Science & Technology

How our ape ancestors suddenly lost their tails 25 million years ago


Wild chimpanzee walking in the woods

Shutterstock / Alexwilko

About 25 million years ago, our ancestors lost their tails. Now geneticists may have discovered the exact mutations that prevent apes like us from growing their tails-and if they are correct, this loss is not a gradual shrinkage of the tail. It happened suddenly.

“I lose my tail all at once.” Itai Yanai At NYU Langone Health in New York.

His colleague Boshaa He says he was wondering why people didn’t have a tail like other animals when he was a kid. “When I was little, this question was in my head,” he says. “I was asking,’Where is my tail?'”

Recently, the coccyx of Xia, a small bone at the base of the spine that is a trace of a mammal’s tail, was injured in a car accident. “It was really painful,” he says. “It kept reminding me about the tail part of our body.”

That’s why Xia has begun investigating Genetic basis Of tail loss. Mutations involved in tail loss should be present in apes, not monkeys. He and his colleagues compared ape and monkey versions of 31 genes involved in tail development.

Since they found nothing in the protein coding region, Junk DNA It is in the gene. Thinking of proteins as flat-pack furniture, the genetic guidance booklet for making proteins has many Gibberish pages that must be removed before the instructions work. These extra bits, called introns, are cut from the mRNA copy of the gene before the protein is made.

Xia found the ancestors of apes, TBXT, NS Aluminum element I landed a smack van in the middle of the intron. Aluminum The element is a genetic parasite, Copy and paste by yourself The entire genome. “We have one million people Aluminum Elements scattered throughout our genome, “says Yanai.

generally, Aluminum No difference in Intron – it’s Edit with intron..But in this case there is something else Aluminum Closer elements, but in reverse order. Because the two sequences are complementary, Xia recognizes them and they bind together to form a loop in the mRNA.

This effectively glues several pages of the instruction manual. In other words, if extra pages are cut off, some instruction manuals are often lost. This means that the assembled furniture (TBXT protein) often lacks important parts.

The team conducted several experiments to demonstrate this. For example, they showed that mice with this mutation, like apes, produced a mixture of full-length and missing bits of TBXT protein, which usually resulted in complete tail loss.

“It’s very important that something is lost in one big burst, because you don’t have to assume that millions of years of continuous small changes will gradually build up,” he says. Carol Ward At the University of Missouri. “If you look at apes, you may find out why they are sudden. [emerge] They don’t have a tail, “she says. There is no evidence in the fossil record that the tail length is slowly decreasing, but for now, Ward says the fossils are too low to be excluded.

The reason our ancestors have lost their tails is that the findings cannot tell us. That is why this mutation was chosen by evolution.Most proposed explanations include a tail that is disadvantageous when early apes begin to move in other ways, such as: Upright walking On the branch. But fossils suggest that the first tailless ape was still walking on all fours, Ward says.

Xia and Yanai believe that this mutation also has its drawbacks, so there must have been a strong advantage in losing its tail.A few Mice developed spina bifida-like spinal abnormalities. They speculate that the relatively high proportion of spina bifida in people is a protracted relic of the loss of our tail millions of years ago.

See also: bioXriv, DOI: 10.1101 / 2021.09.14.460388

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How our ape ancestors suddenly lost their tails 25 million years ago How our ape ancestors suddenly lost their tails 25 million years ago

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