Neanderthal-Sapiens: did the DNA crossing occurred 50-60 thousand years ago?
The discovery of a man's femur found in 2008 in Siberia suggests that in Europeans and Asians there is less Neanderthal genetic heritage than previously thought. The "mixing" probably occurred in the Middle East.
Recent discoveries unveiled that contemporary humans possess a smaller proportion of Neanderthal genetics than previously believed, pinpointing the epoch of interbreeding between our forebears and these extinct relatives to a timeframe between 50,000 and 60,000 years ago.
We know this thanks to analysis of the oldest DNA sequence from modern humans, extracted from the genome of a Homo sapiens who inhabited Siberia around 45,000 years ago.
In 2008 Nikolai Peristov, a hobbyist in the quest for prehistoric remains, while on the lookout for mammoth tusks stumbled upon a human femur along the Irtysh River's banks near Ust-Ishim in Western Siberia. Subsequent carbon-14 dating techniques confirmed the bone to be from a male Homo sapiens who lived 45,000 years ago. While not the oldest human DNA to be sequenced - the oldest one belongs to a hominide dating back 400,000 years - it is the earliest confirmed to belong to a Sapiens located outside Africa and the Middle East.
The DNA of this ancient Siberian featured Neanderthal DNA segments significantly longer than those observed in today's humans.
Today, Neanderthal genetic material accounts for approximately 1.6-1.8% in Europeans and 1.7-2.1% in East Asians, with none detected in African populations. However, the Ust-Ishim individual's genome contained about 2.3% Neanderthal DNA. This fin suggests that the genetic exchange between Homo sapiens and Neanderthals was minimal and that the influence of Neanderthals has not diminished over time as previously hypothesized.
From this data it is believed that the Sapiens-Neanderthal genetic crossover occurred between 232 and 430 generations prior to the life of the Ust-Ishim individual, narrowing the previously assumed timeframe of interbreeding from between 37,000 and 86,000 years ago to between 50,000 and 60,000 years ago. This period aligns with when Sapiens, having migrated out of Africa - where our species evolved around 200,000 years ago - were approximately situated in the Middle East.
The Ust-Ishim man belonged to a cohort of Sapiens yet to diverge into distinct groups headed towards Europe and Central and East Asia. The discovery raises questions about other Sapiens fossil findings in India and the Middle East dating back 100,000 years.
It is possible that multiple "waves" of Sapiens migrated from Africa, with the earliest eastward migrants disappearing without a genetic trace. Probably all contemporary humans are descended from the last groups to leave Africa about 60,000 years ago, painting a complex picture of human evolution and migration.
