Spectacular skull discovery in Georgia.

 Spectacular skull discovery in Georgia.

 

The spectacular fossilized skull of an ancient human ancestor that died nearly two million years ago has forced scientists to rethink the story of early human evolution. Anthropologist, scientists who study human development, unearthed the skull at a site in Dmanisi, in southern Georgia in the west of Asia, where other remains of human ancestors, simple stone tools and long-extinct animals have been dated to 1.8 million years old. Experts believe the skull is one of the most important fossil finds to date, but it has proved as controversial as it is amazing Analysis of the skull and other remains at Dmanisi suggests that in the past scientists may have been too ready to give different names to species of human ancestors who were discovered at different places in Africa. Many of those names may now have to be wiped from the textbooks.

 

The latest fossil is the only complete skull ever found of a human ancestor that lived at the time when our predecessors first walked out of Africa. The skull adds to a collection of bones recovered from Dmanisi that belong to five individuals, most likely an elderly male, two other adult males, a young female and a juvenile of unknown sex.

 

The site was a busy watering hole that human ancestors shared with giant extinct cheetah-like animals, sabre-toothed cars and other beasts. The carcasses of the individuals were found in collapsed dens where carnivores had apparently dragged them to eat. They are thought to have died within a few hundred years of one another. ‘Nobody has ever seen such a well-preserved skull from this period,’ said Christoph Zollikofer, a professor at Zurich University’s Anthropological Institute, who worked on the remains. ‘This is the first complete skull of an adult early Homo. They simply did not exist before, ‘ he said’. Homo as a species emerged around 2.4m years ago and includes modern humans.

 

But while the skull itself is spectacular, it is the implications of the discovery that have caused scientists in the field to pause for thought. Over decades excavating sites in Africa, researchers have named half a dozen different species of early human ancestor, but most, if not all, are now on shaky ground. The most recently unearthed individual had a long face, big teeth, and a very small braincase.

 

The remains at Dmanisi are thought to be early forms of Homo erectus, the first of our relatives to have body proportions like a modern human. The species arose in Africa around 1.8m years ago and may have been the first to harness fire and cook food. The Dmanisi fossils show that Homo erectus migrated as far as Asia soon after appearing to Africa.

 

The latest skull discovered in Dmanisi probably belonged to an adult male and was the largest of the collection. I had a long face and big teeth. But just under 550 cubic centimetres, it also had the smallest braincase of all the individuals found at the site. The odd dimensions of the fossil prompted the team to look at normal skull variation, both in modern humans and chimps, to see how they compared. They found that while Dmanisi skulls looked different from one another, the variations were no greater than those seen among modern people and among chimps.

 

The scientists went on to compare the Dmanisi remains with those of supposedly different species of human ancestors that lived in Africa at the time. They concluded that the variation among them was no greater than that seen at Dmanisi. Rather than being separate species, the human ancestors found in Africa from the same period may simply be formal forms of Homo erectus.

 

‘Everything that lived at the time of the Dmanisi remains was probably just Homo erectus’, said Professor Zollikofer. ‘We are not saying that scientists did things wrong in Africa, but they didn’t have the reference points we have. Part of the community will like it, but for another part I will be shocking news.’

 

David Lordkipanidze at the Georgian National Museum, who lead the Dmanisi excavations, said ‘If you found the Dmanisi skulls at isolated sites in Africa, some people would give them different species names. But one population can have all the variation. Five or six names are being used, but they could all be from one family.’