Why don't people actually have tails?

And you're in luck, according to a trade journal research team natureLed by biomedical scientist Itai Yanai of New York University. Monkeys without tails may have been better able to stand and sit upright, according to Yanai, a precursor to bipedalism. This would explain why the mutation spread so quickly, leaving great apes like gorillas, chimpanzees and us now without tails.

But other experts have their doubts. “Really nonsense,” calls Fritsen Gales, an evolutionary biologist at the Dutch Research Institute and Natural History Museum Naturalis. “Gibbons and orangutans don't have tails either. They do well in trees.

Moreover, the tail could also be very useful for monkeys that walk upright, two other scientists say in a commentary. nature. “For example, tails support the posture of capuchin monkeys when they move stone tools or walk on two legs.” Tail: No monkey can live without it.

Bad luck in prehistoric times

The loss of our tails may have been the result of bad luck in prehistoric times, when a group of tailless apes isolated themselves by chance and later became the ancestors of all today's great apes. After all, complex organs such as legs, wings and tails have disappeared, and Gales points to a well-known evolutionary rule.

Critics agree that this does not make Yanai's discovery any less interesting. New Yorkers discovered a piece of “jumping DNA” in one of the genes involved in making tails, and it was inserted into it like a kind of pebble. Surprisingly, all tailless monkeys actually have this mutation.

To find out what this meant, Yanai conducted a remarkable experiment: he introduced the mutation into mice. In fact, they did not develop a tail then, or at most it was very short. It appears that the body is no longer able to read the gene called TBXT correctly.

short tail

But Gales doubts whether it is that simple. “It is likely that the tail gradually shortened, and that multiple genes were involved,” she says. “The length of the tail varies in most groups of tailed monkeys.”

For example, bear macaques and Japanese macaques have a very short tail, spider monkeys have a tail that they use as a grasping arm, and western macaques have a long, thin tail. “Tail length, in short, is a trait that changes easily with evolution,” Gales points out. “As long as you still have one.”

In very rare cases, people are also born with a short tail. The idea for a long time was an innocent return to our old building plan. Until doctors discovered that the tail is a serious birth defect, which is usually accompanied by other serious birth problems.