When Francine "Penny" Patterson, a young graduate student in psychology at Stanford, first saw a tiny, undernourished baby gorilla named Hanabi-Ko at the San Francisco Zoo, she had little inkling that the sickly ape would become her constant companion - and the subject of the longest continuous experiment ever undertaken to teach language to another species. But within a year, Project Koko was underway, and in two weeks the gorilla was using correct signed gestures for food, drink, and more. Today, more than 25 years later, Koko - the world's most renowned gorilla - is drawing on a vocabulary of more than 1,000 words.

KOKO FACTS: