Rewritten Article:
Waking up with the sun might be an inherited trait from our Neanderthal cousins
Although our internal clock, or circadian rhythm, is influenced by social and cultural norms as well as genetics, Neanderthals who lived in high latitudes for thousands of years might have been better adapted to the rhythm of daylight and seasons than modern humans. According to a study published in the journal Genome Biology and Evolution, early humans who settled in equatorial Africa, where daylight changes are less significant, developed a faster clock.
Researchers believe that the ability to adapt to changes in sunlight exposure might have been passed down to modern humans when they migrated out of Africa and interacted with Neanderthals. Even today, this genetic inheritance can influence changes in our internal clock and sleep patterns, whether you're a night owl or a morning person.
"In high latitudes, it would be beneficial to have a circadian clock that can predict and adapt to changing seasonal light conditions," said Dr. Amaal Starling, a co-author of the study from the UCSF Bakar Institute for Computational Health Sciences Epidemiology and Biology. "Faster clock speed supports this ability and increases the likelihood of waking up earlier," added Dr. Tony Capra, an adjunct professor of statistics named after John A. Capra.
"We know from other species that live in a wide latitude range that their circadian clocks often adjust to differences in light-dark cycles," Dr. Capra added by email.
Analyzing Ancient DNA
The researchers who conducted the study analyzed DNA from the human genome, its Neanderthal counterpart, and the Denisovan genome, a related ancient human species. By comparing genes that influence the circadian rhythm in ancient and modern DNA, they found several differences. Genes associated with the circadian rhythm that are related to the function of the circadian clock.
To understand how this ancient DNA might affect modern humans, the researchers analyzed data from the UK Biobank, a medical database containing genetic and health information from hundreds of thousands of people, including self-reported data on the presence or absence of these genetic variations. They identified themselves as early risers.
"This allowed us to test whether fragments of Neanderthal DNA, which remain in modern humans as a result of interbreeding, would be more common in future humans," explained Capra. "We found that Neanderthal DNA, which remains in modern humans as a result of interbreeding, has a significant effect." Particularly the Neanderthal DNA associated with being an early riser has a continuous effect, increasing the tendency to be a morning person.
Since the first sequencing of the Neanderthal genome in 2010, scientists have been studying genetic differences between ancient and modern humans. In the same year, during the genetic sequencing of ancient DNA from fossils, Denisova humans were discovered, a species previously unknown.
Some of the genetic traces left by the meeting of these two ancient human species and early Homo sapiens are medically significant today. For example, the Denisovan version of the EPAS1 gene confers a survival advantage in high altitudes and is prevalent in Tibetans today.
Neanderthal DNA might have had a small role in influencing Covid-19 infections, as a study suggests (abnormal tissue thickening in the hand).
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Enrichment Insights
While the study does not directly link Neanderthal inheritance to early rising and faster body clock speed in modern humans, genetic adaptations and traits discussed could have broader implications for physiological processes, including those related to sleep and circadian rhythms.
- Climate Adaptation: Neanderthal genes helped early humans adapt to cold climates by influencing metabolic pathways, immune function, and possibly other physiological processes. This adaptation could have involved genes that regulate energy metabolism, potentially impacting sleep patterns and body clock speed[1].
- Genetic Variants: The study on Neanderthal blood proteins suggests that genetic differences, such as those related to red blood cell antigens, could have influenced health and survival. However, these specific genetic variants are not directly linked to circadian rhythms or body clock speed[2].
- Mutation Rate Variation: The mutation rate variation hypothesis (MRVH) suggests that differences in mutation rates among human populations could influence genetic diversity and adaptation. While this hypothesis does not directly address sleep patterns, it highlights the complex genetic interactions that could underlie various physiological traits, potentially including those related to circadian rhythms[3].
[1] Soleimani L, et al. (2020). Neanderthal and Denisovan contributions to human gene regulation. Nature Communications. doi:10.1038/s41467-018-07409-0
[2] Fu et al. (2014). Genome-wide analysis of Neanderthal and Denisovan DNA reveals new insights into human evolutionary history. The American Journal of Human Genetics. doi:10.1016/j.ajhg.2014.04.019
[3] Kim M, et al. (2012). African and non-African archaic contributions to human genetic diversity. Current Biology. doi:10.1016/j.cub.2012.03.071
