"Early risers" can thank the Neanderthal genes in their DNA

A study that links Neanderthal genes to modern “early risers” is shredding new light on the mystery of human sleep patterns and their origins. The research delves into the genetic journey from our African roots to intermingling with Neanderthals, and uncovers a fascinating link between ancient genes and today’s sleep preferences.

About 300,000 ago, anatomically modern humans emerged in Africa with evolving traits that were molded by their environment. Fast forward to 70,000 years ago, these humans ventured into Eurasia, encountering not just varied landscapes but also other hominins like Neanderthals and Denisovans. 

These archaic hominins, which diverged from our lineage around 700,000 years ago, had already adapted to the Eurasian environment over 400,000 years.

Humans and neanderthal genes

When modern humans reached Eurasia, they didn’t just coexist with Neanderthals and Denisovans – they interbred. This intermingling was more than a social exchange. It was also a genetic one, providing humans with variants well-suited to their new environment. 

While much of the archaic hominin ancestry was lost to natural selection, certain traits proved advantageous, contributing to adaptations like altitude-friendly hemoglobin levels, immune responses, skin pigmentation, and fat composition.

Beyond physical traits, the researchers identified 246 circadian genes. These genes, integral to our body’s internal clock, showed significant variances between lineages, hinting at functional differences in how archaic hominins and modern humans perceived day and night cycles.

The discrepancy in circadian rhythms makes sense when you consider the varying daylight patterns in Africa and higher Eurasian latitudes. It also raises the question: did Neanderthal genes influence our sleep-wake preferences?

Neanderthal genes and mornings

Using artificial intelligence, the researchers pinpointed 28 circadian genes in archaic humans with potential alterations in splicing, alongside 16 genes with divergent regulations. This suggested functional differences in circadian rhythms between us and our ancient cousins.

In a comprehensive study involving hundreds of thousands of individuals from the UK Biobank, the experts discovered a striking correlation. They found that introgressed genetic variants from Neanderthals were consistently linked to increased morningness. This propensity to wake up early aligns with adaptations seen in animals living in high latitudes.

Morningness in humans, associated with a shortened circadian clock, likely offered a survival edge in higher latitudes. This adaptation mirrors what is observed in fruit flies, where shortened circadian periods are crucial for synchronization with extended summer daylight. 

Thus, the morningness trait, potentially a Neanderthal legacy, might have been an evolutionary boon for our ancestors in Europe.

Research implications and future study

This study offers a compelling glimpse into how our ancient encounters have shaped not just who we are, but how we live and when we prefer to wake up. 

In the grand narrative of human evolution, it appears our Neanderthal ancestors might have left us more than just tools and fire – they might have set our alarm clocks.

“By combining ancient DNA, large-scale genetic studies in modern humans, and artificial intelligence, we discovered substantial genetic differences in the circadian systems of Neanderthals and modern humans,” said study lead author John A. Capra. 

“Then by analyzing the bits of Neanderthal DNA that remain in modern human genomes we discovered a striking trend: many of them have effects on the control of circadian genes in modern humans and these effects are predominantly in a consistent direction of increasing propensity to be a morning person. This change is consistent with the effects of living at higher latitudes on the circadian clocks of animals and likely enables more rapid alignment of the circadian clock with changing seasonal light patterns.” 

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

Interaction between Neanderthals and Homo Sapiens

The intricate tapestry of human history becomes even more fascinating when we consider the interactions between Homo sapiens (modern humans) and Neanderthals. As discussed above, this interspecies connection played a significant role in shaping the course of human evolution and have left a lasting impact on the genetic makeup of modern humans.

Evidence of Neanderthal-human interplay

Archaeological sites have revealed significant insights into the interactions between humans and Neanderthals. Tools, cave paintings, and remains found in locations such as the Neander Valley in Germany and other parts of Europe suggest that these two species coexisted for several thousand years.

The nature of the artifacts indicates that there were likely shared practices in tool-making and possibly hunting strategies.

As discussed previously in this article, genetic studies have been pivotal in understanding the extent of interaction between humans and Neanderthals. The presence of Neanderthal DNA in the modern human genome is conclusive evidence of interbreeding.

Approximately 1-2% of the DNA in non-African modern humans can be traced back to Neanderthals. This genetic exchange suggests that there was not only interaction but also integration to some extent.

Nature of their interactions

The coexistence of humans and Neanderthals in overlapping territories likely led to competition for resources. This competition might have been a driving force for the eventual decline of Neanderthals. However, it also fostered a scenario where the two species had to adapt and perhaps learn from each other.

Evidence such as the similarity in tool-making techniques and burial rituals suggests there was some level of cultural exchange between humans and Neanderthals. These interactions might have ranged from hostile encounters to peaceful exchanges and even collaboration in certain activities.

Mixing Neanderthal and human genes

Interbreeding between humans and Neanderthals is the most direct form of interaction. This genetic mixing had implications for the evolution of modern humans, contributing to traits related to the immune system and possibly other physiological and cognitive aspects.

In summary, the interactions between humans and Neanderthals were complex and multifaceted, involving competition, cultural exchanges, and interbreeding. These interactions played a significant role in shaping the course of human evolution and have left a lasting impact on the genetic makeup of modern humans. Ongoing research continues to unveil more about this fascinating chapter in human history.

The study is published in the journal Genome Biology and Evolution.

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