Can humans be born with a tail ?

 

In 2021, a surprising piece of information made the headlines : a Brazilian baby was born with a tail. However, this is not a first in the history of medicine. Since the 19th century, several cases of the presence of a tail on humans have been noted and documented.

Why don't humans normally have a tail ?

The question seems incongruous, but we must remember that Man shares common ancestors with apes, which are, with the exception of great apes, equipped with tails. It was when the human species diverged from primates that it experienced the loss of this appendage, of which normally only the coccyx remains.

Researchers don't know exactly why the man lost his tail. Evolution could have favored this disappearance to facilitate upright walking, or to make reproduction easier. In any case, if Man today finds himself exempt from a tail, it is because it is not useful to him to survive in his environment.

All babies have a tail before birth

You have to go back well before birth, in the first weeks after conception, to discover that all fetuses have a tail. This appears between 4 and 6 weeks of pregnancy, and is present in all mammalian fetuses.

Towards the end of the 8th week of pregnancy, the appendix regresses in humans until it forms only a short bone located at the end of the spine, the coccyx. But, in very rare cases, the fetus retains its tail until birth.

Real tail or pseudo-tail ?

Through the several hundred reported cases of the presence of a tail on a human being, doctors have established a difference between real tails and pseudo-tails. The real tail corresponds to that present in animals such as mice, monkeys or cats. It contains fats, muscles, is innervated and can even move. It develops in a healthy way, like any member, and its removal does not therefore pose a problem.

The pseudotail results from a malformation in the vertebrae. It consists mainly of fatty tissue, but it can sometimes take the form of a tuft of hair. Its removal requires more precautions, because it is often located in the continuity of the spinal cord, which involves high-precision surgery.