Evolution and Nature of Unicorns
Despite popular belief, Unicorns did not evolve from horse-like ancestors. Instead they are descendants of cloven-hoofed mammals like pigs, camels deer, and antelope. This is because unicorns have cloven hooves and have true horns which you will find on no horse, only cloven-hoofed animals. To narrow down their "relatives" even more, we can say that they are more likely to be related to antelope as opposed to deer because of the horn. Deer antlers are bonelike structures that grow out of the males (generally) forehead in the spring and summer. The antlers are then shed for the winter months. Now the horns found in antelope, cattle and seep are never shed and continue to grow throughout the animal’s lifetime. Also, both sexes typically grow horns where as only the buck (male deer) grows antlers. The earliest known cloven-hoofed mammal fossils date from the Eocene times which was about 50 million years ago. The stock that gave rise to the antelope. Their kin did not, however, appear until the Miocene Era, which was when many kinds of antelope-like creatures first started appearing in southern Europe and the Great Plains of Asia. One of these mammals was the Prostrepsceros in India, which is probably an ancestor to both the antelope and unicorn.
Some of the fossil types found in the cooler forests of Asia revealed the Plioceros bicornus which probably moved into the Alps of Europe and some into the southern slopes of the Himalayas and was also most likely the earliest type of unicorn. Since the population of the oldest known unicorn was split (some in Himalayas, some in Europe) they adapted to their environment and grew apart in similarities, thus making the European Unicorns and the Asian Unicorns.
The classical unicorn Equus Monoceros, is perhaps the most common, according to cryptozoologists. There is also the Equus assinoceros, which is thought to have existed in India and resemble an ass.
There are a few explanations for the lack of unicorns in modern day. The most famous perhaps, is the story of Noah and the flood. Noah, who was gathering a male and female of each species, failed to take a pair of unicorns onto his ark. When the flood occurred, the unicorns were wiped out. Another belief is that they were hunted to extinctions, much like the do-do bird. There is yet another is the belief. After the demand for the unicorn horn decreased (perhaps because of a lack of belief in unicorns altogether), they simply faded out. Moving away from the human world.
A unicorn has magical powers, rooted in the horn. Their horns, which are spiraled (tightly or loosely), can be white, gold, black, or even rainbow colored, depending on the age of the unicorn. It is even theorized that the horns are whitish on the outside but black on the inside. Both males and females grow horns, but predictably, the female horns are smaller. Males horns continue to grow throughout their lives. The youth have white horns. They are believed to have medicinal uses and made of an unusually strong substance. It is believed to be an anti-toxin, and able to purify entire rivers with a single touch of the horn in the water. Males are thought to be extremely territorial during the mating season. They will attack other males presumable to keep them away from potential mates. Female unicorns are the most attracted to the male with the largest horn. They are believed to be sexually active in the fall, and have young in the spring (usually only one offspring). Gestation is roughly the same time for unicorns that is is for humans - 9 months. The female then leaves the males territory and secludes herself in the forest for the winter.
They are also said to be attracted to virgins, which is one way that they were hunted. Virgins represent purity, and a unicorn is very pure. By using a virgin, hunters were able to seek out unicorns and take their horns, killing them. Unicorns are also able to detect virgins. If the horn of a unicorn pierces the heart of the woman, she is not a virgin. If it passes through her, the maiden is pure (virgin). This method is sometimes said to be applied to trustworthy and sincere people in general, such as in the Xanth books by Piers Anthony