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If you are a morning person, chances are that it is because of your pre-historic ancestors: Scientists found that DNA inherited from Neanderthals could be linked to sleeping habits and rising early, the Guardian reported.
The Neanderthals were cousins of the Homo sapiens species that currently exist as modern humans, which went extinct around 40,000 years ago after coexisting with Sapiens for tens of thousands of years.
About 70,000 years ago, groups of Homo sapiens left Africa for Eurasia, where Neanderthals were already settled. Interbreeding between the two species provided modern-day humans with up to 4 percent Neanderthal DNA, predominantly impacting skin pigmentation, hair and immunity.
Most of the Neanderthal genes were eliminated as humans evolved throughout the centuries. What was retained helped them survive in new areas with different climates and, crucially, daylight periods.
In Africa, around the Equator, days last on average 12 hours, and variations are minimal. North, in Eurasia, however, days are shorter in winter. At the time of the Neanderthals, this meant they had to be awake for as long as they had daylight to find food.
Genetically, this led to modifications in body clocks, also known as circadian rhythms, making them more flexible. It prompted our ancestors’ cousins to sleep and wake up early.
By comparing the DNA of Neanderthals and modern humans, the researchers found variants impacting circadian rhythms and argued that humans may have received them from the Neanderthals their ancestors mated with. They also found that these variants were consistently linked with the habit of waking up early.
However, being an early bird does not necessarily mean having Neanderthal ancestry. The genes found in this study are part of a greater set of genes affecting body clocks. The environment and cultural practices also play a role.