First, it’s worth learning a bit of background. Neanderthals are an extinct species of human who died out around 30,000 years ago, but not before leaving a bit of themselves behind in almost all non-Africans living today.
Scientists believe that modern humans migrating out of Africa crossed paths with Neanderthals perhaps living alongside them for as long as 5,000 years. Not a long time in an evolutionary timescale, but long enough to intermix. The result: all non-Africans living today carry some of our ancient relatives DNA.
The absence of Neanderthal DNA in people of African descent points to the history of human migration, and indicates that the intermixing of Neanderthals and our modern humans must have occurred soon after the movement out of Africa, but likely before the large migrations into Europe and Asia out of the Middle East. People often want to know what the average percentage of Neanderthal ancestry individuals typically have.
This number will vary, but is usually somewhere between 1 and 4 percent. So for example if you have 3.1 percent, that would place you in the 97th percentile, meaning you’d have more Neanderthal in youn than 97 of 100 23andMe users! How do we derive the specific percentage of ancient ancestry your DNA contains? It’s pretty complicated, but basically we compare two modern human genomes with the Neanderthal genome and then plot individual data on a trained axis.
Check out Eric Durand’s white paper, which gives a much more technical explanation of this calculation.
Recent studies have also shown that there may have been intermixing with other ancient species as well. Another ancient relative, the Denisovans (named for Denisova cave in Siberia), share even more DNA ( between 4-6 percent on average ) with present-day Melanesians (people of Vanuatu, the Solomon Islands, Fiji, and Papua New Guinea). However,
we don’t currently have a feature for Denisovan ancestry.
Based on this discovery, there may be other ancient human species who we share DNA with, who could have contributed to our lasting modern-day genomes. Why should you care? While the Neanderthal DNA may not tell us much about what features and traits we share with this ancient species, the DNA we do not share could hold the key to why Neanderthals went extinct and why we, modern humans, became the evolutionary winners.