We all know gorillas are capable of some pretty extraordinary, human-like behaviors, and now one of the most extraordinary gorillas that helped us understand this has sadly passed away. Koko the gorilla, who mastered sign language, died on Tuesday at age 46. In a release, The Gorilla Foundation said “Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy. She was beloved, and will be deeply missed.”

Koko was a western lowland gorilla born at the San Francisco Zoo in 1971. She learned sign language early in her life, enjoyed reading and being read to, and even purred at parts of books she particularly enjoyed. She also had an affinity for kittens, showing them a matronly care, and was widely known for her tenderness. She was said to have understood about 2,000 words of spoken English, and could actually follow conversations.

She was, perhaps, the first gorilla celebrity, having made friends with Robin Williams and TV’s Mr. Rogers, appearing in several documentaries, and twice featuring on the cover of National Geographic. She also dabbled in the art world, having painted a few pictures that are now available for purchase.

Although her passing is sad, there’s no denying her impact on research efforts to better understand gorillas, their emotional capacity, and cognitive abilities.

H/T: CNN