Who's Your Cousin?

The great apes are among the most popular animals in most zoos. Their actions, facial expressions, and family life remind us so much of ourselves. Have you ever wondered, though, how we might look to them?

- By Stephen Whitt

A modern, statistically based system of classification called cladistics reveals a surprising possibility: Not only are humans apes, but we are more closely related to chimpanzees than chimpanzees are to orangutans or gorillas. In other words, the chimpanzees’ closest living relatives are—us! A gorilla, looking past our culture and technology, might see us humans as just another type of chimpanzee.

Cladistics is a mathematical representation of a simple idea—that all living things are related. The more they are related, the more recently they had a common ancestor. These relationships are expressed in diagrams called cladograms.

The simplest cladogram links two living things—you and a chimpanzee, for instance. The diagram doesn’t seem to display much information, as there’s only one way to draw it. You and a chimpanzee have a lot in common, sharing among other traits four limbs, hair, a big brain, and almost 99 percent of your DNA. In other ways, you and a chimpanzee are different. That’s why you appear on separate branches of the cladogram, after all!

The interesting questions arise when we add a third living thing to the cladogram—let’s say a gorilla. There are three different ways to draw this relationship. How do we decide among them?