Published on: 03/29/2024 – 14:10 Last updated: 03/29/2024 – 14:15
After years of research and questions, American researchers succeeded in identifying the mechanism that caused humans and great apes to become tailless, unlike many vertebrate animals. According to a study recently published in the journal Nature, a genetic mutation in the TBXT gene, which is known to control tail length, led to the loss of the tail. It is believed that this mutation occurred 25 million years ago in apes, from which the great ape family later emerged.
Most vertebrate animals have a tail that is very useful for maintaining their balance, helping them move and communicate with their peers, and also keeping insects away from them. But humans and great apes such as chimpanzees or gorillas do not have a tail. How and why? Two questions have always puzzled researchers. It is believed that the loss of the tail occurred twenty-five million years ago. Traces of the tail are still visible in humans through the bone called the coccyx in French and English. The tail also appears clearly in the fetus in its mother’s womb in the first weeks, before it gradually shortens and disappears around the eighth week of pregnancy.
Scientific theories indicate that the loss of the tail helped to gain the characteristic of walking on two legs, so-called bipedalism. However, until the completion of the new study, we did not know how the loss of the tail occurred in practice within the body’s cells, at the level of DNA and genes, which are the engines of evolution.
“Garbage DNA”
The study was recently published in Nature magazine The long-standing scientific study, through which American researchers identified a genetic mutation, which is a change in a part of the DNA, is only found in great apes and humans. This mutation was identified thanks to one of the study supervisors from the Gene Regulation Observatory, affiliated with the Massachusetts Institute of Technology and Harvard University. The researcher looked at a part that scientists have long neglected, which is “garbage DNA,” as it is called, or “non-coding DNA.” These are parts of genes spread throughout the DNA in cells that were thought to have no role in influencing the characteristics of the body.
Geneticist Bo Xia looked at the gene responsible for the tail, which is called TBXT, and noticed that in great apes, next to the TBXT gene there is a non-coding gene, unlike other animals that have tails. This gene, when inserted next to the TBXT gene, appears to disable the part responsible for tail growth.
Mice also lose their tails
To confirm this, the researchers conducted experiments in mice that lasted four years. They genetically modified mice. As we know, mice have tails thanks to the gene responsible for this (TBXT). But when the researchers inserted the inactivated gene that we talked about next to it in a simulation of the mutation found in great apes, the mice’s tails began to shorten little by little until they disappeared completely, as we see in the picture. This is the first experiment to provide conclusive evidence of tail loss.
Effect of genetic modification experiment on mice © NATURE magazine
The scientific study showed that the precise understanding of the mechanisms of DNA, its various components, and its relationship to the evolution of organisms is not yet complete, especially regarding the role of garbage DNA, which, according to some researchers, represents nearly half of our DNA. Upcoming discoveries promise more surprises.
