Our very ancient animal ancestors had tails. Why don't we? Somewhere around 20 million or 25 million years ago, when apes diverged from monkeys, our branch of the tree of life shed tails.

Lemurs, lizards, whales — all are famed for their tails in some way. But which animal has the longest tail ... "You could think of it as the long beam that people walking across a tightrope ...