A unique feature of the natural world, the narwhal tusk, which can grow up to three meters long, is an upper tooth that protrudes through the whale’s lip on the left side. Unlike other mammal tusks, the narwhal tusk grows perfectly straight without any curves.
A team of international researchers has uncovered the reason behind the tusk’s straight growth, attributing it to the distinct pattern of opposing spirals it possesses. In a study led by Henrik Birkedal from Aarhus University in Denmark, the team found two opposing spirals — one spiraling to the right and the other to the left — which contribute to the straight growth of the tusk.
The research, recently published in the journal Nature Communications, originated from Birkedal’s collaboration with a colleague specializing in organic chemistry. Intrigued by the consistent leftward spiral of narwhal tusks observed in Greenland, the team embarked on a comprehensive investigation into the molecular structure of these unique tusks.
Through advanced imaging techniques akin to CT scans, the researchers discovered that the tusks, primarily found in male narwhals, are composed of dentine and cementum, lacking the enamel layer present in human teeth. The imaging revealed the presence of two opposing spirals — a left-handed spiral on the outer cementum layer and a right-handed spiral in the inner dentine layer.
This groundbreaking discovery not only solves the mystery of the narwhal’s straight tusk but also presents potential insights into the structural principles of human bones and other similar biological instances, according to Birkedal.
Renowned narwhal biologist Martin Nweeia from Harvard University hailed the research for delving into what he describes as the “most extraordinary tooth on the planet.” While emphasizing the multifunctional nature of teeth, Nweeia’s own research has highlighted the tusk’s primary role as a sensory organ rather than for defense or feeding purposes.
Looking ahead, Nweeia advocates for more off-season studies and collaborative efforts with Indigenous communities in researching narwhals, emphasizing the invaluable insights provided by traditional knowledge alongside scientific inquiry. He underscores the importance of interdisciplinary collaboration, as exemplified by Birkedal’s recent study, which harnessed expertise from Greenland and Sweden to achieve groundbreaking results.
