The unicorn is a legendary creature that has been described since antiquity as a beast with a single large, pointed, spiraling horn projecting from its forehead.
In European literature and art, the unicorn has for the last thousand years or so been depicted as a white horse-like or goat-like animal with a long straight horn with spiralling grooves, cloven hooves, and sometimes a goat's beard. In the Middle Ages and Renaissance, it was commonly described as an extremely wild woodland creature, a symbol of purity and grace, which could be captured only by a virgin. In encyclopedias, its horn was described as having the power to render poisoned water potable and to heal sickness. In medieval and Renaissance times, the tusk of the narwhal was sometimes sold as a unicorn horn.
A bovine type of unicorn is thought by some scholars to have been depicted in seals of the Bronze Age Indus Valley civilization, the interpretation remaining controversial. An equine form of the unicorn was mentioned by the ancient Greeks in accounts of natural history by various writers, including Ctesias, Strabo, Pliny the Younger, Aelian, and Cosmas Indicopleustes. The Bible also describes an animal, the re'em, which some translations render as unicorn.
The unicorn continues to hold a place in popular culture. It is often used as a symbol of fantasy or rarity.
History
Indus Valley civilization
A creature with a single horn, conventionally called a unicorn, is the most common image on the soapstone stamp seals of the Bronze Age Indus Valley civilization ("IVC"), from the centuries around 2000 BC. It has a body more like a cow than a horse, and a curved horn that goes forward, then up at the tip. The mysterious feature depicted coming down from the front of the back is usually shown; it may represent a harness or other covering. Typically the unicorn faces a vertical object with at least two stages; this is variously described as a "ritual offering stand", an incense burner, or a manger. The animal is always in profile on Indus seals, but the theory that it represents animals with two horns, one hiding the other, is disproved by a (much smaller) number of small terracotta unicorns, probably toys, and the profile depictions of bulls, where both horns are clearly shown. It is thought that the unicorn was the symbol of a powerful "clan or merchant community", but may also have had some religious significance.
In South Asia the unicorn is only seen during the IVC period — it disappears in South Asian art ever since. Jonathan Mark Kenoyer stated the IVC "unicorn" has no "direct connection" with later unicorn motifs observed in other parts of world; nonetheless it remains possible that the IVC unicorn had contributed to later myths of fantastical one-horned creatures in West Asia.
Classical antiquity
Unicorns are not found in Greek mythology, but rather in the accounts of natural history, for Greek writers of natural history were convinced of the reality of unicorns, which they believed lived in India, a distant and fabulous realm for them. The earliest description is from Ctesias, who in his book Indika ("On India") described them as wild asses, fleet of foot, having a horn a cubit and a half () in length, and colored white, red and black. Unicorn meat was said to be too bitter to eat.
Ctesias got his information while living in Persia. Unicorns or more likely, winged bulls, appear in reliefs at the ancient Persian capital of Persepolis in Iran. Aristotle must be following Ctesias when he mentions two one-horned animals, the oryx (a kind of antelope) and the so-called "Indian ass" (ἰνδικὸς ὄνος). Antigonus of Carystus also wrote about the one-horned "Indian ass". Strabo says that in the Caucasus there were one-horned horses with stag-like heads. Pliny the Elder mentions the oryx and an Indian ox (perhaps a greater one-horned rhinoceros) as one-horned beasts, as well as "a very fierce animal called the monoceros which has the head of the stag, the feet of the elephant, and the tail of the boar, while the rest of the body is like that of the horse; it makes a deep lowing noise, and has a single black horn, which projects from the middle of its forehead, two cubits [] in length." In On the Nature of Animals (Περὶ Ζῴων Ἰδιότητος, De natura animalium), Aelian, quoting Ctesias, adds that India produces also a one-horned horse (iii. 41; iv. 52), and says (xvi. 20) that the monoceros () was sometimes called cartazonos (), which may be a form of the Arabic karkadann, meaning "rhinoceros".