Narwhal Tusks Unveil Twin Spiral Structure Through 3D X-Rays
Researchers using advanced 3D X-ray imaging from multiple synchrotrons revealed that the narwhal’s tusk is a double spiral: the outer cementum twists left, the inner dentin twists right, forming a biological counterbalance that enhances strength. The tusk, which is the narwhal’s left canine and can exceed two meters, grows through the jaw and lip and is commonly seen as a sexual signal, though its exact function remains debated. The findings, published in Nature, also suggest the growth pattern is genetically programmed and that the tusk could serve as a record of environmental change over the animal’s roughly 80-year lifespan, potentially inspiring new materials design.