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A study published in Nature Communications on 18 August 2026 explained why the narwhal's spirally grooved tusk nevertheless grows almost perfectly straight.
Mineralised collagen fibrils form a left-handed helix in the outer cementum and a right-handed helix in the inner dentine; the opposing twists balance each other and hold the tusk straight.
The narwhal (Monodon monoceros) is a toothed whale of the family Monodontidae, whose only other living member is the beluga whale.
The tusk is an elongated tooth, usually grown by males, reaching about 3 metres and over 10 kg; medieval traders sold them as unicorn horns.
The narwhal is listed as Least Concern on the IUCN Red List and in Appendix II of CITES.
Chirality describes whether a spiral turns to the left or to the right. Bone, dentine and cementum are built from mineralised collagen fibrils that are normally laid down in one consistent direction. In the narwhal tusk the fibrils deviate by small, systematic angles, and they do so in opposite senses in the two tissues - left-handed in the outer cementum, right-handed in the inner dentine. Because the two layers pull against each other, the tusk carries a built-in internal tension that keeps it straight and stiffens it against bending and twisting, even though its surface shows the familiar spiral grooves.
Simple Analogy: A single twisted rope tends to curl on itself. Twist two strands in opposite directions and lay them together and the twists cancel - the rope lies straight and becomes harder to bend. The tusk is built on the same principle, at the scale of nanometres.
India set up its Arctic research station Himadri at Ny-Alesund, Svalbard, on 1 July 2008, became an Observer at the Arctic Council in 2013 (along with China, Japan, South Korea, Singapore and Italy), and released its Arctic Policy, 'India and the Arctic: Building a Partnership for Sustainable Development', on 17 March 2022. India's polar research is run by the National Centre for Polar and Ocean Research (NCPOR), Goa.
The finding came from synchrotron radiation sources, which produce intense X-rays for imaging matter at the nanoscale. India operates two such sources - Indus-1 and Indus-2 - at the Raja Ramanna Centre for Advanced Technology, Indore, under the Department of Atomic Energy.
Structures such as the narwhal tusk, nacre in molluscs and bamboo are studied as models for lightweight, fracture-resistant engineering materials - the application angle exams increasingly prefer for science questions.
GS Paper 3 > Science and Technology - developments and applications; Environment - species and conservation status
General Awareness > Science and Current Affairs
The mineralised tissue covering the outer surface of a tooth root; in the narwhal tusk it carries a left-handed helical collagen arrangement.
The hard tissue forming the bulk of a tooth, lying beneath the enamel or cementum; in the narwhal tusk it carries a right-handed helical arrangement.
The handedness of a structure - whether a spiral turns to the left or the right; mirror images that cannot be superimposed on each other.
A three-dimensional X-ray imaging method that records the direction in which X-rays scatter, not merely how much is absorbed, revealing the orientation of nanoscale fibres inside an intact object.
Species not necessarily facing extinction now, but whose international trade must be controlled so that it stays compatible with their survival.