Ever wondered why your partner is up with the lark (百灵鸟) while you are happily sleeping till noon? It could be thanks to Neanderthal genes, according to a new study.
Scientists comparing ancient DNA with the genetics of modern humans discovered a "striking trend", said John Capra, an epidemiologist (流行病学家) at the University of California in San Francisco. The researchers found that the Neanderthal genes that remain affect the body clock —increasing tendency to be a morning person.
Neanderthals lived at higher latitudes (纬度) than our ancestors who migrated from Africa — further away from the equator, with the days longer in summer and shorter in winter. "The gene that makes people early risers likely enables more rapid alignment (协调一致) of the circadian clock (生物钟) with changing seasonal light patterns," Dr Capra said, "when Neanderthals were able to make the most of daylight hours to hunt."
Scientists have previously explored how the circadian rhythms of insects, plants, and fish have developed depending on latitude. But that hasn't been well studied in humans. There searchers wanted to see whether there was a genetic reason for differences in circadian rhythms between Neanderthals and modern people, and found 16 variants (变异体) associated with greater "morningness". They suspected that as Neanderthals and the ancestors of modern humans mated, people today could have followed Neanderthal "circadian variants".
To test this, scientists analyse the genetics of several hundred thousand people from the UK Biobank and found many of the variants that affect sleep preference. "Most noticeably, they found that these variants increase morningness," the researchers said. This is consistent with what has been found in other animals that have adapted to living at a high latitude, as Neanderthals did.
