A CRATER, believed to have been created by the impact of an asteroid or comet, has been identified in the Vredefort in the Free State as largest and oldest in the world, renowned palaeo-anthropologist Professor Philip Tobias said on Wednesday. Speaking at a Standard Bank sponsored millennium lecture on human evolution at Linder Auditorium in Johannesburg, Tobias said the crater, which is between 250km and 300km in diameter, was long thought of to be of volcanic origin. The town of Vredefort is situated at the centre of crater. Professor Uwe Reimold and his group in the Geology Department at Wits, in collaboration with colleagues at the University of Potchefstroom, recently showed that the structure was caused by the impact of an extra-terrestrial object such as an asteroid or comet, Tobias said.