When the ancestors of modern Eurasians migrated out of Africa and interbred with Eurasian archaic hominins, namely Neanderthals and Denisovans, DNA of archaic ancestry integrated into the genomes of anatomically modern Homo sapiens. This process potentially accelerated adaptation to Eurasian environmental factors, including reduced ultra-violet radiation and increased variation in seasonal dynamics. In new research, scientists from Vanderbilt University, the University of Pennsylvania and the University of California, San Francisco discovered lineage-specific genetic differences in circadian genes and their regulatory elements between humans and Neanderthals. They found that introgressed gene variants are enriched for effects on circadian regulation, consistently increase propensity for morningness in Europeans. The results expand our understanding of how the genomes of humans and our closest relatives responded to environments with different light/dark cycles.
All anatomically modern humans trace their origin to the African continent around 300,000 years ago, where environmental factors shaped many of their biological features.
Although they arrived in Eurasia 70,000 years ago, other hominins — Neanderthals and Denisovans — lived there for more than 400,000 years.
These archaic hominins diverged from anatomically modern humans around 700,000 years ago, and, as a result, the ancestors of humans and archaic hominins evolved under different environmental conditions.
“While there was substantial variation in the latitudinal ranges of each group, the Eurasian hominins largely lived at consistently higher latitudes and, thus, were exposed to higher amplitude seasonal variation in photoperiods,” said University of California, San Francisco’s Dr. John Capra and his colleagues.
“Given the influence of environmental cues on circadian biology, we hypothesized that these separate evolutionary histories produced differences in circadian traits adapted to the…
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