How does the "spin" on your head turn? It turns out to be related to the northern and southern hemispheres! ?

Looking at a newborn baby is an exciting moment for parents - a huge surge of love, a strong desire to protect for the first time, and an anxious sense of responsibility. They are in awe and wonder at the tiny hands, feet and ears. A baby's hair swirls clockwise or counterclockwise from the scalp.

Of course, maybe that last point doesn’t bother parents. But for Marjolaine Willems, a clinical geneticist at the University Hospital of Montpellier in France, it was a different story. When her identical twin daughters were born, she noticed that their hair whorls went in the same direction—clockwise—but one was on the right side of the top of her head, and the other on the left. They weren’t exactly alike. A few years later, Willems’ sister gave birth to twins—whorls were in the same exact position. As a clinical geneticist, Willems couldn’t get over the discovery.

Now, after 13 years of observing the heads of twins and singleton babies, her team has published a paper on the link between hemisphere orientation and hair whorl formation[1], for which they have won the 2024 Ig Nobel Prize in Anatomy[2]. The Ig Nobel Prizes honour scientific research that is both hilarious and thought-provoking. Studying whether people in the southern hemisphere are more likely to have counter-clockwise hair whorls than those in the northern hemisphere is a bit funny, but it also shows how diverse humans are – from tiny changes in our genes to the visible traces of those changes in our appearance.

© Better Not Younger

As long as there's hair on your head, there's at least one hair whorl - a small patch of hair that grows out of the scalp in a spiral. This makes sense, Williams explains. It's impossible to spread your hair flat on a sphere, so there's always going to be a whorl somewhere.

© Wikipedia

Obviously, the human head isn't truly spherical, but it is certainly rounded at the top, so we all have whorls. Most people - 98.5% - only have one whorl, while the lucky 1.5% have two (or maybe not so lucky for your barber). Whorls can be in the center, on the right, or on the left side of the head, and can rotate clockwise or counterclockwise. You can try to find your whorl by feeling it with your hands, or it may be easier to have a friend help you.

So what makes our hair grow the way it does? "We don't know how it starts," Williams says. Scientists do know that it probably has some genetic basis; other hairy mammals display similar whorls in rounded areas of their hair, such as the forehead of a cow, or the head, legs or rump of a dog or horse. People with rare genetic conditions may be more prone to double whorls, or to whorls that grow on the forehead rather than the top of the head.

© Pinterest

To investigate whether whorls are caused by genetics or the environment, Williams and her colleagues decided to study identical twins and compare them with non-twin populations from the Northern and Southern hemispheres. Twin studies can help identify the influence of genetic factors, while differences between the hemispheres could indicate that the environment plays a role in the direction of whorls.

Williams first asked the parents for permission to look at the top of their newborns' heads. "The first thing a gynecologist will ask parents is if they would like to participate in a special study," she said. When parents are told that the study is about how hair grows and forms whorls, most of them laugh. Babies are her first choice because they don't have much hair, making it easier to see whorls. For children or adults with longer hair, it's more difficult to identify whorls.

© ResearchGate

The scientists compared 37 pairs of French twins, 50 singleton children from France in the northern hemisphere, and 50 singleton children from Chile in the southern hemisphere (they didn't look at the Chilean twins, and unfortunately I can't tell why). Most of the whorls were clockwise. Among the twins, 70% had the same direction of hair whorls—86% of the twins had clockwise hair whorls. Among the non-twin children in France, only about 4% had counterclockwise hair whorls. But in Chile, 28% had counterclockwise hair whorls. The scientists concluded that genetics definitely played a role, but that environmental factors might also play a role.

Williams and her colleagues joked that the hair whorls might be related to the Coriolis Effect, a deflection pattern that affects large, unattached objects on Earth. Because Earth is roughly spherical, the equator spins faster than the poles. Objects moving long distances from the equator to the North and South Poles will deflect because the poles move more slowly. In the Northern Hemisphere, objects deflect to the right. In the Southern Hemisphere, they deflect to the left.

In the Northern Hemisphere, hurricanes rotate counterclockwise (left, Hurricane Daniel in 2006) because the air is deflected to the right by the Coriolis effect as it flows toward the center. In the Southern Hemisphere, hurricanes rotate clockwise (right, Cyclone Iasi in 2011) because the Coriolis deflection is to the left. © Roger Williams University Open Publishing

The Coriolis effect explains why hurricanes and cyclones spin in opposite directions in the Northern and Southern Hemispheres. Within the broad expanse of these massive storms, the Coriolis effect causes wind and rain to swirl counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere—and they can be just as destructive to humans. The Coriolis effect is also the origin of that old Australian toilet water myth.

However, in a toilet, the volume and distance of water flow are too small to be affected by the Coriolis effect - which may be a comfort to people flushing toilets at the equator.

© Shutterstock

If toilets aren’t affected by the Coriolis effect, then neither should hair, Williams says. “It was a hypothetical joke,” she points out. Williams and her colleagues did try to take their paper seriously, “but when all the colleagues were laughing, we knew it was pretty funny.” However, the prospect of genes and environment working together raises more scientific questions. This means that a deeper look at how hair forms whorls on the head could help people understand how we develop—how ​​genes and environment work together to shape the reality of our faces and heads. It’s a tiny difference, but it can provide a lot of clues to how cells divide, form and migrate, and what to do when the process goes wrong. The whorl itself is full of wonder, just like tiny hands and feet and tiny noses. It’s a sign that cells divide, migrate, organize and create wonderful new things.

References:

[1]www.sciencedirect.com/science/article/abs/pii/S2468785523002859[2]improbable.com/ig/winners/#ig2024

By Bethany Brookshire

Translated by tim

Proofreading/tamiya2

Original article/www.scientificamerican.com/article/does-the-coriolis-effect-cause-your-cowlick/

This article is based on the Creative Commons License (BY-NC) and is published by tim on Leviathan

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