Mail and Guardian

Book ID 583

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Mail and Guardian,
Extract Date: December 20 1999

Clarke uses chimps to prove theory

Dr Ronald Clarke used circus chimpanzees to prove his theory about the Laetoli footprints in Tanzania.




TWENTY years ago, Dr Ronald Clarke was invited by famed palaeoanthropologist Mary Leakey to continue an excavation begun at Laetoli in Tanzania.

An American chemistry professor from Rhode Island, Paul Abell, had discovered a hominid heel impression in 3,6-million-year-old volcanic tuff, or sediment formed out of volcanic ash. Subsequent excavation by Tim White of the University of California at Berkeley uncovered the first footprints of a trail made, apparently, by two individuals.

Clarke accepted Leakey's invitation -- and inadvertently entered an arena of fierce debate.

The prints were clearly made by individuals walking bipedally (upright on two legs) but Leakey and Clarke differed in their interpretations. Says Clarke, "I was struck by the fact that the prints did not seem fully human: there was separation of the big toe from the other toes, and, behind the end of the big toe, a smallish round impression that looked like a toe.

"Mary -- advised by other experts -- insisted it was Homo, and that the second of the two trails must have been made by one individual walking in another's footprints. I, on the other hand, thought the prints were [made by one creature:] ape-like with long toes -- not fully human."

Public outcry greeted Clarke when he stated his views in 1985 at the conference celebrating the 60th anniversary of the Taung discovery, and he didn't publish them. But he was not convinced he was wrong. Later that year he arranged an experiment with the Boswell Wilkie Circus in Johannesburg -- and a friendly trainer -- to coax a female and a male chimpanzee to walk next to each other bipedally over wet sand.

"The circus chimps produced prints that looked like the Laetoli footprints," Clarke recalls. "Not only did those of the male look similar -- big toe aligned with the others plus the 'apparent' toe within, caused by the imprint of a joint -- but also the female had a completely different footprint. She was more timid -- she dug her heels in and spread her big toe wide and kicked up a lot of sand -- whereas he was confident and tended to walk with his big toe most often close to the other toes.

"The circus prints showed that apes with toes capable of opening up to a wide degree can also bring that toe into alignment when they walk upright -- they are capable of doing both."

The conclusion -- in a scientific paper published this month -- is that "when the chimpanzee walked bipedally in a confident manner, it preferred to align its big toe with the others, presumably for more efficient locomotion".

The foot bones of the 3,33-million-year-old skeleton at Sterkfontein have inadvertently given Clarke a further -- perhaps clinching -- argument. Comparing the evidence of the foot bones, the footprints in Tanzania, and those made by the circus chimps, Clarke has announced: "The Laetoli footprints could [in fact] have been made by feet with slightly divergent big toes as represented by the Sterkfontein Australopithecus StW 573."

-- The Mail & Guardian, December 20 1999.

Extract ID: 3294