Though the proverb warns that "people who live in glass houses shouldn't throw stones," it makes no mention of primates in zoo exhibits. Santino, a 30-year-old chimp in Sweden's Furuvik zoo, has been doing just that for 14 years now, angrily launching rocks and discs of concrete into crowds of tourists, New Scientist reported on their website in March.
What's more fascinating than his aggressive stone throwing is the calm and calculated way in which he collects them beforehand. Some scientists say that, just like humans, this behavior proves chimps are capable of planned action, unmotivated by their current emotional state.
"These observations convincingly show that our fellow apes do consider the future in a very complex way," Mathias Osvath of Sweden's University of Lund told New Scientist. "It implies they have a highly developed consciousness, including life-like mental simulations of days to come. I would guess that they plan much of their everyday behavior."
Mary Lee Jensvold, associate director of the Chimpanzee & Human Communication Institute and board member of Animal Welfare Institute agrees: "Language, tool use, theory of mind, and now planning—all abilities that were imagined to be unique to humans. Ethologists are discovering that humans are just not that different."