Samuel Pepys (1633–1703), famous for his seventeenth-century diary, wrote about what he called a “baboone” and suggested that it might be taught to speak or make signs. And although it was long known that primates use a number of methods of communication in the wild, early attempts (1900–1930s) to teach primates simple words were failures. A 1925 scientific article suggested sign language as an alternative to verbal language in communicating with primates. In the 1960s, researchers tried to teach chimps and gorillas a modified form of sign language. It began with Washoe the chimpanzee, followed by the gorillas Michael (now dead) and Koko. Washoe learned a little over one hundred signs, but Koko has a working vocabulary of over 1,000 signs and understands about 2,000 words of spoken English.

Elephants—both African and Asian—are the largest land animals on the planet and are also one of the most intelligent. According to research, they are able to express many of the emotions we usually associate with humans, such as anger, self-awareness, play, joy, grief, and love. For example, the animals have a deep emotional attachment to their family members, grieve for the loss of family members, and are almost “psychologically affected” when a family member is killed, for example, by poachers. One of the main reasons for these emotions—and intelligence—has to do with their brains: Elephants have a large and complex neocortex (part of the brain involved in higher functions, such as sensory perception, spatial reasoning, and conscious thought) similar to other intelligent beings, such as dolphins, apes, and humans. They also have one of the largest hippocampuses (when compared to other animals, such as primates and humans)—the part of the brain linked to emotions through the processing of certain types of memory.