Maria Chikina, University of Pittsburgh

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com.

Why don’t humans have hair all over their bodies like other animals? – Murilo, age 5, Brazil

Have you ever wondered why you don’t have thick hair covering your whole body like a dog, cat or gorilla does?

Humans aren’t the only mammals with sparse hair. Elephants, rhinos and naked mole rats also have very little hair. It’s true for some marine mammals, such as whales and dolphins, too.

Scientists think the earliest mammals, which lived at the time of the dinosaurs, were quite hairy. But over hundreds of millions of years, a small handful of mammals, including humans, evolved to have less hair. What’s the advantage of not growing your own fur coat?

I’m a biologist who studies the genes that control hairiness in mammals. Why humans and a small number of other mammals are relatively hairless is an interesting question. It all comes down to whether certain genes are turned on or off.

Hair benefits

Hair and fur have many important jobs. They keep animals warm, protect their skin from the sun and injuries and help them blend into their surroundings.

They even assist animals in sensing their environment. Ever felt a tickle when something almost touches you? That’s your hair helping you detect things nearby.

Humans do have hair all over their bodies, but it is generally sparser and finer than that of our hairier relatives. A notable exception is the hair on our heads, which likely serves to protect the scalp from the sun. In human adults, the thicker hair that develops under the arms and between the legs likely reduces skin friction and aids in cooling by dispersing sweat.

So hair can be pretty beneficial. There must have been a strong evolutionary reason for people to lose so much of it.

Why humans lost their hair

The story begins about 7 million years ago, when humans and chimpanzees took different evolutionary paths. Although scientists can’t be sure why humans became less hairy, we have some strong theories that involve sweat.

Humans have far more sweat glands than chimps and other mammals do. Sweating keeps you cool. As sweat evaporates from your skin, heat energy is carried away from your body. This cooling system was likely crucial for early human ancestors, who lived in the hot African savanna.

Of course, there are plenty of mammals living in hot climates right now that are covered with fur. Early humans were able to hunt those kinds of animals by tiring them out over long chases in the heat – a strategy known as persistence hunting.

Humans didn’t need to be faster than the animals they hunted. They just needed to keep going until their prey got too hot and tired to flee. Being able to sweat a lot, without a thick coat of hair, made this endurance possible.

Genes that control hairiness

To better understand hairiness in mammals, my research team compared the genetic information of 62 different mammals, from humans to armadillos to dogs and squirrels. By lining up the DNA of all these different species, we were able to zero in on the genes linked to keeping or losing body hair.

Among the many discoveries we made, we learned humans still carry all the genes needed for a full coat of hair – they are just muted or switched off.

In the story of “Beauty and the Beast,” the Beast is covered in thick fur, which might seem like pure fantasy. But in real life some rare conditions can cause people to grow a lot of hair all over their bodies. This condition, called hypertrichosis, is very unusual and has been called “werewolf syndrome” because of how people who have it look.

In the 1500s, a Spanish man named Petrus Gonsalvus was born with hypertrichosis. As a child he was sent in an iron cage like an animal to Henry II of France as a gift. It wasn’t long before the king realized Petrus was like any other person and could be educated. In time, he married a lady, forming the inspiration for the “Beauty and the Beast” story.

While you will probably never meet someone with this rare trait, it shows how genes can lead to unique and surprising changes in hair growth.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Maria Chikina, Assistant Professor of Computational and Systems Biology, University of Pittsburgh

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Daniel Apai, University of Arizona

A team of astronomers announced on April 16, 2025, that in the process of studying a planet around another star, they had found evidence for an unexpected atmospheric gas. On Earth, that gas – called dimethyl sulfide – is mostly produced by living organisms.

In April 2024, the James Webb Space Telescope stared at the host star of the planet K2-18b for nearly six hours. During that time, the orbiting planet passed in front of the star. Starlight filtered through its atmosphere, carrying the fingerprints of atmospheric molecules to the telescope.

