Research confirms theory that all modern humans descended from the same small group of people

Researchers have produced new DNA evidence that almost certainly confirms the theory that all modern humans have a common ancestry.
The genetic survey, produced by a collaborative team led by scholars at Cambridge and Anglia Ruskin Universities, shows that Australia's aboriginal population sprang from the same tiny group of colonists, along with their New Guinean neighbours.

The research confirms the “Out Of Africa” hypothesis that all modern humans stem from a single group of Homo sapiens who emigrated from Africa 2,000 generations ago and spread throughout Eurasia over thousands of years. These settlers replaced other early humans (such as Neanderthals), rather than interbreeding with them.

Academics analysed the mitochondrial DNA (mtDNA) and Y chromosome DNA of Aboriginal Australians and Melanesians from New Guinea. This data was compared with the various DNA patterns associated with early humans. The research was an international effort, with researchers from Tartu in Estonia, Oxford, and Stanford in California all contributing key data and expertise.

The results showed that both the Aborigines and Melanesians share the genetic features that have been linked to the exodus of modern humans from Africa 50,000 years ago.

Until now, one of the main reasons for doubting the “Out Of Africa” theory was the existence of inconsistent evidence in Australia. The skeletal and tool remains that have been found there are strikingly different from those elsewhere on the “coastal expressway” – the route through South Asia taken by the early settlers.

Some scholars argue that these discrepancies exist either because the early colonists interbred with the local Homo erectus population, or because there was a subsequent, secondary migration from Africa. Both explanations would undermine the theory of a single, common origin for modern-day humans.

But in the latest research there was no evidence of a genetic inheritance from Homo erectus, indicating that the settlers did not mix and that these people therefore share the same direct ancestry as the other Eurasian peoples.

Geneticist Dr Peter Forster, who led the research, said: “Although it has been speculated that the populations of Australia and New Guinea came from the same ancestors, the fossil record differs so significantly it has been difficult to prove. For the first time, this evidence gives us a genetic link showing that the Australian Aboriginal and New Guinean populations are descended directly from the same specific group of people who emerged from the African migration.”

At the time of the migration, 50,000 years ago, Australia and New Guinea were joined by a land bridge and the region was also only separated from the main Eurasian land mass by narrow straits such as Wallace's Line in Indonesia. The land bridge was submerged about 8,000 years ago.

Australia's archaeological record provides several apparent inconsistencies with the “Out Of Africa” theory. In particular, the earliest known Australian skeletons, from Lake Mungo, are relatively slender and gracile in form, whereas younger skeletal finds are much more robust. This robustness, which remains, for example, in the brow ridge structure of modern Aborigines, would suggest either interbreeding between homo sapiens and homo erectus or multiple migrations into Australia, followed by interbreeding. The archaeological data also indicates an intensification of the density and complexity of different stone tools in Australia during the Holocene period (beginning around 10,000 years BP), in particular the emergence of backed-blade stone technology. The first dingos arrived at around the same time, and it is thought both were brought to the continent by new human arrivals – leading to theories of a secondary migration that has resulted in disputes regarding the single point of origin theory.