It is believed that humans once had tails that they used for balance. Now-a-days the tail bone or whats left of it is used by the body for sitting, bowel movements and keeping the anus closed. Just ask someone who has had their coccyx bone removed, how hard it is to sit. Almost impossible!
Did you know that when you were 5-6 weeks old and still a human embryo you had a tail, containing about 10 to 12 vertebrae.
For the next 2-3 weeks the growth of the tail stops and apoptosis (the death of cells naturally by the Wnt-3a gene, takes place) which causes the tail to disappear by 8 weeks. All that is left is the coccyx, which evolution has fused all the vertebrae together. Its attached to the bottom of the sacrum, it's primary purpose now is to anchor muscles.
In some people this apoptosis doesn't kick in and they continue to grow tails called, True Tails. The longest was 13 inches, and could move and contract, belonging to Chandre Oram who lived in West Bengal.
This kid with a tail, is worshiped by thousands and is believed the tail has divine healing powers and such.
There are no bones, cartilage, notochord, or any part of the spinal cord actually going down into these Vestigial tails.
The tails are composed of adipose, muscular and connective tissue, various nerves and blood vessels. There have been some reported cases of newborns with 5 fully developed vertebrae but its rare. In some cases the tail has arisen from complications of Spinal Bifida. These are not true human tails but pseudo tails. There have only been 20 to 30 cases of true vestigial tails reported since the 1800's.
Kei$ha the rock star reportedly told Heat magazine in an interview she was born with a tail.
"I had a tail when I was born. It was a tiny tail, about a quarter of an inch, then they chopped it off and stole my tail. That was when I was little. I'm really sad about that story."
Tails are easily removed by a simple operation, done not long after birth. Sounds like another similar operation babies have. Hmmm...