The evolution of primate species are divided into hominoids—a group of tail-less primate species that includes gorillas, chimpanzees, and humans—and nonhominoids, which have tails and are more distant primate relatives of humans. The measure of each species’ evolution is measured in “mya,” or million years ago. For the hominoids, homo and pan evolved 6 mya, while gorilla evolved 7 mya, pongo evolved 14 mya, and gibbons evolved 18 mya. For the nonhominoids, old world monkeys evolved 25 mya, new world monkeys evolved 40 mya, tarsiiformes 58 mya, and lemuriformes 63 mya.
Image Courtesy of Biorender
A new study suggests that an ancient genetic change helps to explain why apes and people do not have tails, but monkeys still do. A team of scientists says it may have pinpointed the genetic mutation that contributed to tail loss. When the scientists made this genetic tweak in mice, some of the animals didn’t grow tails, according to a study that was posted on a preprint server last week.
Researchers over time have identified more than 30 genes involved in the development of tails in various species. Scientists are still learning how their unique activity at the end of an embryo gives rise to a tail. The authors of the new study reasoned that our ancestors lost their tails when mutations altered one or more of these genes. To search for those mutations, scientists compared the DNA of six species of tail-less apes to nine species of tailed monkeys. Eventually, they discovered a mutation shared by apes and humans—but missing in monkeys—in a gene called TBXT.
“This question—where’s my tail?—has been in my head since I was a kid,” says corresponding study author Bo Xia, a graduate student in stem cell biology at NYU Grossman School of Medicine. When he brought the finding to his supervisors—Itai Yanai, PhD, director of the Institute for Computational Medicine, and Jef D. Boeke, PhD, the Sol and Judith Bergstein Director of the Institute for System Genetics—they both said, “I nearly fell off my chair.”
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