Are you a morning person? A study suggests that your ancestors had “good” genes
A recent scientific study suggests that the genetic heritage of Neanderthal predecessors may influence the tendency of some modern individuals to be “morning people,” meaning more inclined to wake up and go to bed early.
All anatomically modern humans trace their origin back to Africa approximately 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 to Eurasia, encountering new and different environments, including higher latitudes with greater seasonal variations in daylight and temperature.
Past research has shown that many inherited features from ancient hominids in modern humans proved non-advantageous and were eliminated by natural selection. However, some of these ancient characteristics that persisted in human populations show signs of adaptation. For example, certain ancient genetic variants are linked to differences in hemoglobin levels in Tibetan populations living at high altitudes, immune resistance to new pathogens, skin pigmentation, and fat composition. Changes in light exposure can have biological and behavioral effects leading to evolutionary adaptations. Scientists have extensively studied how insects, plants, and fish have adapted to the evolution of their circadian rhythms, but this phenomenon has not been fully understood in humans yet.
The Eurasian environments where Neanderthals and Denisovans lived for several hundred thousand years are at higher latitudes with more variable daytime hours compared to the landscape where modern humans evolved before leaving Africa. Therefore, researchers explored whether there were genetic evidence for differences in the circadian clocks of Neanderthals and modern humans. A circadian clock is the biological clock that each of us has, regulating the alternation between sleep and wakefulness, cyclically repeating every 24 hours.
Analyzing various genetic variants, researchers found many variants with effects on sleep preference, and, more surprisingly, they discovered that these variants consistently increase the tendency to wake up early. This suggests a directional effect on the trait and is consistent with adaptations to high latitudes observed in other animals. Therefore, the inclination to be an early riser in these variants may indicate selection toward a shortened circadian period in populations living at high latitudes. The propensity to be a morning person could have been evolutionarily beneficial for our ancestors living at higher latitudes in Europe and, therefore, might have been a genetic trait of Neanderthals worth preserving.
