Humans’ closest primate relatives lost their tails about 25 million years ago, but exactly how has remained a mystery. A breakthrough in genetic research may finally offer answers.

Many people believe that dogs wag their tails when they are happy. But, according to a new study, the behavior is actually much more nuanced than that.

A newly discovered genetic mechanism helped eliminate the tails of human ancestors. Skip to main content. Scientific American. February 28, 2024. 4 min read. How Humans Lost Their Tails.

The findings flip the long-held belief that dogs wag their tails when happy, and instead suggest tail wags made people happy, so we selected for the trait.