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. S ome 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. T he 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.
T here 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.