Opinion: Remembering Ai, a remarkably intelligent chimpanzee

23-year-old chimpanzee Ai, known for her ability to recognize some letters and numbers, holds her 35-centimetre-tall newborn male chimp Ayumu, 25 April 2000, at the Primate Research Institute of Kyoto University in Inuyama, central Japan.

We remember Ai, a highly intelligent chimpanzee who lived at the Primate Research Institute of Kyoto University for most of her life, except the time she escaped and walked around campus.

(Image credit: AFP via Getty Images)