If you reckon your early bird (or night owl) habits run in the family, it turns out the assumption might be more accurate than you’d expected. In fact, the trait could go way back to your Neanderthal ancestors.
In a paper published in Genome Biology and Evolution, scientists suggest that genes from our oldest relatives could be responsible for the way we sleep. Though many Neanderthal genes have been lost to the winds of evolution, , researchers think that for some people, their waking times might come straight from the Middle Paleolithic age.
“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,” the paper’s lead author, John Capra, an epidemiologist from the University of California, said.
“Then by analysing 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.”
What does that mean?
Only about 4% of human genes today come from Neanderthals. That’s because they’re a different species to modern humans, and while there was some crossover between the two, Neanderthal genes have mostly faded over time.
The researchers found out that modern humans and Neanderthals had different genes that affected people’s circadian rhythm, or “body clock.”
The scientists wanted to see if the Neanderthal variant, which is distinct, could exist in some modern humans.
So, they checked the UK’s Biobanks, which has genetic and lifestyle information on more than 500,000 people.
They found that not only did plenty of people still carry the Neanderthal variant, but they also discovered that those with the gene tended to be morning people.
Why?
The researchers suggest that it could be due to the light and lifestyles in which Neanderthals lived. It’s not so much that getting up early was good for Neanderthals, they say ― but adapting quickly to changing light levels could have been helpful.
“We don’t think that being a morning person is actually what was beneficial. Rather, we think it is a signal of having a faster running clock that is better able to adapt to seasonal variation in light levels,” John Capra said (via The Guardian).
“Now we have genetic evidence that some of us really are morning people,” Mark Maslin, a professor of Geography at University College London, who wasn’t involved in the study, said.
“When humans evolved in tropical Africa, the day lengths were on average 12 hours long. Now hunter-gatherers spend only 30% of their awake time collecting food, so 12 hours is loads of time.
“But the further north you go, the shorter and shorter the days get in winter when food is particularly scarce, so it makes sense for Neanderthals and humans to start collecting food as soon as there is any light to work by.”
Of course, not every morning person will have the Neanderthal influence, and not everyone with the ancient gene will be a morning person.
“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,” Capra shared.