A 2024 study tried to find out if hair swirls turn differently in the Northern and Southern hemispheres; after studying 174 children and twins, researchers found more counterclockwise whorls in the South and a genetic link

Look at the crown of your head, and you will probably find a small spiral where your hair seems to grow in a particular direction. For most people, it is easy to ignore. But what if the direction of that tiny swirl is influenced by where you were born?

That was the surprisingly specific question researchers from France and Chile investigated in a study of human hair whorls. They wanted to know whether the hair on people's heads in the Northern Hemisphere tends to swirl in the same direction as in the Southern Hemisphere, or whether the two populations show different patterns.

The research eventually became the subject of an Ig Nobel Prize. The 2024 Anatomy Prize was awarded to Marjolaine Willems and colleagues for studying whether the hair on the heads of most people in the northern hemisphere swirls in the same direction (clockwise or counter-clockwise?) as hair on the heads of most people in the southern hemisphere.


The question sounds humorous. The science behind it, however, touches on genetics, development and the way cells organize themselves before birth.

The hair-whorl question that crossed hemispheres

A hair whorl, often called a cowlick, is the spiral pattern formed by hair on the scalp. Most people have one, although some have multiple whorls. They can rotate clockwise or counterclockwise and can appear in different positions on the scalp.

Scientists have long known that these patterns are established during prenatal development. What has remained less clear is exactly what determines their position and direction.

The researchers behind the study, published in the Journal of Stomatology, Oral and Maxillofacial Surgery in April 2024, examined whether genetics could explain similarities between twins and whether environmental or geographic factors could influence the direction of hair whorls.

Their study included 74 twins (37 pairs), along with 50 children from the Northern Hemisphere and 50 from the Southern Hemisphere.

The Northern Hemisphere group consisted of children born in Paris, France, while the Southern Hemisphere group consisted of children born in Santiago, Chile.

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Did Northern and Southern Hemisphere hair swirl differently?

The researchers found a striking difference. Their results indicated that counterclockwise whorls were more frequent in the Southern Hemisphere than in the Northern Hemisphere. The difference was statistically significant, with the study reporting p < 0.001.

The odds ratio for the Northern Hemisphere was 0.04 [0.03; 0.05], compared with 0.28 [0.24; 0.32] for the Southern Hemisphere.

The researchers also found evidence that twins were more likely to have hair whorls rotating in the same direction.

The odds ratio for opposite rotation directions between twins was ≠1 (p = 0.017), suggesting that whorls tended to rotate in the same direction within twin pairs.

Together, the findings pointed toward a combination of genetic and environmental influences.

The researchers concluded: “We suggest that hair whorl formation is a genetically determined developmental process that can be influenced by extrinsic environmental factors.”

They also stressed that larger studies would be needed to confirm the unexpected geographic difference.

Why would geography affect a hair whorl?

This is where the study becomes more complicated than the joke surrounding it. The researchers were not claiming that simply living in the Northern or Southern Hemisphere makes someone's hair turn clockwise or counterclockwise.

Their results showed an association between the populations studied and whorl direction. But population-specific genetic differences could not be completely ruled out.

The study itself acknowledged this limitation, noting that “genetic effects resulting from specific population characteristics could not be formally ruled out.”

That distinction matters. The researchers were interested in hair whorls as a model for understanding development. The scalp is not simply a flat surface on which hairs happen to grow. Hair follicles develop through highly organized biological processes before birth.

The study suggests that examining seemingly trivial patterns, such as hair whorls, could offer clues about how cells are arranged in three-dimensional structures during development.

What twins revealed about the mystery

Twins provided another important part of the investigation. The researchers compared twins from different types of pregnancies to explore whether genetics played a role in determining whorl rotation.

Their findings showed that twin pairs preferentially had whorls rotating in the same direction.

However, they did not find a significant association for whether the whorl was located on the same or opposite side of the scalp. The odds ratio for different whorl laterality was not significant (p = 0.869).

This helped strengthen the researchers' argument that genetics could contribute to the whorl's direction without necessarily determining every aspect of its position.

The researchers described their findings as evidence that whorl characteristics were “partially determined by genetic factors.”

The strange science behind a seemingly ordinary cowlick

Hair whorls have attracted scientific attention before. Previous research has examined whether they might be associated with characteristics ranging from handedness to behavior.

But the study's authors pointed out that several of those claims had been invalidated. The researchers instead focused on hair whorls as a developmental phenomenon.

They even connected the subject to a mathematical idea known as the hedgehog theorem of algebraic topology. In simple terms, the theorem describes why a continuous hairy surface, such as a sphere, cannot have all its hairs lying smoothly in one direction without producing a point where the hairs form a whorl.

Humans, of course, do not have completely spherical heads. Yet the basic geometry helps explain why whorl-like patterns naturally emerge on hairy surfaces.

So, does your hemisphere determine your hair swirl?

Not necessarily. The study found that counterclockwise whorls were more frequent among the Southern Hemisphere population studied, while twins tended to have whorls that rotated in the same direction.

But the researchers did not establish that the hemisphere in which a person is born directly determines the direction of their hair whorl.

Their findings instead suggest that genetic factors and environmental influences may both contribute to how these tiny spirals form. And that is what makes the research more interesting than the question initially suggests.