The present day humans and Neanderthals are believed to have interbred much earlier than though during the prehistoric era, the period of interbreeding dating as far back as around 100,000 years ago, scientists have claimed in a new study published Wednesday in the journal Nature.

Earlier, scientists had estimated that the interbreeding started around 50,000 to 60,000 years ago. But an international research team has established “strong evidence” that Neanderthals and modern humans started mating much earlier than that.

It was in 2010 that the researchers for the first time sequenced the first Neanderthal genome, thus defining how much related we are to our ancient, extinct cousins. All non-African modern humans have acquired 1-4% of their DNA from Neanderthals.

However, no evidence of this mating interaction has yet been found in the DNA of the Neanderthals.

Adam Siepel, a computer scientist using simulations to study genetics, explains, “Instead of leaving fragments of Neanderthal DNA in modern humans, we find fragments of modern human DNA in the Neanderthal genome. And that mating event happened some 100,000 years ago”.

The team of geneticists, anthropologists and other computer scientists — Dr. Siepel too was its member — claims to have found that a Neanderthal specimen from Siberia shared at least 1% of its DNA with modern humans.

Neanderthals are also our closest evolutionary relative, and scientists know that at some point tens of thousands of years ago, Neanderthals and Homo sapiens mated to some degree.

Scientists have based their findings on the genome of a Neanderthal woman whose remains were found in a cave in the Altai Mountains in southern Siberia near the Russia-Mongolia border. In the remains, the researchers were able to detect residual DNA from Homo sapiens, a sign of inter-species mating.