Neanderthal Introgression Shaped Human Circadian Traits.

Interbreeding between modern humans and Neanderthals created the potential for adaptive introgression as humans moved into new environments that had been populated by Neanderthals for hundreds of thousands of years. Here we discover substantial lineage-specific genetic differences in circadian genes and their regulatory elements between humans and Neanderthals. We then show that introgressed archaic alleles are enriched for effects on circadian gene regulation and consistently increase propensity for morningness in modern Europeans. These results substantially expand our understanding of how the genomes of humans and our closest relatives responded to living in environments with different light/dark cycles, and they demonstrate a coordinated contribution of archaic admixture to modern human chronotype in a direction that is consistent with adaptation to higher latitudes.