From this site:
According to this site:
One out of every 16 children is born with defects. Most of these are minor, such as the babies born with tails. When a baby is born
with a tail, the doctors cut it off right away. Most people do not know if they had a tail.
Anyway, I get embarrassed when stuff like this is trotted out as evidence for evolution and try to distance myself from it. Congenital malformations of this type are under the control of (mutant) developmental genes which utilize expression gradients to direct other genes. Over or under expression of these genes result in additional fingers, additional limbs, extra coccyx length and effects of that nature. The presence of a mutation in such a control gene is an indication of more than one developmental problem. In the case of "vestigial tails" other congenital malformations coexist, primarily spinal bifida, not exactly a vestigial condition.
There's no doubt that the same developmental genes play a part in tail development in other mammals as they do in spine formation in humans. But there are a whole series of genes which function together to make a tail. The suggestion with a misnomer such as "vestigial tail" is that these genes are dormant in the human genome, and, rarely, are activated to produce a tail. Such is not the case. If it was, we'd be looking at a larger issue of evolution reversibility and other serious conceptual issues.