A New Find in South Africa: Key Link in Human Evolution?

Evolution skeptics like to trot out the argument that if Darwin had been right, scientists would have discovered transitional fossils by now — creatures with a mix of features from earlier and later species. Since they haven't, the deniers say, evolution must not be true.

The truth is that paleontologists have found transitional species by the score, from many different time periods. But none have materialized from as crucial a point in our evolutionary past as a pair of skeletons whose discovery was announced today by the journal Science. (See the top 10 scientific discoveries of 2009.)

The fossils, which have been determined to be a new species, Australopithecus sediba, were initially found by Matthew Berger, the 9-year-old son of paleontologist Lee Berger of South Africa's University of the Witwatersrand (the elder Berger tried in vain to get the editors of Science to list Matthew as a co-author on the paper). The bones belong to a pre-teenage boy and a woman estimated to be in her late 20s or early 30s; the individuals died at about the same time, and before their remains had fully decomposed, they were entombed in an avalanche of sediment and nearly perfectly preserved deep in the Malapa cave north of Johannesburg, South Africa.

The Au. Sediba bones are important for their vintage — they date back to the moment about 2 million years ago, when the genus of human ancestors known as Australopithecus was just giving way to a new group called Homo, which would ultimately produce Homo sapiens, or modern humans.

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