Scientists suggest that individuals who have a tendency to go to sleep and wake up early may owe their habit to their early human predecessors, particularly the Neanderthals with whom their ancestors interbred.

Researchers have discovered that DNA passed down from our ancestors with prominent brows could potentially play a role in causing certain individuals to have a natural inclination towards being early risers, making it easier for them to wake up and go to sleep earlier compared to others.

Although many of the genes acquired through interbreeding in our ancient past have been eliminated through evolution, there are still a few that have persisted. This is likely due to their role in aiding early modern humans in adapting to their new surroundings when they migrated from Africa to Eurasia.

John Capra, an epidemiologist at the University of California in San Francisco, revealed that through examining the fragments of Neanderthal DNA still present in present-day human genomes, a significant pattern emerged. He noted that a large portion of these fragments impacted the genes responsible for regulating our internal body clocks, ultimately leading to an increased likelihood of being a morning person.

Around 70,000 years ago, groups of Homo sapiens migrated from Africa to Eurasia. Upon reaching their destination, they came into contact with the Neanderthals, who had already been living in the region for hundreds of thousands of years and had adapted to the colder climate. Through interbreeding, modern humans now carry up to 4% of Neanderthal DNA, which includes genetic traits related to skin color, hair, fat distribution, and immunity.

Capra and his team studied the DNA of present-day humans and Neanderthals and discovered that distinct genetic variations play a role in their body clocks, or circadian rhythms. As modern humans interbred with Neanderthals, it was plausible that contemporary humans may possess the Neanderthal variants, the researchers hypothesized.

The scientists utilized UK Biobank, a database containing data on 500,000 individuals’ genetics, health, and lifestyle, to verify their findings. They discovered that a significant number of individuals possessed the genetic variations and that these genes were consistently associated with being an early riser, according to their publication in Genome Biology and Evolution.

But being a morning person doesn’t require Neanderthal genes. Hundreds of different genes affect when people sleep and wake up, and there are plenty of environmental and cultural influences too. Overall, the Neanderthal genes have only a small impact.

Capra believes that a significant portion of modern humans possess Neanderthal DNA due to its advantageous role in their ancestors’ adaptation to living in regions with higher latitudes. According to Capra, the advantage is not necessarily being a morning person, but having a faster internal clock that can better adjust to changes in light levels throughout the year. This flexibility is especially beneficial in areas with higher latitudes where seasonal light levels vary.

Professor Mark Maslin, from University College London and not associated with the research, stated: “There is now genetic proof that certain individuals are indeed morning people.”

During the time when humans first evolved in tropical Africa, the typical length of a day was 12 hours. However, modern hunter-gatherers only spend about 30% of their waking hours gathering food, leaving them with plenty of time. As one moves further north, the winter days become shorter and shorter, making it even more crucial for Neanderthals and humans to begin foraging as soon as there is any light available.

Source: theguardian.com