Some people today might be early risers because of DNA they take after Neanderthals tens of thousands of years ago, suggests new research.

When early humans migrated from Africa to Eurasia roughly 70,000 years ago, some of them mated with Neanderthals, who had already adapted to the colder, darker climates of the north. The ripple (涟漪) effects of that intermating still exist today: Modern humans of non-African ancestry (血统) have between 1 and 4 percent Neanderthal DNA. Some of that DNA relates to sleep more specifically, the internal body clock known as the circadian rhythm.

For the new study, researchers compared DNA from today’s humans and DNA from Neanderthal fossils (化石). In both groups, they found some of the same genetic variants involved with the circadian rhythm. And they found that modern humans who carry these variants also reported being early risers.

For Neanderthals, being “morning people” might not have been the real benefit of carrying these genes. Instead, scientists suggest, Neanderthals’ DNA gave them faster, more flexible internal body clocks, which allowed them to adjust more easily to annual changes in daylight. This connection makes sense in the context of human history. When early humans moved north out of Africa, they would have experienced variable daylight hours — shorter days in the winter and longer days in the summer-for the first time. The Neanderthals’ circadian rhythm genes likely helped early humans’ offspring (后代) adapt to this new environment.

Notably, the findings do not prove that Neanderthal genes are responsible for the sleep habits of all early risers. Lots of different factors beyond genetics can contribute, including social and environmental influences. The study also only included DNA from a database called the U.K. Biobank—so the findings may not necessarily apply to all modern humans. Next, the research team hopes to study other genetic databases to see if the same link holds true for people of other ancestries. If the findings do apply more broadly, they may one day be useful for improving sleep in the modern world, where circadian rhythms are disturbed by night shifts and glowing smartphones.

Different people enjoy different amounts (数量) of human contact. While some adore making lots of friends, others prefer plenty of time on their own. However, is there such a thing as too much time alone? And how does isolation (孤独) affect humans?

In April, a Spanish athlete named Beatriz Flamini came out of a cave where she had spent 500 days as part of a study on social isolation. During her time 70 metres underground, Flamini had no human contact at all. However, she did record videos of herself and was monitored continually by scientists.

Doctors measuring the effects of isolation are building up a picture of how it can change the way people experience the passing of time, and how it affects the body’s natural clock. Flamini first entered the cave on 20 November 2021, but she lost track of time 65 days later. During her time underground, she sometimes experienced auditory hallucinations, which means that she was hearing noises that weren’t there. The isolation affected her balance when she came out of the cave, and she also had to get used to being in sunlight.

Isolation studies are important for planning for long-lasting space tasks. Although astronauts (宇航员) often work with other members, the teams are small and their living quarters are small, too. For example, the astronaut Kjell Lindgren spent 141 days on board the International Space Station with never more than five teammates for company. This summer, four volunteers will start a year of living inside a big box, as part of NASA’s Crew Health and Performance Exploration Analog. The aim of this experiment is to find out how astronauts will manage extreme isolation and stay healthy while living on Mars.

Scientists have known for decades that having measles suppresses(抑制) kids’ immune systems for several weeks or months, leaving them ill-equipped to fight off pneumonia, bronchitis and other infections.

Now a team of researchers has suggested that the measles virus may also leave a longer-lasting sort of “immune-amnesia” that makes it harder for people to stave off other illnesses for two years or more.

That re-emphasizes the importance of vaccination(接种疫苗), said biologist Michael Mina, lead author of a paper that was published in the journal Science.

“There may be a long-lasting impact that you can’t undo if your child gets measles,” he said. “I hope this study can impress upon people the danger measles poses.”

The researchers used what Mina called “an unconventional approach” to search for the long-lasting immune system effects. Previous work in monkeys suggested that monkeys with the disease lost white blood cells their bodies had trained to fight off other illnesses, leaving them more likely to be infected.

To test if a similar thing may occur in humans, the group mined historical data to find out the relationship between measles incidence(发病率) and deaths from other infectious diseases.

They turned to data from England and Wales—developed nations where disease levels are generally low, allowing a less-confused view of measles’ effects. Studying measles incidence and deaths from infectious disease both before and after the introduction of the measles vaccine in the U.K. in the 1960s, Mina and the team saw a sort of shadow effect, where deaths from a variety of non-measles infectious diseases closely tracked measles incidence. The more measles in a population, the more deaths from other illnesses in the 28-month period that followed.

“Really it didn’t matter what age group, what decade or what country,” said Mina. “They all showed consistent results… what we’re suggesting happens over the long term is that your immune system works fine, but it has forgotten what it previously learned.”

Some researchers who were not involved in the work questioned whether the reductions in deaths as measles cases declined may have had more to do with improving nutrition and smaller family size than with prolonged immune suppression.

Others thought the paper’s opinion of years-long suppression was seemingly reasonable but said they could not comment on the mathematical models the group used.

To know for certain what was behind the effect the group saw, Mina agreed, scientists would need to look at immune cells and observe their behavior. He said he would like to push the work in a more traditional direction: back into the laboratory.