Human embryos have a tail that measures about one-sixth of the size of the embryo itself.[1] As the embryo develops into a fetus, the tail is absorbed by the growing body. The developmental tail is thus a human vestigial structure.[2][3] Infrequently, a child is born with a "soft tail", which contains no vertebrae, but only blood vessels, muscles, and nerves, although there have been a very few documented cases of tails containing cartilage or up to five vertebrae. Modern procedures allow doctors to eliminate the tail at delivery. Some of these tails may in fact be sacrococcygeal teratomas. The longest human tail on record belonged to a twelve-year-old boy living in what was then French Indochina, which measured 229 mm (9 inches). A man named Chandre Oram, who lives in West Bengal, a state in India, is famous because of his 13-inch (330 mm) tail. It is not believed to be a true tail, however, but rather a case of spina bifida.
Humans have a tail bone (the coccyx) attached to the pelvis, in the same place which other mammals have tails. The tail bone is formed of fused vertebrae, usually four, at the bottom of the vertebral column. It doesn't protrude externally, but retains an anatomical purpose: providing an attachment for muscles like the gluteus maximus.
