April 24, 2003. Copyright 2003. Graphic News. All rights reserved.

Cradle of Mankind dated 4 million years ago

LONDON, April 24, Graphic News: The story of the origin of man looks likely to be rewritten yet again with the discovery that new Australopithecus fossils found in caves in South Africa -- along with a nearly complete skeleton discovered there in 1997 -- may have been buried about four million years ago, as much as one million years earlier than previously thought. 

These remains and similar specimens from East Africa are now some of the earliest examples of these hominids (ape-men), according to Timothy Partridge and others at the University of Witwatersrand in South Africa and Purdue University in West Lafayette, Indiana, United States. 

Writing in the April 25 issue of the journal Science, the authors estimated how long the fossils had been buried by measuring the decay of radioactive isotopes in cave sediments. ÒWe used burial dating by the radioactive decay of the Ôcosmogenic nuclidesÕ aluminium-26 and beryllium-10 in quartz in the cave sediment,Ó said Professor Partridge.

The isotopes formed when quartz grains were bombarded by cosmic rays at the EarthÕs surface millions of years ago. When the rocks were later buried, production of the isotopes stopped. By measuring their slow decay the Partridge team calculated how much time had passed since the rocks were buried in the caves of Sterkfontein.

Situated 30 miles (50 kilometres) west of Johannesburg, Sterkfontein is the richest fossil hominid site in the world. Known as the ÒCradle of Mankind,Ó the limestone caves have yielded many discoveries of our human evolutionary past, including the legendary ÒLittle FootÓ hominid found in 1997 by Dr Ron Clark, a member of the Witwatersrand team, and ÒMrs Ples,Ó found in 1947 by Dr Robert Broom.

Both Little Foot and Mrs Ples were part of the genus Australopithecus.ÊThe anatomy of the ankle joints shows that the four feet-tall (1.22 metres-tall) hominids were bipedal (able to walk upright) while maintaining the ability to climb trees effectively by the feature of an opposable big toe.ÊAnother discovery at Sterkfontein was the skull of a so-called Taung child in 1924, the first fossil to be found that belonged to the genus Australopithecus. 

Some palaeoanthropologists say that we are direct descendants of Australopithecus. Other argue these early ancestors were our cousins -- off-shoots of the family who then died out -- or one of the many missing links between humans and apes.

Previously, the most complete early hominid was ÒLucy,Ó an Australopithecus dated between 3.6 million and 2.9 million years old, whose partial skeleton was discovered in 1974 in Ethiopia. The oldest complete skeleton before this latest discovery dates back to 1.8 million years, said Clarke. It was that of a Homo Erectus, found in Kenya.
/ENDS

Source: Science