The Narwhal Tusk: History, Function, and Evolution

Key Insight

The narwhal's tusk, historically, was confused with the mythical unicorn's horn, with its existence reported as early as the fifth century B.C. by Greek physician Ctesias and later supported by Aristotle and Pliny. This legend gained 'unwitting and ironic' authority from biblical translations. During the Renaissance, actual narwhal tusks provided 'irrefutable' concrete evidence for the unicorn's existence, making the horn a highly prized and practical item. European royalty in the 14th and 15th centuries, wary of poisonings, sought the unicorn's horn as the greatest proof against such attacks, valuing it as an amulet, talisman, weapon, and medicine chest, capable of preserving against various ills.

In the Middle Ages, the narwhal's tusk, traded in pieces as unicorn horn, sold for immense fortunes, reportedly twenty times its weight in gold. By the mid-16th century, fewer than fifty whole tusks were recorded in Europe, often becoming gifts to royalty or the church and sought after as booty. The trade relied on Greenlandic and Icelandic sources, with sailors unknowingly providing immense value to European buyers who often had no concept of the narwhal itself. The cartographer Gerhard Mercator in 1621 and Danish professor Ole Wurm in 1638 were among the first to correctly identify the narwhal as the tusk's origin, but the unicorn legend was too deeply ingrained in European society and the tusk too valuable to be easily dismissed.

Scientifically, the tusk is a continually growing, fully vascularized tooth, typically developing from the left side of the male's upper jaw, spiraling right to left; rarely, females or both sexes can develop two. Early theories about its purpose—as a rake, spear, or defensive weapon—were largely unsupported due to the existence of tuskless narwhals and the tusk's brittleness. The primary, and perhaps sole, function is now considered social, with males engaging in displays, crossing tusks like swords, or pressing them against others' backs. Such interactions frequently result in scarred heads and broken tusk tips, found in 20 to 30 percent of narwhals. D'Arcy Wentworth Thompson's theory, positing that the tusk's characteristic twist is a result of slight torque from the narwhal's tail resisting in its socket, has remained unchallenged since 1942. For Eskimos, the tusk historically served utilitarian purposes as a strong, straight timber substitute for spear shafts, tent poles, or sledge parts in treeless regions.