Somewhere, there is a group of people where a percentage of the population have small "tails". The tail was just an unusually elongated sacrum and coccyx that curved towards the posterior instead of curving inward. It may have been a genetic throwback but I don't believe that they ever concluded definitively. It seems to me that they were all members of a certain caste in India. But I may be wrong on that.
I think the Enquirer had pictures of a newborn, some years ago, with a tail, but then again, they have pictures of people on spaceships too! Merry, Merry Christmas!