A new paper has been published in a magazine Genome biology and evolutionAccording to a paper published by Oxford University Press, genetic material from Neanderthal ancestors may have contributed to the tendency of some people today to be “early risers” – the type of people who find it easier to get up early and go to bed. I discovered that there is a possibility that

Human evolution and genetic adaptation

All anatomically modern humans trace their origins to Africa about 300,000 years ago, where environmental factors shaped many of their biological characteristics. About 70,000 years ago, the ancestors of modern Eurasian humans began migrating into Eurasia, where they encountered a variety of new environments, including high latitude regions with large seasonal fluctuations in sunlight and temperature.

But other hominins, such as Neanderthals and Denisovans, lived in Eurasia for more than 400,000 years. These archaic humans diverged from modern humans about 700,000 years ago, and as a result, our ancestors and archaic humans evolved under different environmental conditions. This led to the accumulation of strain-specific genetic variation and phenotypes. When humans came to Eurasia, they interbred with archaic humans from the continent. This created the possibility for humans to acquire genetic variations already adapted to these new environments.

Genes of ancient humans and characteristics of modern humans

Although previous studies have shown that many of the archaic ancestors of modern humans are not beneficial and have been removed by natural selection, some archaic hominin variants that remain in human populations has shown evidence of adaptation. For example, archaic genetic variation is thought to be associated with differences in hemoglobin levels, immune resistance to new pathogens, levels of skin pigmentation, and fat composition among Tibetans at high altitudes.

Changes in patterns and levels of light exposure have biological and behavioral effects that lead to evolutionary adaptations. Scientists have extensively studied the evolution of circadian adaptations in insects, plants, and fish, but humans have been less well studied. The Eurasian environment where Neanderthals and Denisovans lived for hundreds of thousands of years is located at higher latitudes and has more variable daylight hours than where modern humans evolved before leaving Africa. So the researchers investigated whether there was genetic evidence for differences in circadian clocks between Neanderthals and modern humans.

Research methods and findings

The researchers defined a set of 246 circadian genes using a combination of literature searches and expert knowledge. They found hundreds of genetic variations unique to each strain that can affect genes involved in the circadian clock. Using artificial intelligence techniques, they identified 28 circadian genes that contain mutations that could alter splicing in archaic humans and that may be differentially regulated between modern and archaic humans. identified 16 circadian genes.

This indicates that there may be functional differences between the circadian clocks of ancient and modern humans. Eurasian modern humans and Neanderthal ancestors interbred, so some humans may have acquired circadian variation from Neanderthals.

To test this, the researchers studied a large population of hundreds of thousands of people in the UK Biobank and found that introgressed genetic mutations (mutations that passed from Neanderthals to modern humans) could affect wakefulness and sleep. We investigated whether there is a relationship with physical preference for. They discovered a number of introgressed mutants that affected sleep preferences, and most surprisingly, they found that these mutants consistently increased morningness, or the tendency to rise early. This suggests a directional influence on this trait and is consistent with adaptations to high latitudes observed in other animals.

Increased morning time in humans is associated with a shortened circadian clock period. This may be beneficial at high latitudes, as it has been shown that sleep and wakefulness can be coordinated more quickly with external timing cues. Shortening of the circadian period is required to synchronize with the long summer light period at high latitudes in Drosophila, and selection for a shorter circadian period results in the latitudinal period decreasing with increasing latitude in natural Drosophila populations. There is a latitudinal gradient in which the

Therefore, the bias toward morningness in introgressed mutants may indicate selection for shortened circadian periods in populations living at high latitudes. The tendency to be a morning person may have been evolutionarily beneficial to our ancestors who lived in the high latitudes of Europe, and would have been a Neanderthal genetic trait worth preserving.

“By combining ancient times, DNA“After extensive genetic and artificial intelligence research in modern humans, we discovered substantial genetic differences in the circadian systems of Neanderthals and modern humans,” said John, lead author of the paper.・A. Capra said.

“And by analyzing Neanderthal DNA fragments that remain in the genomes of modern humans, we discovered surprising trends, many of which affect the regulation of circadian genes in modern humans. These effects are primarily in the consistent direction of increasing Neanderthal tendencies.” Morning people. This change is consistent with the effects of living at high latitudes on animals’ circadian clocks, which may allow them to adjust more quickly to changing seasonal light patterns.

“Our next steps include applying these analyzes to more diverse modern human populations and investigating the effects of the Neanderthal variants we identified on circadian clocks in model systems. and applying similar analyzes to other potentially adaptive traits.”

Reference: “Archaic Introgression Shaped Human Circadian Traits” by Keila Velazquez-Arcelay, Laura L Colbran, Evonne McArthur, Colin M Brand, David C Rinker, Justin K Siemann, Douglas G McMahon, John A Capra, December 14, 2023 , Genome biology and evolution.
DOI: 10.1093/gbe/evad203