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 determined that it all came down to a single fragment of DNA that apes and humans share, but that is missing in monkeys.
The discovery lies in the TBXT gene, which is involved in tail length in certain animals, and when a small piece of DNA called AluY was inserted, the tails were lost.
Although the reason for the loss of its tail is uncertain, some experts propose that it may live better on the ground than in trees.
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.
The study’s corresponding author, Bo Xia, said: “Our study begins to explain how evolution eliminated our tails, a question that has intrigued me since I was young.”
Previous work had linked more than 100 genes to tail development in several vertebrate species, and the study authors hypothesized that tail loss occurred through changes in the DNA code of one or more of they.
AluY fragments are also called “jumping genes” or “mobile elements” because they can move and insert themselves 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, the researchers identified two jumping genes in TBXT found in great apes, leading to the hypothesis that AluY had been randomly inserted with the code tens of millions of years ago.
To unravel the mystery, researchers inserted jumping genes into mice and discovered that the offspring’s tails were completely missing.
The team also discovered that the jumping gene altered tail length in one of the mice.
To unravel the mystery, researchers inserted jumping genes into 63 mice and found that the offspring’s tails were shorter or missing altogether.
Any advantage that arose from the loss of tail was likely powerful, the researchers said, because it may have occurred despite having a cost.
Specifically, the researcher found a small increase in neural tube defects in mice with the study’s insertion in the TBXT gene.
Furthermore, an AluY insertion remained at the same location within the TBXT gene in humans and apes, resulting in the production of two forms of TBXT RNA.
And one way is likely contributing to the loss of the tail.
Professor Jef Boeke, from New York University Langone Health, said: “This finding is notable because most human introns carry jumping, repetitive copies of DNA with no effect on gene expression, but this particular insertion of AluY did something as obvious as determining the length of the tail.”
The discovery lies in the TBXT gene, which is involved in tail length in certain animals, and when a small piece of DNA called AluY was inserted, the tails were lost.
Gorillas, chimpanzees and humans are thought to have lost their tails when they moved away from Old World monkeys, the researchers said.
After this evolutionary split, the group of apes that includes modern humans developed the formation of fewer tail vertebrae, giving rise to the coccyx or coccyx.
Although the reason for the loss of its tail is uncertain, some experts propose that it may be better adapted to life on the ground than in trees.
The famous naturalist Charles Darwin discovered the change in human anatomy and that of our ancestors in his 19th century book The Descent of Man, but he could not be sure that the coccyx was an ancient tail.
“I believe that Os coccyx provides attachment to certain muscles, but I cannot doubt that it is a rudimentary tail,” Darwin wrote.