Narwhal tusk structure explained by researchers

An international research team, led by professors from Aarhus University, has identified the biological mechanism behind the unique structure of the narwhal tusk. Using advanced 3D X-ray imaging to examine specimens from Greenland, scientists discovered that the tusk consists of two distinct layers of dental tissue that form spiral patterns in opposite directions.

The study, published in Nature/Nature Communications, reveals that while the outer cementum twists in one direction, the inner dentine twists in the other. This opposing spiral structure creates internal tension that allows the tusk to grow straight and maintain significant strength and flexibility without bending or breaking under Arctic conditions.

While the exact evolutionary purpose of the tusk remains a subject of debate—with theories ranging from sexual selection to sensory detection of water changes—the structure serves as a biological record of Arctic environmental conditions over the animal's lifetime.