Scientists have sequenced the genome of the earliest-dated modern human, giving them an unprecedented look at the early genetics of our species as we know it. By getting closer than ever to the point at which Neanderthals and humans interbred, the new genome also gives scientists a much more accurate date range for that fateful interaction: between 50,000 and 60,000 years ago.
The male, whose genome is reported in this week’s Nature, lived 45,000 years ago in what is now Siberia and was found near the settlement of Ust’-Ishim. This makes him the earliest-dated modern human found outside Africa or the Middle East; the previous earliest to have his genome sequenced was more than 20,000 years younger.
According to corresponding author Janet Kelso, a researcher at the Max Planck Institute for Evolutionary Anthropology, the man’s femur provided an amount of genetic information comparable to what we know about humans today.
“We now have some idea how people who lived 45,000 years before present were related to present-day people,” Kelso said
They found, for example, that the man was equally closely related to modern-day Asians and early Europeans. They believe this means that the man came from a group of people that diverged from Europeans and Asians around the same time (or even before) those groups diverged from each other.
Kelso and her colleagues were able to compare the amount of Neanderthal DNA in each to better pinpoint when our ancestors intermixed with the other group. Until now, estimates have been vague, with researchers setting the date at 37,000 to 86,000 years ago.
The amount of Neanderthal ancestry found in Ust’-Ishim man was very similar to what we see in people today, indicating that the interbreeding had already occurred and ended when Ust’-Ishim came along. But because the Ust’-Ishim man was born much closer to the time of the genetic mingling, Kelso and her colleagues were able to analyze his DNA for a more accurate time stamp – 7,000 to 13,000 before he lived, or about 50,000 to 60,000 years ago.
But the man’s location may be his most surprising feature. According to Kelso, previous expeditions had found tools in Siberia that were dated to this man’s age and seemed to be the work of humans – but this would be the first direct evidence that modern humans lived there at the time.
Scientists have a lot to learn about the earliest humans – and the Neanderthals they co-existed with. Kelso hopes to see older and older genomes sequenced. “[But] this will require substantial technical developments, both in the lab and computationally,” she said.