Vestigial tail, also known as human tail, is a phenotypic extravagance of which only about 100 cases are known worldwide. It is one of the rarest diseases known so far.
This tail grows in the final area of the sacrum, at the level of the coccyx and is usually composed of connective tissue, muscles, blood vessels, nerve and skin. However, on other occasions, other structures with vertebrae and cartilage may also appear.
The vestigial tail is usually removed as soon as the baby is born. However, on some occasions, this intervention is not done so the adult keeps it throughout his life.
On the other hand, Many cases of vestigial tail have been linked to spina bifida disease, a congenital problem that causes the spinal canals to not close completely during pregnancy.
In addition, studies confirm that cases of vestigial tail are twice as likely in men than in women.
Causes of the appearance of tail tail
The reality is that the cause of this rare disease is not known exactly. Scientists have deduced that comes from a genetic mutation, which reactivates a hidden character of our evolutionary development that has remained repressed in the human genome.
In addition, recent studies and research have been carried out whose results reinforce this theory. In order to verify that these genes were also in the human genome, genes responsible for tail development in mice have been studied and in other vertebrate animals.
Humans no longer develop a tail despite having the genes for it because their regulation causes cell death or apoptosis of the cells that were intended for the development of this vestigial tail.
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In other words, in our body we have enough orders and instructions to develop a queue, however, these orders are destroyed. As a consequence of these genes, a tail can be seen in humans between 4 and 8 weeks of pregnancy.
Due to these few cases of humans with vestigial tail, a lively debate has been opened in the world of medicine and evolution.
You have to keep in mind that, although it is called that, in most cases it is not a queue as such. A normal tail, such as that of a cat or dog, is formed by a series of bones, cartilage, spinal cord and well differentiated muscles that allow its correct movement.
But nevertheless, in the described cases of vestigial tail, there is none of these structures described, and the few muscles that form it, lacking bones to join and insert, will not be able to contract in a coordinated way or move as would the tail of any animal.
However, as we have seen, it is formed by:
All these structures will allow the tail to move and contract at the child's will, yes, without any coordination and with many limitations.
Read also: Epigenetics: what it is and what its implications are
On the other hand, the size of the tail tail varies according to the cases seen. The longest recorded was a while ago in a boy from the then French Indochina. The size of its vestigial tail was 229 mm.
Many times it is difficult to differentiate between spina bifida and vestigial tail. For example, there is a case of an Indian boy named Chandre Oram who became famous for his long "tail." However, this alteration was not a true tail, but a case of spina bifida.