"To find out how and why humans lost their tails, Xia and his colleagues examined the early stages of embryonic development, during which certain genes are switched on and off. Those genes control the formation of different parts of a skeleton.
Scientists had already identified several genes fundamental to tail development in other animals, so the study authors suspected a genetic mutation, or a combination of them, might have erased tails in our ancestors. They compared the DNA of six species of tailless apes, including humans, to 15 species of tailed monkeys to find a mutation that apes and humans share, but monkeys lack. Eventually, their search led them to a gene called TBXT."
Why Don’t Humans Have Tails? An Old Genetic Mutation Could Explain Why Monkeys, but Not Apes, Have the Extra Appendage
Scientists had already identified several genes fundamental to tail development in other animals, so the study authors suspected a genetic mutation, or a combination of them, might have erased tails in our ancestors. They compared the DNA of six species of tailless apes, including humans, to 15 species of tailed monkeys to find a mutation that apes and humans share, but monkeys lack. Eventually, their search led them to a gene called TBXT."
Why Don’t Humans Have Tails? An Old Genetic Mutation Could Explain Why Monkeys, but Not Apes, Have the Extra Appendage