Ancient skull could change the story of human evolution

18 October 2013

1.8-million-year-old skull shows diversity among single species of early humans - skulls previously identified as different species may be variations of the same species.

A total of five early human skulls have been described in Dmanisi, Georgia, with the latest proving there is a wide variation of head shapes.

The research was published today in Science, along with a comment by Museum anthropologist Prof Chris Stringer, who wrote that the team that made the discovery had made an ‘excellent case.’

Stringer showed his support for the argument that ‘this remarkable new skull, with its huge jawbone, is part of the natural variation of the Dmanisi population 1.8 million years ago, and these can all be attributed to a primitive form of Homo erectus.’

Single species?

Homo erectus is an early human species originating in Africa that came before modern humans, Homo sapiens.

Human fossil remains from the same time period as the Dmanisi site have been found in other locations, but not all are considered to be the same species as Homo erectus. Differences in shape, for example of jaw bones and brain cavities, mean these fossils are classified as different species.

This new finding challenges that idea. The fifth skull described today is the largest of the group, and has a huge jaw and a relatively small space for the brain compared to its companions.

The research team suggests that this diversity among a single group of Homo erectus means many other fossils may be misidentified as separate species. Early humans identified as Homo habilis or Homo rudolfensis may actually just be variations of Homo erectus.

New ideas

A popular idea of human evolution is that a range of human species evolved out of Africa around 2 million years ago. This new research proposes instead there may only be a single line of evolving Homo erectus humans spreading across the world.

Stringer concludes the team are probably right that some fossils will have to be reclassified, but that ‘Africa is a huge continent with a deep record of the earliest stages of human evolution,’ and that he ‘still doubts that all of the “early Homo” fossils can reasonably be lumped into an evolving Homo erectus lineage.’

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