GENETICS

When Our Ancestors Met Neanderthals

~50,500 to 43,500 years ago

Palaeolithic · Upper Palaeolithic · Last glacial

Everyone whose roots lie outside Africa carries two to three percent Neanderthal DNA, and ancient genomes have now dated the encounter: most of the mixing falls in a single extended period, between about 50,500 and 43,500 years ago, probably in southwest Asia, shared by the ancestors of all non-Africans. Natural selection then went to work quickly, purging some Neanderthal variants and favouring others.

Why it matters

The meeting is written in us rather than in stone. Its one shared date works as a clock for the whole expansion: modern human remains from outside Africa older than 50,000 years probably belong to other populations, not to the one from which every non-African genome sequenced so far descends. Immunity, skin, metabolism still bear the borrowed variants, working parts of present-day bodies inherited from a humanity that no longer exists.

Dating & uncertainty

Ancient genomes narrow the bulk of the gene flow to a single extended period between about 50,500 and 43,500 years ago, shared by all non-Africans; the earliest European genomes carry Neanderthal segments from that same pulse, dated in those genomes to roughly 49,000 to 45,000 years ago. Whether the contact lasted centuries or millennia inside that window is still open: duration is what these methods recover least well.

Sources

1. Iasi et al. (2024), Science · Neandertal ancestry through time: insights from genomes of ancient and present-day humansdoi:10.1126/science.adq3010
2. Sümer et al. (2024), Nature · Earliest modern human genomes constrain timing of Neanderthal admixturedoi:10.1038/s41586-024-08420-x
3. Iasi, Ringbauer & Peter (2021), Molecular Biology and Evolution · An extended admixture pulse model reveals the limitations to human-Neandertal introgression datingdoi:10.1093/molbev/msab210

Our species’ history as one day

20:25:083 h 35 min before midnight

if the 315,000 years of Homo sapiens were compressed into a single day