Asian descendent?: Martinón-Torres examines an early European human skull found in Dmanisi, Georgia.

Credit: National Centre for the Investigation of Human Evolution

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SYDNEY: The first human species to make it to Europe one and a half million years ago may have come from Asia, not Africa, according to an analysis of 5,000 fossil teeth.

“It had been assumed for a long time that that the colonisation of Eurasia was the result of several out-of-Africa migrations,” said Maria Martinón-Torres, from the National Centre for the Investigation of Human Evolution in Burgos, Spain.

But Martinón-Torres and her team now present evidence that migration from Asia may have had a greater impact. Their results are published this week in the U.S. journal the Proceedings of the National Academy of Sciences.

Out-of-Asia?

It is generally accepted that Homo habilis, the earliest species from the genus Homo, appeared in Africa around two million years ago. Its first Eurasian descendants have been dated to several hundred thousand years after this. Over the next 1.5 million years, other migrations out of Africa are believed to have taken place.

The most recent of these – around 150,000 yeas ago – is believed by many anthropologists to have been made by anatomically modern humans that are the ancestors of all people alive today.

However, there is considerable debate about the extent to which these later African migrations impacted upon the evolution of the preexisting early human populations in Europe and Asia – such as Homo heidelbergensis, which lived from 800,000 to 300,000 years ago.

In order to try and understand more about the relationships between early African, European and Asian populations, Martinón-Torres and her team studied the shape of 5,000 teeth from a range of early humans from the Australopithecus and Homo groups of species, spanning a two-million-year period. In the absence of ancient DNA, fossilised teeth are a useful proxy, said the researchers, as their shape has a large genetic component.

The researchers found that Eurasian fossils, such as H.neanderthalensis and Homo erectus, had more in common with each other than with their African counterparts, including Homo habilis and Australopithecus afarensis.

The absence of a strong African influence over the Eurasian teeth leads the authors to speculate that Asian populations may have played a larger role than African in colonizing Europe, beginning one and a half million years ago. Based on the studies of dentition, Martinón-Torres argued that from this time until around 250,000 years ago, the evolutionary courses of the Eurasian and the African continents were relatively independent.

Savanna spread

Contrary to the prevailing theory, Asia may have served as a centre for the production of human species, she said.

“The first hominin clearly attributed to the genus Homo, was in fact found outside of Africa, and we cannot discard the possibility that it is an ancestor of some African species,” said Martinón-Torres. “Migrations can be not only from Africa to Eurasia, but also from Eurasia to Africa and from one side of Eurasia to the other.”

According to David Bulbeck from the Australian National University’s School of Archaeology and Anthropology, in Canberra, the research "suggests that a very early Homo species, which was present in both Africa and Eurasia, subsequently split into African and Eurasian lineages.”

Bulbeck pointed out that such a scenario would be consistent with other research which suggests that during this time an expanse of “savannaland” – preferred habitat for early humans – was found from Africa all the way through southern Europe and into Asia.