Origin of man - new questions

2003-02-04 14:24

Jorisna Bonthuys

Cape Town - New research at the Sterkfontein Caves near Johannesburg is stirring up the debate on the origin of man and may even spark controversy in anthropological circles.

The theory that man's ancestors walked on four legs before learning to walk erect is incorrect. This has become evident from studies on "Little Foot", one of the caves' most famous residents.

This nearly complete skeleton of a 3.3 million-year-old ape man - the first Australopthecus - show that these human ancestors were able to walk upright when they left the trees, doctor Ron Clarke says. He says they were less chimpanzee-like than was believed up till now.

Clarke, a renowned palaeontologist from the University of the Witwatersrand, recently published his research on Little Foot in the South African Journal of Science.

This comes after fragments of Little Foot's hip, thigh, hand and foot bones, as well as parts of the cranium, were discovered. Clarke, who has studied the skeleton since 1997, says the new evidence allowed him to determine how the ape-man walked and how he used his limbs.

The find has opened up a new debate on the relationship between man and the chimpanzee. Researchers have been grappling with the composition of man's genetic origins for decades.

Clarke's research has created a new way of comparing the relative length of the skeleton's arms in relations to his legs. As opposed to humans and apes, the lengths of Little Foot's limbs are virtually the same. The arms of apes are longer than their legs, while modern man has longer legs than arms.

The other "clue" is that Little Foot's left hand shows many similarities to that of modern man. It has relatively short fingers and a long thumb, compared to the specialised long fingers and short thumbs that allow apes to swing on trees.

Gorillas and chimps fold their thumbs into their palms when they walk on their knuckles and use all four limbs to carry out this action.

"This shows that this human ancestor did not walk on his knuckles like African apes, but walked erect when it left the trees," Clarke says. His says this hominoid probably spent a lot of time in trees.

Clarke doubts whether humans and chimpanzees did have a common ancestor five to eight million years ago. If there were indeed a common ancestor, it must have been about 15 million years ago, before the chimpanzee and gorilla developed specialised hands.

Sterkfontein is often referred to as the "cradle of humankind". About 500 hominoid fossils have been found in the area. Visit www.nrf.co.za for more information.

- Die Burger