We finally know why humans don’t have tails

Scientists have pinpointed a genetic mutation responsible for the loss of tails in the ancestors of humans and apes, a change that occurred around 25 million years ago. The mutation is found in the TBXT gene, which influences tail length. The discovery was led by Bo Xia at the Broad Institute, who became intrigued by the origin of the tailbone after an injury.

The study, published in Nature, reveals that two Alu elements—repetitive DNA sequences unique to primates—inserted into the TBXT gene of great apes but not monkeys, disrupt the gene’s function. These elements, located in non-coding regions called introns, cause an exon to be removed during RNA processing, altering the protein produced and preventing tail formation. This process, known as alternative splicing, contributes to the complexity of human physiology.

The team’s experiments with mice demonstrated that inserting these Alu elements resulted in tail loss and an increased risk of spina bifida, a birth defect. This finding suggests that the genetic mutation not only contributed to tail loss but may also have facilitated bipedalism in humans. The research underscores the significant impact of such mutations on evolution and opens up new avenues for understanding the genetic roots of various traits.
Read more at livescience.com…