Modern human biological clocks linked to prehistoric ancestors
Scientists have discovered that genes inherited from our prehistoric Neanderthal relatives increase our tendency to wake up early – which is useful in regions with short winter days .
People who go to bed early and rise early may have their ancient ancestors to thank for this habit &ndash ; or, at least, the Neanderthals with whom their ancestors produced offspring, scientists say.
According to The Guardian, researchers have found that DNA inherited from our thick-browed cousins may contribute to some people's tendency to be early risers, making them more comfortable getting up and going to bed earlier than others.
B While most of the genes that modern humans acquired through ancient interbreeding were weeded out by evolution, a small portion remained, most likely because they helped early modern humans adapt to their new environment as they left Africa for Eurasia.
“By analyzing fragments of Neanderthal DNA that were preserved in the genomes of modern humans, we discovered a striking trend,” says John Capra, an epidemiologist at the University of California, San Francisco. According to him, many of them influenced the genes that control the biological clock of modern humans, in most cases “increasing the tendency to be a morning person.”
Waves of Homo sapiens migrated from Africa to Eurasia about 70,000 years ago, writes The Guardian. Upon arrival, they encountered Neanderthals, who had already adapted to life in a colder climate, having occupied the territory hundreds of thousands of years ago. Thanks to interbreeding between groups, humans living today carry up to 4% Neanderthal DNA, including genes associated with skin pigmentation, hair and immunity.
John Capra and his colleagues analyzed the DNA of modern humans and Neanderthals and found that different genetic variants were involved in the biological clocks, or circadian rhythms, of the two groups. Because the ancestors of modern humans mated with Neanderthals, it is possible that some people alive today carry Neanderthal variants, the scientists reasoned.
To test this, the researchers turned to the British Biobank, which stores genetic information , information about the health and lifestyle of half a million people. Not only were many people carriers of the variants, but the genes were consistently associated with early waking, the scientists wrote in Genome Biology and Evolution.
But you don't need Neanderthal genes to be a morning person. Hundreds of different genes influence when people sleep and wake up, and there are many environmental and cultural factors. Overall, Neanderthal genes have only a small impact.
Capra suspects that many modern humans carry Neanderthal genes because they helped their ancestors adapt to life at higher latitudes. “We don't think being a morning person was actually helpful. Rather, we think it signals faster clocks that are better able to adapt to seasonal variations in light levels, says Capra. – At higher latitudes, it is useful to have clocks that are more flexible and better able to adjust to changing seasonal light levels.
Professor Mark Maslin from University College London, who was not involved in the study, comments: &ldquo ;We now have genetic evidence that some of us are indeed early risers. When humans evolved in tropical Africa, days averaged 12 hours. Nowadays, hunter-gatherers only spend 30% of their waking time gathering food, so 12 hours is a lot of time. But the further north you go, the shorter the days become in winter, when food is especially scarce, so it makes sense for Neanderthals and humans to start gathering food as soon as there is some light to work with.
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