Neanderthals carried up to 3.7 percent modern human DNA from two separate waves of interbreeding
A team analyzed whole genome sequences from 2,000 modern humans and three Neanderthals to measure gene flow between the groups. They found Neanderthals possessed between 2.5 and 3.7 percent modern human ancestry. The data revealed two distinct waves of modern human gene flow into Neanderthal populations. Using the human-introgressed sequences, researchers revised earlier estimates of Neanderthal ancestry in modern humans. The work also showed Neanderthal population sizes were significantly smaller than previous studies had calculated.
The findings clarify the extent and timing of ancient interbreeding and reveal that gene flow between the groups was recurrent rather than a single event.
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