Ever wondered why your partner is up with the lark while you’re happy snoozing till noon?
It could be thanks to Neanderthal genes, according to a new study.
While the origin of modern humans can be traced back to Africa 300,000 years ago, when these ancestors moved north they interbred with Neanderthals – and traces of their DNA can be found in people today.
Scientists comparing ancient DNA with the genetics of modern humans discovered a “striking trend”, said the paper’s lead author John Capra, an epidemiologist at the University of California in San Francisco.
They found that of the Neanderthal genes that remain, many affect the body clock, “increasing propensity to be a morning person”.
Neanderthals lived at higher latitudes 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 of the circadian clock with changing seasonal light patterns”, Dr Capra said – so 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 evolved depending on latitude. But that hasn’t been well studied in humans.
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The researchers wanted to see whether there was a genetic reason for differences in circadian rhythms between Neanderthals and modern humans, and found 16 variants associated with greater “morningness” – the propensity to wake up early.
They suspected that as Neanderthals and the ancestors of modern humans mated, people today could have inherited Neanderthal “circadian variants”.
To test this, scientists analysed the genetics of several hundred thousand people from the UK Biobank and found many of the variants that affect sleep preference.
“Most strikingly, they found that these variants consistently 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.
The study was published in Genome Biology and Evolution.
