X-rays add new twist to narwhal's spiral tusk

X-rays have revealed surprising new details about narwhal tusks. Research published in Nature Communications reveals that these iconic tusks feature not just one spiral, but an internal second spiral oriented in the opposite direction. The tusk is an enormous canine tooth that grows to one point five to two meters in males, and likely evolved via sexual selection as a social status signal. Yet its true purpose remains debated—females rarely develop them and typically live longer than males, suggesting these elaborate structures are ornamental rather than essential for survival.

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