Kanzi the Bonobo, who learned language and made stone tools, dies at age 44

What we learned about ape and human cognition from Kanzi the Bonobo, who died this week

Kanzi the bonobo, who learned how to communicate with humans using symbols, has died at the age of 44. Raised and kept in captivity, Kanzi was the subject of many studies aimed at illuminating ape cognition and the origins of human language and tool use.

Why it matters

Kanzi was not the first great ape to learn how to communicate with humans using symbols. Koko the gorilla and Washoe the chimpanzee learned signs that were adapted from American Sign Language. But unlike his predecessors, who acquired their skills through direct training from researchers, Kanzi developed an interest in such symbols on his own when his adoptive mother, Matata, was receiving lessons on how to use keyboard lexigrams to communicate. Kanzi went on to learn hundreds of symbols that represented various objects and activities, as well as some more abstract concepts. Sometimes he combined these symbols to create new meaning.

Kanzi was also something of a technologist. Archaeologists Nicholas Toth and Kathy Schick, both at Indiana University, began working with Kanzi in 1990 to teach him and his sister Panbanisha how to make stone tools by using one rock as a hammerstone to remove sharp flakes from another rock called a core. "Kanzi slowly got more adept at flaking stone through time," Toth recalls. Early in Kanzi's training, he invented his own technique for making stone tools, throwing a flint cobble against a hard tile floor to remove larger flakes. He would then use the flakes to cut a cord to open a box with a food treat inside. After developing this technique, Toth says, Kanzi "seemed to realize that the force of impact was important in getting larger usable flakes" and applied this newfound knowledge when he resumed using the hammerstone-and-core technique to make tools.

Kanzi's toolmaking skills fell short of those of modern-day humans and our ancestors, however. When Toth and Schick compared Kanzi and Panbanisha's handiwork with their own and that of human ancestors who lived 2.6 million years ago, they found that the bonobos had many more failed attempts at removing flakes from the cores--and that the flakes the bonobos did produce were smaller than the ones made by humans. "We feel that their limitations in flaking were both biomechanical and cognitive," Toth says. "You have to recognize acute angles on core edges and strike in the right place and at the right angle with your stone hammer to successfully remove flakes."

What the experts say

Primatologist Jill Pruetz of Texas State University, who studies wild chimpanzees in Senegal, shared her memories of Kanzi on Facebook: "I was lucky enough to meet Kanzi a few times & even got to hold a conversation with him via his symbol board and got to play chase with him too," she wrote. "He had a hard time understanding my spoken words only if it was a word that had a soft 'a' sound in it, which I blame on my Texas accent."

One of Pruetz's favorite pieces of Kanzi lore, she added, was a story about him using two of his symbols to describe a frightening beaver he discovered in his new outdoor habitat in Iowa. "He combined the symbols for 'water' and 'gorilla,' the latter referred to something scary in his world, and I always think of beavers ... as water gorillas now," she wrote.

More about Kanzi

Kanzi was born in 1980 at what is now the Emory National Primate Research Center Field Station. He and Panbanisha were moved to the Language Research Center at Georgia State University in 1985. From there the siblings were sent to the Great Ape Trust in Des Moines, Iowa. That research facility eventually closed amid accusations of animal neglect, among other troubles, shortly after Panbanisha died there in 2012. The Ape Conservation and Cognition Initiative (ACCI) took over the facility in 2013. On March 19, 2025, the ACCI announced that Kanzi had died on March 18. According to the ACCI, Kanzi hadn't shown any signs of illness that day and had spent the morning foraging for breakfast, chasing his nephew Teco and enjoying enrichment surprises before settling in for a grooming session and becoming unresponsive. Kanzi's cause of death is unknown; necropsy results are pending. He was being treated for heart disease.