Are you a morning person? You may be a Neanderthal descendant

Do you find it easy to wake up early? You may have Neanderthals in your ancestry.

A study published this week in Genome Biology and Evolution has found that Neanderthal DNA remains in some present-day humans and may determine whether someone is naturally an early riser.

Neanderthals are our closest extinct human relative, according to the Smithsonian’s National Museum of Natural History, and had defining physical features such as larger noses, angled cheek bones and stockier bodies. They were known to use sophisticated tools, control fire, be skilled in hunting, wear clothing and live in shelters.

A new study has found “morningness” has a lot to do with DNA.Credit: iStockphoto

“We found that Neanderthal DNA that remains in modern humans due to interbreeding has a significant and directional effect on modern humans,” study co-author Tony Capra, an associate professor of epidemiology and biostatistics at the University of California at San Francisco, wrote in an email. “In particular, the Neanderthal DNA that associates with chronotype consistently increases propensity to be a morning person.”

Migration to higher latitudes

As the ancestors of Eurasians – who now range in location from the British Isles to the mountains of Siberia – began to migrate out of Africa about 70,000 years ago, they were exposed to new environments at higher latitudes with more varied seasons, temperatures and levels of light exposure, the study said.

Those arriving to Eurasia interbred with the existing population, “initially with Neanderthals” and later with other ancestors such as Denisovans, who are now extinct, the study said. This created the potential for humans to gain genetic variants already adapted to these new environments.

“In higher latitudes there is more seasonal variation in light/dark cycles over the course of the year than in more equatorial latitudes,” Capra wrote.

It was “not immediately clear why increased morningness would be beneficial at higher latitudes,” though the study found that in present-day humans, “behavioural morningness” was linked to “a quickened pace of the circadian gene network”, which could be an advantage.

The discovery could help people better understand their sleep patterns today, as shift work and a reliance on screens and other technology can affect our innate sleeping habits.

Circadian rhythm changes

Our circadian rhythms are a natural guide for the body through the 24-hour cycle. They tell us when it’s time to eat, sleep and wake up.

Our circadian clock regulates our sleep and health.Credit: iStockphoto

They are “intrinsic” rhythms that adapt the biology of animals and plants to the Earth’s light-and-dark cycle, and are “regulated by a central circadian clock which is entrained to the environment” through light exposure, said Simon Archer, a professor of molecular biology of sleep at Britain’s University of Surrey.

Often when people have difficulties sleeping or staying awake, it’s because their circadian rhythms have gotten off-kilter because of health issues– including stress, depression, anxiety and hyperthyroidism – or shift work or travel.

Changes such as daylight saving time can also affect circadian rhythms which experts say is key to maintaining our sleep-wake cycles and overall health.

Sleep issues can lead to changes to metabolism and immunity that have been linked to health problems including cancer, heart disease and fatigue.

Some new technologies such as special masks, glasses, heart sensors and apps have been developed to help with these issues.

Circadian variants from Neanderthals

In this study, the researchers defined a set of 246 circadian-related genes and found hundreds of genetic variants with the potential to influence the circadian clock. Using artificial intelligence to analyse the genetic variants, they found it was possible that some humans could have obtained circadian variants from Neanderthals.

A Suited-up model of a Neanderthal man at the Neanderthal Museum, Germany.Credit: Holger Neumann

To test this, the researchers utilised a large cohort of several hundred thousand people, using the United Kingdom’s Biobank, a biomedical database. The study found “that these variants consistently increase morningness,” according to a statement about the study.

“I’m sure no one would have predicted that we’d actually see genetic evidence that some of us really are morning people,” Naomi Allen, professor in epidemiology at the UK Biobank wrote in an email. The findings come from “half a million volunteers sharing their de-identified genetic data, and researchers from around the world approaching it with such interesting questions,” she said of the collaboration.

A lot of our genetic ancestry from Neanderthals “was not beneficial and removed by natural selection,” the study said, but some aspects remain in human populations today and possibly “show evidence of adaptation”.

“The propensity to be a morning person could have been evolutionarily beneficial for our ancestors living in higher latitudes in Europe and thus would have been a Neanderthal genetic characteristic worth preserving,” the study said.

Having Neanderthal DNA in some parts of our genome may provide benefits such as in our immune systems, metabolism, and hair and skin, Capra wrote.

“We don’t think that being a morning person is actually what is beneficial, but that this is actually a signal of having a circadian clock that is more adaptable to changing light levels,” he said. “Having a faster-running clock also leads to rising earlier.”

“At higher latitudes it is beneficial to have a clock that is more flexible and better able to change to match the variable seasonal light levels,” he added.

“Intercrossing Sapiens may in some cases have obtained advantages,” for example, “allowing them to live in higher [latitudes] as shown here, but obviously also other advantages not examined in this study,” wrote Thomas Werge, a professor of clinical medicine at the University of Copenhagen and director of the Institute of Biological Psychiatry at the Copenhagen University Hospital, in an email.

Archer said the study was very interesting but “perhaps not too surprising” as “circadian clocks are an ancient evolutionary adaptation found in almost all organisms studied”, and that it would make sense that an adaptive advantage was selected and retained by our ancestors.

DNA may tell other stories such as variants that make some people sleep or wake later than others, Archer said: “For primates and our ancestors this may have provided a selective advantage in that not everyone is asleep at the same time”.

But, Archer said, in modern society “if you are an evening person there are potential associated risk factors” such as sleep deprivation, negative health, exposure to too much artificial light and poor diet.

But having traces of Neanderthal DNA is just one element that may determine your sleeping habits.

Capra clarified that “being a morning person is a very complex trait,” and hundreds of different genes as well as environmental and culture factors “strongly influence” it. “There are plenty of morning people who don’t have any of these Neanderthal variants!”

The Washington Post