A recent study suggests that Neanderthal and Denisovan DNA might contribute to early-rising habits in some individuals, surprising researchers with unexpected findings. The genes passed on by these ancient human relatives seem to enhance "morningness" and persist in modern human populations, says Tony Capra of the University of California, San Francisco.
The study, titled "Archaic Introgression Shaped Human Circadian Traits" published in the peer-reviewed journal Genome Biology and Evolution, proposes that Neanderthals and Denisovans developed these genetic mutations due to prolonged exposure to cold, dark environments, a hypothesis that requires further investigation.
Swedish paleogeneticist Svante Paabo, who sequenced the genome of the Neanderthal and discovered the previously unknown hominin Denisova, won the Nobel Medicine Prize.
Ancient DNA Shapes Circadian Rhythms in Modern Humans
Majority of modern human DNA traces back to Homo sapiens in Africa, but along the evolutionary path, some ancestors assimilated genetic material from extinct human lineages like Neanderthals and Denisovans.
Although much of this genetic diversity has diminished over time, individuals of European and Asian descent retain around 2% Neanderthal DNA, while Papua New Guineans harbor approximately 5% Denisovan DNA.
Having migrated out of Africa hundreds of thousands of years earlier than modern humans' direct ancestors, Neanderthals and Denisovans had more time to adapt their genes to the colder, darker climates of Western and Northern Eurasia. The period when Homo sapiens confronted such weather conditions began roughly 50,000 to 60,000 years ago during a significant migration into Europe.
In this context, genetic mutations passed down by Neanderthals and Denisovans may have provided certain individuals with advantages in coping with the harsh Eurasian winter months.
To investigate whether these genetic variations influenced circadian rhythms, Tony Capra and his team at the University of California, San Francisco, compared the genomes of Neanderthals and Denisovans with those of modern-day humans from the UK Biobank. They identified over a thousand shared mutations, some of which had previously been associated with regulating the human body clock.
Analyzing questionnaire responses from individuals in the biobank, the researchers found that those with these mutations were more likely to consider themselves early risers. This unexpected correlation between ancient DNA and morning habits marked a significant and exciting discovery in the study.
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Further Validation and Deeper Exploration Needed
Despite its promise, the study's link between genes and behaviors should be approached cautiously, as Biobank studies indicate associations rather than definitive connections, necessitating further experimental validation.
The intricate nature of how the human body regulates metabolism raises uncertainties about whether carrying a specific mutation guarantees one's inclination to be a morning person, as multiple factors are often at play, as highlighted by Capra and his research team.
Joshua Akey from Princeton University underscores the need for a more detailed investigation, recognizing the compelling case made by the authors.
Further studies involving lab-engineered human cells with Neanderthal and Denisovan body clock mutations could shed light on their behavioral impact, according to Michael Dannemann, an evolutionary geneticist at the University of Tartu in Estonia. This approach could not only enhance our understanding of living human DNA but also contribute valuable insights into Neanderthal biology.
Research on genetic distinctions between ancient and modern humans, initiated in 2010 with the sequencing of the Neanderthal genome, has unveiled medical relevance. Denisovan genes, such as the EPAS1 gene linked to high-altitude survival, bear implications for contemporary health.
Similarly, Neanderthal DNA is implicated in influencing COVID-19 infection and conditions like Duputytren's disease, emphasizing the enduring impact of ancient genetic encounters on modern health.
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