Neanderthals May Not Have Truly Gone Extinct — Their Genes Were Gradually Absorbed, Study Finds

Neanderthals May Not Have Truly Gone Extinct — Their Genes Were Gradually Absorbed, Study Finds

New research suggests that Neanderthals may not have vanished in the traditional sense. Instead, sustained interbreeding with expanding Homo sapiens populations could have diluted distinct Neanderthal genomes until they were nearly invisible within our species.

The team, led by computational chemist Andrea Amadei (University of Rome Tor Vergata) with evolutionary geneticist Giulia Lin and ecologist Simone Fattorini, developed a simple mathematical model to explore this scenario. Using birth and replacement rates observed in modern hunter-gatherer groups, the model estimates that persistent gene flow could reduce recognizable Neanderthal genetic signatures to near-zero in roughly 10,000–30,000 years.

Crucially, the authors ran the model under a neutral assumption — that Neanderthal genetic contributions provided no particular survival advantage to early modern humans. Even under those conditions, genetic drift combined with repeated interbreeding was sufficient to produce the pattern we see in present-day genomes. If some Neanderthal variants were advantageous, the assimilation effect would be even stronger.

"Our results provide a robust explanation for the observed Neanderthal decline that complements archaeological and genomic evidence for gradual assimilation rather than abrupt extinction," the authors write.

Genomic and archaeological data now indicate that Homo sapiens and Neanderthals mated across Eurasia for tens of thousands of years. Today, most people with non-African ancestry carry about 1–4% Neanderthal DNA. The new model does not exclude other contributing factors to Neanderthal disappearance — such as climate change, loss of genetic diversity, or competition — but it highlights how demographic pressure and gene flow alone can reshape ancestral identities.

The findings are consistent with archaeological interpretations that favor a gradual decline of Neanderthal populations in Europe. Some evidence suggests multiple waves of Homo sapiens migrations out of Africa, possibly beginning much earlier than once thought; each incoming group could have absorbed local Neanderthal communities over time.

Rather than viewing Neanderthals as wholly separate from modern humans, some researchers now argue the two represent closely related populations within a broader human lineage. Neanderthals were technologically and culturally capable — producing sophisticated tools, cave art, and controlled use of fire — and likely had complex communication abilities.

While Neanderthal cultures and distinct populations no longer survive, their genetic legacy endures inside modern humans. In that sense, they remain both our cousins and part of our ancestry. The study was published in Scientific Reports.