Why don't humans have tails? Genetic discovery may explain

Why don't humans have a tail? This question served as the basis for a study developed by NYU Langone Health and published on Wednesday (28) in nature. Researchers have identified a DNA mutation that caused our ancestors to lose their tails.

The tail can help animals in different situations, following different functions. It can be used as a way to communicate feelings and intentions (like a dog wagging its tail when it's happy and putting it between its legs when it's afraid).

The tail can also play a role in balance during movement, especially in situations such as running or jumping. But humans do not get this help from nature.

Continues after ad

Why don't humans have a tail?

The study showed that humans do not have a tail due to a mutation in the TBXT gene, which is known to be associated with tail length in some animals. Scientists have identified two elements in this gene called Alu – repetitive DNA sequences – which are found in great primates, but not in apes.

According to the study, these elements are not in the part of the gene that codes for proteins, but rather are present in DNA sequences called the dark matter of the genome, where they are removed before the molecule is converted into a protein.

The authors say they analyzed other genes associated with tail length, but the case of the Alu elements in the TBXT gene was subtle. They discovered that a related RNA molecule could be cut in several ways to generate multiple proteins from the same gene.

Continues after ad

“In comparison, mice produce only one copy of the protein. The presence of both copies appears to prevent tail formation,” the researchers hypothesize.

Is there a human with a tail?

Currently, the only traces of the tail in humans exist in the form of a small bony structure at the base of the spine: the famous coccyx.

Continues after ad

It is very rare, but there are cases of some humans being born with some type of tail. In 2021, a Brazilian was born with a tail 12 cm long and a ball at its tip, which was described as a “change in the retraction of the fetal tail,” since as the fetus develops, the tail retracts, which did not happen in 2021. This issue.

In 2022, in Mexico, there was also a case of a baby born with a furry tail 6 centimeters long. Doctors performed a removal operation.

Hence, humans do not have a tail due to factors such as genetic mutation highlighted by the study. We can see that this loss was the result of a change in the lifestyle and environment in which our ancestors lived.

source: nature