A surprising number of people don't much care about science, and just don't believe we're as closely linked to chimpanzees as we are. You've probably heard it all before - many studies come up with the same result. Most recently, scientists from the Wayne State University, School of Medicine, Detroit, examined key genes in humans and several ape species and found our "life code" to be 99.4% the same as chimps. And chimpanzees can be transfused or blood and live, and visa versa.
However, if that's not convincing - consider behavior. Only one other creature on earth plans and then stages attacks with the intent to do harm for entertainment purposes only - of course, that's us....and also chimpanzees. Consider, Santino, a male chimpanzee at the Furuvik Zoo in Sweden, who plans and then - given the chance - carries out complex attacks on zoo visitors.
At first Santino was famous for throwing rocks and other projectiles at visitors. Now he has improved his technique, which requires spontaneous innovation for future deception. Researcher Mathias Osvath, lead author of a paper about Santino in PLoS ONE, explained what the clever chimp did: "After a visitor group had left the compound area, Santino went inside the enclosure and brought a good-sized heap of hay that he placed near the visitor's section, and immediately after that he put stones under it."
The calculated surprise attacks on visitors demonstrate very advanced thinking usually only associated with humans.
Various animals have been known to "attack" visitors in zoos - from a recent YouTube video of a lion who probably want to make a lunch out of a young visitor, charging the glass....to Bonobos throwing feces in the direction of zoo guests. This is different, though, because the chimp is clearly thinking about an attack days in advance, and then proactively hiding the cache of weaponry. What's more, the array of items to be hurled at visitors don't come with directions - Santino is being creative, even innovative to think about what he might use.
Why does Santino do it? No one knows for sure, of course. Does he really want to harm people? Does he hold a grudge? (because he's in a zoo).... Or does he just get off on the responses of people?
Michael Huffman of Kyoto University's Primate Research Institute has also studied chimp stone throwing, which he believes "may serve to augment the effect of intimidation displays." He further thinks that research on the behavior could shed light on the evolution of stone tool use in humans.