Neanderthals and modern humans may have interbred 50,000 years earlier than previously thought, a new study found.

Early modern humans were said to have originated from Africa, while Neanderthals lived outside that continent. The two species found each other and eventually interbred after the so-called "out of Africa" migration less than 65,000 years ago. In the new study, however, a team of international researchers were able to find the first proof that early modern humans migrated out of Africa even before this time.

The study findings may pave the way for more information about the patterns of migration that transpired many years ago.

Interbreeding Long Before The Great African Exodus

Present-day Europeans, Asians and Eurasians have Neanderthal traces in their genomes. Even if they were raised out of Africa and were raised with other humans, their DNA cannot hide the fact that they have Neanderthal origins.

Modern Africans, however, do not have fragments of Neanderthal DNA in their genomes. This means that sexual contact with Neanderthals only transpired among those modern-day humans who left Africa.

Study co-author Ilan Gronau says Africans today may not have the chance to interbred with Neanderthals.

Opposite Gene Flow

"One very interesting thing about our finding is that it shows a signal of breeding in the 'opposite' direction from that already known," says co-team leader Adam Siepel. He pertains to their discovery of human DNA in Neanderthal genome, instead of Neanderthal DNA in the human genome.

The researchers were able to make this discovery after studying the remains of a particular Neanderthal woman found in the Altai Mountains. They assume that this so-called "Altai Neanderthal" was one of those who left Africa earlier than the rest of her group.

The team also analyzed two Neanderthal remains found in caves located in Croatia and Spain. Both samples do not have modern human DNA.

The scientists also analyzed the DNA of another extinct human called Denisovans, who are considered, along with the Neanderthals, as human cousins. Both lived in the same cave, but at different periods of time.

The findings of the Denisovan DNA analysis show that the species do not have DNA of modern humans, but the Neanderthals do. However, this does not signify that modern humans never had sex with Denisovans nor European Neanderthals.

The study was published in the journal Nature on Wednesday.

Photo: Erich Ferdinand | Flickr