In the early stages of development of a human embryo, there's a tail-like structure. This tail measures about 1/6th the size of the entire length of the embryo (the equivalent of a 12-inch tail on a 6-foot man). But as the fetus develops, the tail is absorbed. Enzymes dissolve the bones, and the entire structure retracts into the fetus's body.
If something goes wrong in the process, the tail may continue to grow.
The baby is normal overall. But it has a tail and will probably grow up to be evil.
The tail is a "caudal appendage", basically a vestigial muscle. It can be removed surgically.
If left intact, it may continue to grow along with the rest of the body.
Unlucky Xiao Wei is a seven month old boy from Guangdong, China. He was born with a large tail, and surgeons can't remove it.
Wei was born with myelomeningocele, a variant of spinal bifida. Spina bifida, or split spine
is a fault in the development of the spine and spinal cord which leaves a gap in the spine. Myelomeningocele spina bifida causes the spinal column to remain open allowing the membranes and spinal cord push out to create a sac in the baby’s back. This sometimes leaves the nervous system vulnerable to infections that may be fatal.
Even when the tail can be surgically removed, the nervous system will probably already be permanently damaged, resulting in a range of symptoms, including paralysis and incontinence.
Chinese doctors say the growth at the base of Wei's spine has been caused by damage to the outer wall of the child's spinal canal. Surgeon Huang Chuanping reported, "Wei's growth is quite well developed and now measures some 10 centimeters. If we cut it off it will simply grow again. We need to repair the spinal canal first to stop it reoccurring."