A new study published in Nature on October 23rd suggests that Homo Sapiens — modern man — was more widespread across Europe some 50,000 years ago than previously believed. The research involved studying a 45,000-year-old leg bone from Siberia, and has produced the oldest genome sequence for Homo sapiens on record, as well as providing evidence a hitherto-unknown population of humans that lived in northern Asia. The researchers managed to get a full DNA sequence from the leg bone of a male hunter-gatherer, which showed that human interbreeding with Neanderthals had occurred some five to ten thousands years before his birth.

DNA Pinpoints Homo Sapiens-Neanderthal Interbreeding

More on Ust’-Ishim femur

Nikolai Peristov, a Russian artist who makes jewellery from mammoth tusks found the femur bone back in 2008. He was searching for ivory along Siberia’s Irtysh River when he saw a bone sticking up out of the riverbank mud. He dug up the bone and took it to a police forensic scientist.

Amazingly, the bone turned out to be a human left femur, and it was sent to the Max Planck Institute for Evolutionary Anthropology in German where it was carbon-dated. Moreover, the bone contained preserved DNA, which could be sequenced to determine the genome to the same accuracy as with modern human genomes.

The scientists decided to name the fossil Ust’-Ishim, after the district where the remains were discovered. It turned out Ust’-Ishim was between 43,000 and 47,000 years old, almost twice as old as the next-oldest known complete modern-human genome.

More precise date for Homo Sapiens-neanderthal interbreeding

Of note, around 2% of Ust-Ishim’s genome comes from Neanderthals, about the same percentage that is found in modern non-African humans, due to widespread interbreeding between Neanderthals and Homo Sapiens. Past studies suggest the interbreeding occurred after the common ancestors of Europeans and Asians left Africa and came across Neanderthals in the Middle East.

The timing of the interbreeding was relatively vague until now, but was generally believed to be between 37,000 and 86,000 years ago. The Neanderthal DNA in Ust’-Ishim’s genome, however, makes it possible to pinpoint the timing to between 50,000 and 60,000 years ago given the long Neanderthal DNA segments in the Ust’-Ishim man’s genome. The paternal and maternal chromosomes are mixed up in every generation, so that over time the DNA segments from any individual naturally become shorter.