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taylorvich [soylentnews.org] writes:

https://phys.org/news/2023-12-neanderthals-morning-people.html [phys.org]

A new research paper finds that genetic material from Neanderthal ancestors may have contributed to the propensity of some people today to be "early risers," the sort of people who are more comfortable getting up and going to bed earlier.

The findings are published in the journal Genome Biology and Evolution.

All anatomically modern humans trace their origin to Africa around 300,000 years ago, where environmental factors shaped many of their biological features. Approximately 70,000 years ago, the ancestors of modern Eurasian humans began to migrate out to Eurasia, where they encountered diverse new environments, including higher latitudes with greater seasonal variation in daylight and temperature.

But other hominins, such as the Neanderthals and Denisovans, had lived in Eurasia for more than 400,000 years. These archaic hominins diverged from modern humans around 700,000 years ago, and as a result, our ancestors and archaic hominins evolved under different environmental conditions. This resulted in the accumulation of lineage-specific genetic variation and phenotypes. When humans came to Eurasia, they interbred with the archaic hominins on the continent, and this created the potential for humans to gain genetic variants already adapted to these new environments.
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The Eurasian environments where Neanderthals and Denisovans lived for several hundred thousand years are located at higher latitudes with more variable daylight times than the landscape where modern humans evolved before leaving Africa. Thus, the researchers explored whether there was genetic evidence for differences in the circadian clocks of Neanderthals and modern humans.
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This indicated that there were likely functional differences between in the circadian clocks in archaic hominins and modern humans. Since the ancestors of Eurasian modern humans and Neanderthals interbred, it was thus possible that some humans could have obtained circadian variants from Neanderthals.

To test this, the researchers explored whether introgressed genetic variants—variants that moved from Neanderthals into modern humans—have associations with the preferences of the body for wakefulness and sleep in large cohort of several hundred thousand people from the UK Biobank.

They found many introgressed variants with effects on sleep preference, and most strikingly, they found that these variants consistently increase "morningness," the propensity to wake up early. This suggests a directional effect on the trait and is consistent with adaptations to high latitude observed in other animals.

Original Submission