Humans may have evolved to need less sleep

Some animals seem to live well on little sleep

African bush elephants typically sleep for about 2 hours per 24-hour day, coming in well under a human's recommended seven-hour minimum. Other animals also appear to skimp on sleep, by human standards, without the consequences humans associate with being sleep deprived. This academic article details the sleeping habits of animals that appear to thrive on fewer than 40 winks and explores whether their sleep processes are just built different.

The REM cycle happens around four to six times per night

Sleep is a natural process that is critical to maintaining life—a process conserved throughout evolution across just about any animal with a brain. Generally speaking, the first three stages involve increasingly deep phases of non-REM sleep, followed by a roughly 90-minute period of REM sleep that repeats throughout the night.

Similarities between human and animal sleep

Have you ever noticed the wide-ranging differences in sleep between humans and animals? Sleep as a necessity is present amongst all animal species, but the specific patterns of sleep vary widely. Just think of the differences between how an owl, a whale, and a horse might sleep. This helpful resource from the Sleep Foundation explores the relations between human and animal sleep, complete with some fascinating statistics about sleep patterns throughout the animal kingdom!

The lost medieval habit of 'two sleeps'

While most people accept a single seven-to-nine-hour nightly slumber is ideal, the approach is a relatively modern idea. For centuries, interrupted sleep was the norm, with historians uncovering descriptions of two periods of sleep during the normal 24-hour cycle.

What sleep is for and why you can’t live without it

Sleep is one of the most important needs that humans have. The body uses sleep as a time of restoration and rejuvenation, as body tissues repair themselves, growth hormones are released, and the process continues. Brain plasticity theorists believe that sleep is also used for the processing and consolidating of new memories.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

How much sleep do you need?

When it comes to how much sleep you need, age matters—and, for your health, it's important to be well rested. Young children between the ages of one and three need the most sleep: It’s recommended that toddlers get between 11 and 14 hours of...

Why don't humans hibernate?

Hibernation is a superpower in the animal world that allows certain species to time travel from difficult times to abundance. This essay in Aeon explains this helpful natural process and why humanity's technological advancements may have hindered our ability to participate in the practice. Learn about the rising interest in human hibernation as a result of modern adversity, and if it could potentially become a reality.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

Circadian rhythms shift as we age—making older adults want to go to bed earlier

Throughout our lives our internal biological clocks shift. Early-to-rise toddlers become hard-to-wake teens and eventually early-to-sleep seniors. Circadian rhythm fluctuations throughout our life cycle explain some of these changes.

Why you should work 4 hours a day, according to science

Some of history's luminaries worked just four hours a day, including literary great Charles Dickens and biologist Charles Darwin. Observers suggest such a short period forces intense focus sustained by extended rest. In contemporary work, the high premium placed on the number of hours worked can overlook the importance of rest.

The human brain only uses 5% more energy during active tasks versus resting

Despite only being 2% of the weight of a human body, the average adult brain consumes 20% of its energy, with the majority of it spent on maintaining homeostasis—the stable equilibrium conditions of temperature, acidity, blood sugar, and other properties in the body. For infants, the consumption is closer to 50%.

The 4% DNA difference between humans and chimps

On the genetic level, we’re not all that different from chimps. But those small differences in DNA can have huge effects. This 11-minute video digs in to the topic.

Humans won't develop more than 5 fingers because it would impact too many body parts

All modern animals have five or fewer digits on each of their limbs. Roughly 348 million years ago, at least two species had eight: the Ichthyostega and the Acanthostega. According to Dollo's law, complex evolved features are very unlikely to recur in evolution. Researchers believe humans won't develop more than five digits because it would impact other body parts too much.

Humanity's reduced body hair slows down wound healing

Cuts to human skin take twice as long to heal compared to chimps and other mammals. Scientists argue this is due to the reduced number of hair follicles on human bodies. Hair follicles contain stem cells which help repair skin cells faster, so as humanity shed its hair over time, so to speak, it also slowed its wound healing.

Why humans evolved single-child pregnancies

While birthing twins has been a rare occurrence for humans, research suggests that twins were actually the norm much further back in primate evolution. It’s proposed that single-childbearing turned out to be critical for the evolution of larger babies with larger heads. Discover more about the shift that gives insight into primate evolution.

Were humans the only hominin to walk upright?

When you imagine the line human evolution has taken, you might picture the March of Progress, an image of several chimp-like ancestors marching toward the implied final form: the upright bipedal Homo sapiens. Turns out this image, popularized in the...

Studies estimating the number of years between human generations suggest there have been approximately 10,000 to 12,000 generations of humans.

Research has found that the length of human generations has varied throughout the 300,000 years that Homo sapiens have been around, ranging from about 25 to 30 years. These values come from analyzing genetic mutations, since the blend of them passed onto children changes as parents age.

Some dinosaurs evolved night vision and acute hearing for nocturnal hunting

Paleontologists analyzed the fossilized eye and ear structures of 16 theropods, finding that some had owl-like hearing and huge pupils. These characteristics are consistent with modern-day nocturnal species, including nightjars and geckos.

The evolution of dream science—from interpretation to advanced brain imaging

In the mid-1900s, dream scientists would tape study participants' eyes open, wait for them to fall asleep, and attempt to influence their dreams by shaking, tickling, and more. Now, advanced techniques like MRIs have shed new light on what’s happening in the brain as we sleep.

The body's master clock has 20,000 neurons

The suprachiasmatic nucleus, the master clock in mammals, has 20,000 neurons that help maintain the light-dark cycle in the body. Among its jobs: It receives light input information from the retina and then signals peripheral body clocks to act on this information, driving everything from body temperature to hunger.

About 10%-15% of people experience chronic insomnia

How often would you say you struggle to stay or fall asleep? If it's more than three times per week (and has been going on for at least one month), then you might have one of the most common sleep disorders: insomnia.

Do sleep-tracking apps work?

Can technology help us sleep better? As wearables and apps promise to optimize our nights, this New York Times investigation reveals some troubling findings after columnist Brian Chen used a wearable for two weeks to track his sleep. He discovered that sleep trackers not only provide frequently questionable data but can also paradoxically worsen sleep problems by causing users to obsess over their metrics — a new condition researchers are calling ‘orthosomnia.’

The evolution of the human diet

Could eating like our ancestors make us healthier? One estimate suggests prehistoric hunter-gatherer communities obtained 75% of their calories from meat and fish.

At one point in the 20th century, more than a million Americans had pet monkeys

This choice to domesticate monkeys proved to be trickier than expected, and thus isn't a very appealing option for humans. Monkeys breed more slowly than other animals, while also being susceptible to diseases and challenging to contain.

Why time ticks faster on the moon, which may need its own time zone

Because Earth exerts a stronger gravitational pull than the moon, it lags behind between 56 and 59 microseconds each day, or about one second every 46.5 years. This impacts essential synchronous operations of future electronic equipment on the lunar surface, which could be alleviated by a standardized conversion system between Earth and moon time zones.

Tracking annual working hours per worker in major countries

In 2023, China's workers averaged 2,328 hours per year, far ahead of the second country on the list, the United States, at 1,789. This chart shows the relative decrease of total work time across the world since the late 1800s.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Watch how algorithms can be designed to train themselves and self-improve without human input, to the point where the optimized code is too complex for programmers to understand.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

US housing costs have risen by roughly 175% between 1991 and 2026—but a growing number of Gen Zers are becoming homeowners anyway. In 2025, 4% of homebuyers were Gen Z, up from 3% the year before.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.

The 2026 Ebola outbreak is hampered by a lack of vaccine against the species of the virus, heightening the need for rapid tests to aid in disease control.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.

'Silent' fireworks have gained more interest in recent years as a quieter celebratory option.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

In 1963, a basement renovation in Turkey revealed a passageway to a hidden, multilevel underground city that once housed as many as 20,000 people

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

In 2025, four executives from large tech companies were given positions in the US Army Reserves—including Palantir Chief Technology Officer Shyam Sankar, which reinforced Palantir's ties with the US military and its role as a leading defense partner.

While atoms are normally made of protons, neutrons, and electrons, exotic ones have been built with antimatter—alternate versions of normal matter that live for fractions of a second and are about a billion times as rare.

Many legends about George Washington, including his supposed wooden teeth and the story of cutting down the cherry tree, lack evidence.