Koko the signing gorilla died last spring at the age of 46. She had a rough childhood, and was fostered by Francine Patterson, who taught her sign language. Scientists who are skeptical about animal communications say we are over-interpreting his language, but to those who knew Koko best (including Robin Williams), Koko offered a window into the life experience and even the metaphysics of another kind of creature.
Patterson got the idea originally from Koko. Koko taught Patterson her own sign language, already acquired in his childhood from other gorillas in the San Francisco Zoo. Patterson was impressed, and decided to continue and deepen the communication between them.
Patterson was a grad student when she was assigned to care for Koko. Koko became her career for the next 46 years.
Koko had an active vocabulary of about 2,000 words, comparable to a kindergartener. Like a child, Koko had a far larger passive vocabulary, and we can only guess how much she understood. Patterson habitually talked to her in ordinary English, and reported that she understood the gist of most English language conversations around her, though she lacked the mouth parts to speak herself.
Koko called herself "Queen", picking up the word from occasional usage in her presence. She loved cats and nagged her owner for a pet. She kept a pet kitten for just a few months before it was run over by a car, and then mourned her pet's death as we might.
Koko learned to play the recorder, and anticipated her birthday each year. Her best friend was Michael, another gorilla, who was orphaned in the wild when poachers cruelly murdered his mother. Michael used sign to bear witness to this crime. Michael had nightmares from PTSD, and he told Koko about them.
Koko had a lot to tell humans, but she did so on her own schedule, and didn't respond well to interrogation. She did respond to attention with a penetrating gaze from the window of her gorilla soul.