A new study has shown that humans interbred with Neanderthals approximately 100,000 years ago, between 40,000 and 50,000 years earlier than first thought.

The new study, published in the journal Nature, reports that genetic analysis of the remains of a Neanderthal woman detected residual DNA from Homo sapiens, a sign of inter-species mating.

The discovery by the Max Planck Institute for Evolutionary Anthropology forces scientists to reasses the accepted timeline of when humans migrated out of Africa to other parts of the world.

One theory is that the recently discovered interbreeding arose from what scientists call a failed dispersal. That refers to a small population of Homo sapiens trekking to the Middle East and other parts of Eurasia, but failing to establish lasting colonies.

The remains of the Neanderthal woman at the center of the study were found in southern Siberia, near the border with present-day Mongolia.

We don't know what happened to them," geneticist Martin Kuhlwilm told Reuters. "It seems likely that this population went extinct, either by environmental changes or maybe direct competition with Neanderthals ... It implies that modern humans left Africa in several waves, some of which probably went extinct."

Neanderthals, renowned for their skill as hunters, lived in modern-day Europe and Asia. The last of them are believed to have died out approximately 40,000 years ago.

Last week, a study published in the journal Science presented evidence that one bit of Neanderthal DNA can boost the risk of tobacco addiction, while others can slightly raise or lower the risk of being diagnosed with depression. Past studies have suggested Neanderthal DNA raises the risk of allergies.

Neanderthals and modern people split off from each other on the evolutionary tree an estimated 600,000 years ago. In people of Asian or European ancestry, around 2 percent of DNA can be traced to Neanderthals.

The Associated Press contributed to this report.

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