Danish researchers led from Aarhus University say they have found a likely explanation for why the narwhal’s tusk grows straight while also twisting into a spiral. The findings were reported in Denmark on August 19, 2026.
An international research team led from Aarhus University spent six years studying a narwhal tusk from Greenland, DR reports. Using advanced 3D X-ray methods, the researchers examined the tusk down to its molecular building blocks.
According to DR, the results point to the tusk’s internal structure as the reason it grows straight and rotates at the same time. Henrik Birkedal, professor at the Department of Chemistry at Aarhus University, told P1 Morgen that the team set out to understand the screw-shaped spiral structure.
The researchers found that the tusk consists of different layers, with collagen fibers oriented in specific directions. Together, those layers form a spiral pattern. Per Birkedal, combining several experiments allowed the team to link fibril orientation to the overall spiral.
Phys.org reports that the tusk contains not one spiral but two opposing spirals, with the outside twisting left and the inside twisting right. The same outlet notes that the opposing spirals make the tusk more stable against bending and twisting, and that the pattern is preserved across annual growth layers.
France 24 adds a tissue distinction, with dentine on the inside and cementum on the outside, twisting in opposite directions. As reported by CBC, the team believes it has explained why the tusk grows so straight.
Why the narwhal has the tusk is still unresolved
DR notes that the researchers now know more about how the tusk grows, but not why the animal has it. The most widespread theory is that it serves a social function. Birkedal says the best current hypothesis involves display toward females and signaling status, while theories about a role in hunting also exist.
The measurements required travel to international research facilities, where teams typically get only a few days on the advanced equipment. According to Birkedal, that can mean working around the clock. The project was also delayed by the coronavirus pandemic.
The European Synchrotron Radiation Facility states that an international team led by Aarhus University solved how the tusk acquires its structure, confirming the synchrotron-based part of the work. Aarhus University’s Institute of Chemistry describes the project as an effort to determine how molecular building blocks create the helix.
Phys.org and CBC both tie the news to a fresh publication in the journal Nature Communications on August 18, 2026. DR frames the result as a possible explanation, while the two international outlets describe the mystery as solved.
The tusk also contains structures resembling annual rings. According to DR, the researchers hope to use them to read details about the animal’s life, including how quickly it grew.
