You can hold on to your butts thanks to DNA that evolved in fish
Evolution has adapted the digits of mammals for an enormous range of uses, from our opposable thumbs to the spindly digits that support bat wings to the robust bones that support the hoofs of horses. But how we got digits in the first place hasn't been entirely clear. The fish that limbed vertebrates evolved from don't have obvious digit equivalents, and the most common types of fish just have a large collection of rays supporting their fins. Despite this uncertainty, we have identified some ge