Recent research has revealed that great apes possess mental capabilities once thought to be uniquely human, including imagination and rational thinking. A study published in Science in February documented the first empirical evidence of pretend play in a bonobo named Kanzi, who participated in imaginary tea parties at the Ape Initiative facility in Des Moines, Iowa, in 2024. Kanzi, who died last year, correctly identified a pretend cup of juice in 34 out of 50 trials and chose real juice over pretend juice in 14 out of 18 trials, demonstrating an ability to envision a reality beyond the physical present.
These findings challenge long-held beliefs about human uniqueness. Amalia Bastos, a comparative psychologist at the University of St Andrews and lead author of the study, noted that scientists often propose reasons why humans are special, but testing frequently shows that animals are capable of secondary representations or imagination. The study adds to a growing body of research over the past decade that has uncovered robust similarities between ape and human behaviours.
Other stunning findings include chimpanzees and bonobos remembering past groupmates for decades, chimpanzees rationally revising beliefs when presented with stronger evidence, and various ape species engaging in playful teasing, cooperation across social borders, and even a fascination with crystals. Significant progress has also been made in understanding apes' theory of mind—the ability to understand that others have their own thoughts and beliefs—once considered a distinctly human trait.
Christopher Krupenye, a cognitive scientist at Johns Hopkins University, described the past few decades as transformative, with research pointing to chimpanzees and other apes being extremely sensitive to their social partners. He noted that 30 years ago, the dominant view was that there was no evidence of such capacities, but today the consensus recognises an exciting capacity in these primates.
Despite these cognitive similarities, the other seven great ape species are struggling to survive, unlike Homo sapiens, which has grown to a population of 8 billion. Scientists continue to explore the full cognitive potential of our closest relatives, who diverged from a common ancestor between 6 million and 9 million years ago.
