US researchers have identified the genetic mutation responsible for humans losing their tails.

Researchers from New York University Langone Health and Tandon School of Engineering note that the TBXT gene has a mutation in humans that caused their tails to disappear nearly 20 million years ago.

According to the researchers, humans have tails when they are fetuses, but they lose them and fuse into the vertebrae to form the coccyx bone.

And according to the American newspaper, “The New York Times”, the loss of the mentioned gene came to adapt to possible neural tube defects.

Scientists are not yet clear about the mechanisms of the exact genetic changes that lead to tail loss in humans, precluding an understanding of how tail loss affects other human evolutionary events, such as bipedalism.

In their study, the results of which were published on the bioRxiv website, which specializes in publishing scientific research, the researchers identified 31 genes in different species for developing tails, and after comparing them, they discovered the role of the mutation in the disappearance of tails in humans.

To confirm their findings, the researchers used genetically modified mice to see if the TBXT mutation was responsible for the appearance of the tail. They found that most fetuses did not develop tails except for one case, where the fetus developed a very short tail.