Learn about Koko, the gorilla who redrew the line between people and animals for more than 40 years. In 1971, Penny Patterson began teaching sign language to Koko, unaware that this relationship would define both their lives.

Watch Koko: The Gorilla Who Talks, tonight at 7pm on WGBH WORLD


Credit: Courtesy of © 2015 The Gorilla Foundation / Koko.org Photo by Ron Cohn