tools for butchering.

Bousman has conducted archaeological studies in South Africa since the 1970s, studying the physical, environmental, and behavioral changes that catalyzed the dispersal of modern humans.  “Being able to date the human remains at Cornelia to 1 million years ago has been perhaps the most exciting experience of my career,” he said.

Bousman, who also studies Paleoindian and Archaic archaeology in the U.S., has produced two journal volumes: Recent Advances in Texas Paleoindian Archeology: Bulletin of the Texas Archaeological Society, Vol. 78 (2007), and Recent Paleoenvironmental Research in Texas, Plains Anthropologist, Vol. 43, No. 164 (1998). He is coeditor of a new volume of essays to be published by Texas A&M University Press in October: From the Pleistocene to the Holocene: Human Organization and Cultural Transformations in Prehistoric North America.