By comparing those fingerprints to 20 different molecules that they would potentially expect to observe in the atmosphere, the astronomers concluded that the most probable match was a gas that, on Earth, is a good indicator of life.

I am an astronomer and astrobiologist who studies planets around other stars and their atmospheres. In my work, I try to understand which nearby planets may be suitable for life.

K2-18b, a mysterious world

To understand what this discovery means, let’s start with the bizarre world it was found in. The planet’s name is K2-18b, meaning it is the first planet in the 18th planetary system found by the extended NASA Kepler mission, K2. Astronomers assign the “b” label to the first planet in the system, not “a,” to avoid possible confusion with the star.

K2-18b is a little over 120 light-years from Earth – on a galactic scale, this world is practically in our backyard.

Although astronomers know very little about K2-18b, we do know that it is very unlike Earth. To start, it is about eight times more massive than Earth, and it has a volume that’s about 18 times larger. This means that it’s only about half as dense as Earth. In other words, it must have a lot of water, which isn’t very dense, or a very big atmosphere, which is even less dense.

Astronomers think that this world could either be a smaller version of our solar system’s ice giant Neptune, called a mini-Neptune, or perhaps a rocky planet with no water but a massive hydrogen atmosphere, called a gas dwarf.

Another option, as University of Cambridge astronomer Nikku Madhusudhan recently proposed, is that the planet is a “hycean world”.

That term means hydrogen-over-ocean, since astronomers predict that hycean worlds are planets with global oceans many times deeper than Earth’s oceans, and without any continents. These oceans are covered by massive hydrogen atmospheres that are thousands of miles high.

Astronomers do not know yet for certain that hycean worlds exist, but models for what those would look like match the limited data JWST and other telescopes have collected on K2-18b.

This is where the story becomes exciting. Mini-Neptunes and gas dwarfs are unlikely to be hospitable for life, because they probably don’t have liquid water, and their interior surfaces have enormous pressures. But a hycean planet would have a large and likely temperate ocean. So could the oceans of hycean worlds be habitable – or even inhabited?

Detecting DMS

In 2023, Madhusudhan and his colleagues used the James Webb Space Telescope’s short-wavelength infrared camera to inspect starlight that filtered through K2-18b’s atmosphere for the first time.

They found evidence for the presence of two simple carbon-bearing molecules – carbon monoxide and methane – and showed that the planet’s upper atmosphere lacked water vapor. This atmospheric composition supported, but did not prove, the idea that K2-18b could be a hycean world. In a hycean world, water would be trapped in the deeper and warmer atmosphere, closer to the oceans than the upper atmosphere probed by JWST observations.

Intriguingly, the data also showed an additional, very weak signal. The team found that this weak signal matched a gas called dimethyl sulfide, or DMS. On Earth, DMS is produced in large quantities by marine algae. It has very few, if any, nonbiological sources.

This signal made the initial detection exciting: on a planet that may have a massive ocean, there is likely a gas that is, on Earth, emitted by biological organisms.

Scientists had a mixed response to this initial announcement. While the findings were exciting, some astronomers pointed out that the DMS signal seen was weak and that the hycean nature of K2-18b is very uncertain.

To address these concerns, Mashusudhan’s team turned JWST back to K2-18b a year later. This time, they used another camera on JWST that looks for another range of wavelengths of light. The new results – announced on April 16, 2025 – supported their initial findings.

These new data show a stronger – but still relatively weak – signal that the team attributes to DMS or a very similar molecule. The fact that the DMS signal showed up on another camera during another set of observations made the interpretation of DMS in the atmosphere stronger.

Madhusudhan’s team also presented a very detailed analysis of the uncertainties in the data and interpretation. In real-life measurements, there are always some uncertainties. They found that these uncertainties are unlikely to account for the signal in the data, further supporting the DMS interpretation. As an astronomer, I find that analysis exciting.

Is life out there?

Does this mean that scientists have found life on another world? Perhaps – but we still cannot be sure.

First, does K2-18b really have an ocean deep beneath its thick atmosphere? Astronomers should test this.

Second, is the signal seen in two cameras two years apart really from dimethyl sulfide? Scientists will need more sensitive measurements and more observations of the planet’s atmosphere to be sure.

Third, if it is indeed DMS, does this mean that there is life? This may be the most difficult question to answer. Life itself is not detectable with existing technology. Astronomers will need to evaluate and exclude all other potential options to build their confidence in this possibility.

The new measurements may lead researchers toward a historic discovery. However, important uncertainties remain. Astrobiologists will need a much deeper understanding of K2-18b and similar worlds before they can be confident in the presence of DMS and its interpretation as a signature of life.

Scientists around the world are already scrutinizing the published study and will work on new tests of the findings, since independent verification is at the heart of science.

Moving forward, K2-18b is going to be an important target for JWST, the world’s most sensitive telescope. JWST may soon observe other potential hycean worlds to see if the signal appears in the atmospheres of those planets, too.

With more data, these tentative conclusions may not stand the test of time. But for now, just the prospect that astronomers may have detected gasses emitted by an alien ecosystem that bubbled up in a dark, blue-hued alien ocean is an incredibly fascinating possibility.

Regardless of the true nature of K2-18b, the new results show how using the JWST to survey other worlds for clues of alien life will guarantee that the next years will be thrilling for astrobiologists.

Daniel Apai, Associate Dean for Research and Professor of Astronomy and Planetary Sciences, University of Arizona

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Christina Erickson, University of North Dakota

Nearly a half-century after the Supreme Court ruled that school spankings are permissible and not “cruel and unusual punishment”, many U.S. states allow physical punishment for students who have misbehaved.

Today, over a third of the states allow teachers to paddle or spank students. More than 100,000 students are paddled in U.S. schools each year.

Christina Erickson, an associate dean and professor of social work at the University of North Dakota, wrote a book on the subject: “Spanked: How Hitting Our Children is Harming Ourselves.” She discussed the scope of the practice and its effects with The Conversation.

What spanking legislation exists worldwide?

Around the world, 68 countries have banned the hitting of children in any form, including spanking. This movement began in 1979 with Sweden’s ban on all forms of physical punishment, including spanking in any setting, and including in the family home.

The pace of change quickened in the early 2000s when more countries adopted similar laws. For example, the legal language of countries like Nepal rests on an emerging definition of children as rights holders similar to adults and as humans worth protecting from harm.

What are US policies toward spanking?

Each state in the U.S. has its own child abuse laws, and all states, tribes and territories aim to protect children from abuse. But all state laws also allow parents to hit their children if it does not leave an injury or a mark.

A typical example is Oklahoma’s definition of child abuse and neglect. It includes an exception that permits parents to use ordinary force as a means of discipline, including spanking, using an implement like a switch or a paddle. However, leaving evidence of hitting, such as welts, bruises, swelling or lacerations, is illegal and considered child abuse in all states.

Parental spanking of children is considered unique from other physical violence because of the relational context and the purpose. Laws entitle parents to hit their children for the purpose of teaching a lesson or punishing them to improve behavior. Children are the only individuals in society who can be hit by another person and the law does not regard it as assault.

Spanking’s impact on a child is unfortunately similar to abusive hitting. Spanking has been labeled as an “Adverse Childhood Experience,” or ACE. These are events that cause poor health outcomes over the span of one’s life.

The practice of spanking also affects parents. Acceptance of the physical discipline of spanking puts parents at risk for the escalation of physical punishment that leads to abuse.

Parents who spank their child have the potential to abuse them and be caught in a legal and child protection system that aims to protect children from harm. It is unclear what triggers a parent to cross over from discipline into abuse. Research shows that spanking at a young age, such as a 1-year-old, increases the chance of involvement by Child Protective Services by 33%.

Some school districts require permission from parents to allow disciplinary paddling in school, while others do not require any communication. State law does not assure agreement between parents and school districts on what offenses warrant a paddling. Parents may feel they have no alternative but to keep their child in school, or fear reprisal from school administrators. Some students are old enough to denounce the punishment themselves.

Is spanking considered the same as hitting?

The term spank conceals the concept of hitting and is so commonplace it goes unquestioned, despite the fact that it is a grown adult hitting a person much smaller than them. The concept is further concealed because hitting a child’s bottom hides any injuries that may occur.

Types of hitting that are categorized as spanking have narrowed over the years but still persist. Some parents still use implements such as tree switches, wooden spoons, shoes or paddles to “spank” children, raising the chances for abuse.

Most spanking ends by the age of 12, partly because children this age are able to fight back. When a child turns 18, parental hitting becomes the same as hitting any other adult, a form of domestic violence or assault throughout the U.S.

There is a lack of a consistent understanding of what constitutes a spanking. The definition of spanking is unique to each family. The number of hits, clothed or not, or using an implement, all reflect geographical or familial differences in understanding what a spanking is.

How do US adults view spanking?

People in the United States generally accept spanking as part of raising children: 56% of U.S. adults strongly agree or agree that “… it is sometimes necessary to discipline a child with a good, hard spanking.” This view has been slowly changing since 1986, when 83% of adults agreed with that statement.

The laws worldwide that protect children from being hit usually begin by disallowing nonparental adults to hit children. This is happening in the U.S. too, where 31 states have banned paddling in schools.

At a national level, efforts have been made to end physical punishment in schools. However, 19 states still allow spanking of children in public schools, which was upheld by a 1977 Supreme Court case.

With the slow but steady drop of parents who believe that sometimes children need a good hard spanking, as well as the ban of paddling in schools in 31 states, one could argue that the U.S. is moving toward a reduction in spanking.

What does research say about spanking?

Spanking’s negative influence on children’s behavior has been documented for decades. Spanking seems to work in the moment when it comes to changing or stopping the immediate behavior, but the negative effects are hidden in the short term and occur later in the child’s life. Yet because the spanking seemed to work at the time, the parent doesn’t connect the continued bad behavior of the child to the spanking.

An abundance of research shows that spanking causes increased negative behaviors in childhood. Spanking lowers executive functioning for children, increases dating violence as teenagers and even increases struggles with mental health and substance abuse in adulthood. Spanking does not teach new or healthy behaviors, and is a stress-inducing event for the child and the adult hitting them.

No studies have shown positive long-term benefits from spanking. Because of the long-standing and expansive research findings showing a range of harm from spanking and the increased association with child abuse, the American Psychological Association recommends that parents should never spank their children.

What are some resources for parents?

Consider these questions when choosing a discipline method for your child:

• Is the expectation of your child developmentally accurate? One of the most common reasons parents spank is because they are expecting a behavior the child is not developmentally able to execute.

• Can the discipline you choose grow with your child? Nearly all spanking ends by age 12, when kids are big enough to fight back. Choose discipline methods you can use over the long term, such as additional chores, apologies, difficult conversations and others that can grow with your child.

• Might there be another explanation for your child’s behavior? Difficulty of understanding, fear or miscommunication? Think of your child as a learner and use a growth mindset to help your child learn from their life experiences.

Parents are the leaders of their families. Good leaders show strength in nonthreatening ways, listen to others and explain their decisions. Don’t spoil your kids. But being firm does not have to include hitting.

Is spanking children good for parents?

Doubtful. Parents who hit their kids may be unaware that it influences their frustration in other relationships. Expressing aggression recharges an angry and short-tempered internal battery that transfers into other parts of the adults’ lives.

Practicing calm when with your children will help you be calmer at work and in your other relationships. Listening to and speaking with a child about challenges, even from a very early age, is the best way to make it part of your relationship for the rest of your life.

Choose a method that allows you to grow. Parents matter too.

Christina Erickson, Associate Dean in the College of Nursing and Professional Disciplines, University of North Dakota

This article is republished from The Conversation under a Creative Commons license. Read the original article.