The problem with thinking you’re part Neanderthal

A groundbreaking 2024 study by French population geneticists Lounès Chikhi and Rémi Tournebize challenges one of evolutionary biology's most celebrated discoveries: that modern humans carry Neanderthal DNA from ancient interbreeding. The researchers argue that the statistical models supporting this 'inner Neanderthal' theory rely on flawed assumptions about random mating in huge, continent-sized populations. Instead, they propose that population structure—where ancient Homo sapiens evolved in smaller, geographically isolated groups—could produce the same genomic patterns without any interspecies sex at all.

This challenge targets the foundation of Svante Pääbo's Nobel Prize-winning work from 2010, when his team first sequenced the Neanderthal genome and found that non-African populations share 1-4% of their DNA with Neanderthals. Chikhi and Tournebize's alternative explanation suggests that genetic similarities might result from ancient population subdivisions within Africa, not from romantic encounters between species in Europe 45,000 years ago. Their work highlights a broader methodological crisis in evolutionary genetics, where sophisticated algorithms often rest on oversimplified assumptions about how populations actually interacted.

The implications extend far beyond Neanderthal ancestry. If population structure has been systematically underestimated, it could reshape our understanding of human migration patterns, disease genetics, and even how we interpret the genomic differences between modern populations. As University of Cambridge geneticist William Amos notes, many evolutionary models are 'based on simple assumptions that are often wrong'—a problem that affects everything from tracing human origins to studying genetic predispositions to disease.