Scientists have solved the mystery of humanity losing its tails 25 million years ago

Our ancestors lost their tails about 25 million years ago, but scientists have recently discovered what caused the mutation that changed the course of primate history. Researchers at New York University have determined that it all comes down to one piece of DNA that is common to great apes but absent from apes.

The discovery involved the TBXT gene, which in some animals is linked to tail length, and when a small piece of DNA called AluY was inserted, the tails were lost, the Daily Mail writes.

Although the reason for the loss of the tail is unclear, some experts suggest that it may be better suited to life on the ground than in trees.

Bo Xia, the author of the corresponding study, says: “Our research begins to explain how evolution robbed us of our tails, a question that has interested me since childhood.”

Past work has shown that more than 100 genes have been linked to tail development in various vertebrate species, and the study authors hypothesized that tail loss occurred due to changes in the DNA code of one or more of them.

AluY fragments are also called “jumping genes” or “transposable elements” because they can move around and be inserted repeatedly and randomly into human code.

The elements are also responsible for the regulation of tissue-specific genes and can change the way a gene is expressed.

In the new study, researchers identified two jumping genes in TBXT that are found in apes, leading to the hypothesis that AluY accidentally inserted itself into the code tens of millions of years ago.

To solve the mystery, the researchers injected jumping genes into 63 mice, finding that the offspring’s tails were either shorter or completely absent.

Any benefit associated with tail loss was likely significant because it could occur despite the costs, the researchers said.

Specifically, the researcher found a small uptick in neural tube defects in mice with the study’s insertion in the TBXT gene. Moreover, the AluY insertion remained at the same location in the TBXT gene in humans and monkeys, resulting in two forms of TBXT RNA. And one of the shapes likely contributed to the loss of the tail.

Professor Jeff Boeke from NYU Langone Health comments: “This discovery is remarkable because most human introns carry copies of repetitive, jumping DNA without any effect on gene expression, but this particular AluY insertion did something as obvious as determining tail length.” .

Gorillas, chimpanzees and humans are believed to have lost their tails when they split from Old World monkeys, researchers say. After this evolutionary split, the group of great apes that includes modern humans evolved to form fewer tail vertebrae, resulting in the coccyx, or coccyx bone.

Famed naturalist Charles Darwin discovered changes in the anatomy of humans and our ancestors in his 19th-century book The Descent of Man, but could not be sure that the coccyx was an ancient tail.

“I believe that the coccyx provides an attachment to certain muscles, but I have no doubt that it is a vestigial tail,” Darwin wrote.