Scientists have found Answers to Why Humans don’t have Tails.

Humans are special, but we’re missing something common in many animals with spines: a tail. Why this is has been a bit of a mystery.

Tails are helpful for balance, moving, talking, and protecting against bugs that bite. But humans and our closest ape relatives said goodbye to tails around 25 million years ago, when we split from Old World monkeys. People thought losing tails was because we started walking on two legs, but we didn’t know much about the genes that caused it.

Now, scientists have found out that a small piece of genetic code, called an Alu element, is the reason we lost our tails. This code was thought to be useless for a long time. They found this code in a gene called TBXT, which controls tail length. Alu elements can move around in our genes and cause or fix changes.

An Alu element called AluY

A long time ago, an Alu element called AluY moved into the TBXT gene in our ancestors, including great apes and humans. Scientists checked the DNA of six great ape species and 15 other primates. They found AluY only in great apes, as reported in Nature on February 28. In tests with changed mice genes, altering Alu insertions in the TBXT genes led to different tail lengths.

Before this study, many ideas tried to explain why great apes became tailless. One common idea linked it to walking upright and evolving to walk on two legs. Bo Xia, the main researcher from the Broad Institute of MIT and Harvard University, said this.

Before, no one knew exactly how humans and great apes lost their tails. Bo Xia said, “Our finding is the first to suggest a genetic reason.”

Since tails are connected to the spine, this discovery could also help us understand problems with the neural tube during human baby growth.

Extremely Rare

A big discovery happened for the researchers when Xia looked at a part of the genome called TBXT on a popular online database used by scientists studying how organisms grow. This was mentioned by Itai Yanai, who works at the New York University Grossman School of Medicine.

Alu elements are common in human DNA, and the insertion in TBXT is very rare, like finding one specific thing among a million others in our genetic code, according to Yanai. Despite many scientists thinking the Alu insertion in TBXT was useless DNA, Xia saw that it was close to another Alu element. He thought that if they joined together, it might cause a problem in making proteins in the TBXT gene.

“It was a quick realization. Then it took four years of studying mice to check if it was true,” Yanai explained.

The Use of CRISPR Tool

In their tests, the scientists used a tool called CRISPR to change genes in mice, adding the Alu part into their TBXT genes. They discovered that Alu caused the TBXT gene to make two types of proteins. One of these proteins resulted in shorter tails: the more of this protein the genes made, the shorter the tails became.

This finding adds to the growing evidence that Alu elements and similar jumping genes might not be useless as previously thought, Yanai explained. “While we know how they copy themselves in the genetic code, we now have to consider how they also affect important parts of the body, like how it looks and grows,” he said. “It’s surprising that one tiny Alu element can lead to losing a whole part of the body, like the tail.”

Xia mentioned that people haven’t fully understood how Alu works in changing how genes function, even though it’s quite effective and easy.

“I’m finding that the more I learn about the genetic code, the more I see how much we still don’t know,” Xia said.

Leia o Artigo Original CNN

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