Philosophers and anthropologists have long debated over what makes human beings different from other creatures. It isn't our ability to build houses: birds and beavers build houses. It isn't our use of tools, either. Many animals use tools. Even a simple gull can employ a rock to open a shell. We aren't different because we organize into societies. Ants have an elaborate social structure, including "hospitals" for their sick and "nurseries" for their young. Nor is it the use of language that sets us apart. Whales and dolphins have an elaborate language, too. It isn't even our larger brain. Dolphins' brains are bigger than ours are, in comparison with their bodies.

There are lots of things human beings have in common with other creatures. But one thing that sets us apart is the act of reme…