Narwhal Tusk Reveals Double-Helix Structure

For centuries, narwhal tusks have fueled myth and symbolism, from unicorn horns to coronation chairs, while scientists have long debated their purpose. New multi-scale imaging using tensor tomography reveals that the tusk’s internal structure is a sophisticated double-spiral: an outer left-handed cementum layer and an inner right-handed dentine layer, arranged across scales to create a robust, straight-growing tusk. This opposing helical architecture acts as a biological counterbalance, enabling the tusk to withstand strong hydrodynamic forces as it lengthens beyond two meters. Researchers validated the mechanical advantage by bending tests and explained how the ‘double-spiral’ architecture reinforces the tooth much like concrete reinforcement fibers. Despite progress in understanding the structure, the exact biological function of the tusk remains debated, with theories ranging from signaling to hunting or play, alongside its enduring cultural mystique. The findings illustrate how ancient folklore and modern imaging can converge to illuminate one of the ocean’s most enduring mysteries.