A new theory says Neanderthals weren't a separate group that split off early—they were actually formed by modern humans moving around 300,000 years ago.
bioRxiv · March 13, 2026 · 10.64898/2026.03.11.711219
Why it matters
This hypothesis overturns the standard view that Neandertals and modern humans were isolated for hundreds of thousands of years. It provides a simple explanation for why Neandertals carry modern human Y chromosomes and mitochondrial DNA, which has long perplexed geneticists.
From the abstract
This paper demonstrates the feasibility of the hypothesis that Neandertals formed when a population using recently developed Levallois stone tool technology expanded between 400-250 thousand years ago (ka). In Europe, their range expansion into an area with Sima de los Huesos-like people led to massive introgression of local archaic genes producing a population with around 95% archaic ancestry (Neandertals); if this range expansion was sex-biased it would provide a simple explanation for why Nea