Human Ancestor?

Australopethicus sediba handFrom CSIRO Science by Email. Fossils discovered in a South African cave have provided another piece of the puzzle of human evolution. The bones belong to a hominin called Australopithecus sediba. Hominins refers to the group that includes modern and extinct human species and their ancestors.

Australopithecus became extinct about two million years ago and its exact relationship to modern humans is unclear. Many scientists think that humans are not directly descended from Australopithecus – they are more like our distant cousins. Australopithecus walked upright like us and it is possible they used simple stone tools.

Palaeoanthropologists (scientists who study ancient human fossils) were particularly interested in the fossil’s hand. Well preserved hominin hand fossils are rare, but these fossils were in particularly good condition. Au. sediba had a relatively long thumb and short fingers, indicating it might have been able to grip and manipulate objects like a human. What is interesting is that it also had long arms, like those of other apes. The foot was similar; it had an ape-like heel, but an ankle like a human’s.

The fossils were accurately dated by the University of Melbourne and found to be 1.98 million years old. This date is significant as it is after other species of Australopithecus were believed to have become extinct, but before it is reliably known that human species emerged.

Professor Lee Berger, who discovered the fossils in 2008, believes Au. sediba could challenge current theories about human evolution. Lee thinks that the combination of human and ape-like traits in Au. sediba suggest that it is a link between Australopithecus and humans. Australopithecus may be more than just a long-lost cousin – it may be our direct ancestor.

Human evolution is a controversial topic and not everyone agrees with Lee’s idea. Linking a physical feature such as the structure of the hand to behaviour, such as using tools, is difficult to prove.

Further research on such hominin fossils will hopefully produce more clues. One day, we may be able to fill even more gaps in our evolutionary family tree.

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