All humans are created with a small tail that is later absorbed by the body and developed into the tailbone. In some rare cases, small amounts of tissue are left hanging on the tailbone area of the body. Most often, the small piece of skin contains no bones, but does contain nerves and blood vessels. In some rarer cases, there are up to five vertebrae in the small tail – resulting in a true human tail or vestigial tail.
The true human tail is not really a tail at all, according to experts. It is thought to be linked to spina bifida or a hiccup in the natural human development process. Typically, white blood cells degrade vertebrae six to 12 in the 8th week of gestation. The 4th and 5th vertebrae are shrunk during the process and eventually skin covers the new spinal cord. If white blood cells do not absorb the latter vertebrae 100%, a tail could be left.
The longest known tail is 13 inches long and belongs to a man in India.