Definition
Neanderthal introgression is the introduction of Neanderthal genetic material into modern human populations through interbreeding events that occurred when dispersing modern humans encountered Eurasian Neanderthals roughly 50,000 to 60,000 years ago. The result is a persistent legacy: every non-African human alive today carries approximately 1 to 4 percent Neanderthal-derived DNA scattered across the genome.
The discovery, published in 2010 from the first full Neanderthal genome by Pääbo's lab, overturned the strict replacement model. The Out-of-Africa dispersal did not simply replace archaic populations on contact; it absorbed some of their genetic variation along the way.
Why it matters
How it works
Modern humans leaving Africa around 70,000 to 60,000 years ago entered a Eurasia where Neanderthals had lived for hundreds of thousands of years. In the Levant or nearby, the two populations encountered each other, interbred at low but significant rates, and the resulting modern-human descendants carried Neanderthal DNA into all subsequent non-African populations.
Identifying Neanderthal segments in modern genomes uses statistical methods that compare modern human sequences to high-coverage Neanderthal genomes. Segments matching the Neanderthal pattern more than expected, after correcting for shared ancestry, are flagged as introgressed. The collective map across the modern human genome covers ~40 percent of the Neanderthal genome — different bits surviving in different modern populations.