A peculiar natural wonder, the narwhal tusk can grow up to three meters in length, emerging as an upper tooth protruding through the whale’s lip on the left side. This tusk, unlike any other mammal’s, grows perfectly straight without any curves.
An international team of researchers has uncovered the reason behind this straight growth pattern, attributing it to the unique structure of opposing spirals present in the tusk. Study author Henrik Birkedal from Aarhus University in Denmark expressed surprise at discovering the two opposing spirals, one turning right and the other left, which contribute to its straight growth.
Newly published research in the journal Nature Communications delves into the intricate details of these opposing spirals and their role in maintaining the tusk’s straight form. The investigation began when Birkedal collaborated with colleagues from organic chemistry, prompted by observations of the consistent leftward spirals in narwhal tusks.
By teaming up with biologists from Greenland and physicists from Sweden, Birkedal’s team employed advanced imaging techniques akin to CT scans to analyze the molecular structure of the tusks and spirals. Their findings unveiled a complex structure with two opposing spirals: a left-handed spiral on the outer layer of cementum and a right-handed one in the inner dentine layer.
This discovery not only solves the mystery of the narwhal’s straight tusk but also offers insights into the structural principles of human bones and similar biological instances. Martin Nweeia, a narwhal biologist at Harvard University, lauded the study’s in-depth analysis of what he deems “the most extraordinary tooth on the planet.”
Nweeia emphasized the tusk’s primary function as a sensory organ, based on his own research, contrary to notions of it being used for defense or feeding. Looking to the future, he hopes for more collaborative research projects with Indigenous communities during the off-season to incorporate traditional knowledge and enhance scientific understanding of narwhals.
