PARIS, France, Aug 18, 2026 (BSS/AFP) - Narwhals have nature's only 
straight tusk, a single tooth up to three metres long so strange they were 
sold as magical unicorn horns during the Middle Ages.

The tusks have fascinated scientists ever since, but they have proven 
extremely difficult to study because these odd-looking, blubbery whales spend 
most of their lives under the Arctic ice.

But on Tuesday, a large international team of researchers announced they had 
solved a long-running mystery about the tusks: how they get their uniquely 
spiralled yet arrow-straight form.

The left canine tooth of male narwhals grow through their jaw and upper lip, 
jutting out into the animal kingdom's only single tusk. Their right canine 
stays buried in their head.

"Imagine that you had to ride on a bicycle with a broom strapped to your 
head," said Henrik Birkedal, the senior author of a study in Nature 
Communications describing the new discovery.

That is how it must feel for male narwhals to dive deep underwater, the 
chemist at Aarhus University in Denmark told AFP. Yet despite this huge 
"Monty Pythonesque" protuberance, the animals seem to get about just fine, he 
added.

To solve what they called the "narwhal tusk puzzle," the team of biologists, 
chemists and physicists used advanced 3D X-ray technology, including three 
European particle accelerators called synchrotrons.

The tusks are made out of two kinds of dental tissue: dentin on the inside, 
cementum on the outside.

On a molecular level, the inner dentin forms a right-handed spiral while the 
outer cementum forms a left-handed spiral, the powerful X-ray scans revealed.

These two counter-acting forces give the tusks the straight structure that is 
so different to the curved tusks of other animals such as elephants.

"Imagine you turn a screw into a piece of wood, and with each turn, the screw 
penetrates deeper," Birkedal explained. Narwhal tusks are similar -- except 
the screw is pushing further out from the animal's head.

The scientists were also surprised to find growth layers similar to tree 
rings inside the tusks, which offer a glimpse into their lives that can last 
up to 80 years.

To conduct the research, they used tusks from museums as well as those 
collected by Greenland's indigenous Inuit people, who hunt narwhals for food.

- But what are they for? -

This was not the only lingering mystery about narwhal tusks. There has also 
been great debate between scientists about the exact purpose of the world's 
weirdest tooth.

There are several hypotheses, including that the whales use their tusks for 
hunting or to sense temperature and salinity in the water.

But the team behind the new paper believes these options are unlikely because 
tusks are almost exclusively grown by male narwhals -- and females would have 
needed them also for these purposes.

Two males have been observed engaging in what appeared to be a tusk-measuring 
contest in front of a female, suggesting they could be used to establish 
dominance and impress a potential mate.

"This is definitely the most likely purpose of the tusk," study co-author 
Mads-Peter Heide Jorgensen of the Greenland Institute of Natural Resources 
told AFP.

Leading narwhal tusk expert Martin Nweeia, who was not involved in the new 
study, strongly disagreed.

"The primary function of this tusk is as a sensory organ system," the Harvard 
University dental anthropologist told AFP, pointing to his past research.

Despite this disagreement, Nweeia said the study was "one more valuable 
contribution to our knowledge of the tusk micro-anatomy and morphology".