It turns out chimps at the zoo insist on repeatedly hurling their faeces at me because they're geniuses and not just because it's hilarious. Seriously. Scientists studied chimp throwing and developed the following axiom: the frequency and accuracy with which a chimpanzee throws objects is directly correlated to its intelligence.
How did we learn this incredible piece of knowledge? Researchers at the National Primate Research Center spent an inordinate amount of time watching chimps throw all orders of things at each other. They compared data about how often and accurately monkeys hurl stuff to brain scans of the animals. Low and behold the best, most frequent throwers also exhibited increased activity in the motor cortex, and more connections in the areas of the brain which in humans are responsible for speech. In other words these chimps are more intelligent.
The scientists say that in chimps, throwing is a form of tool usage for communication and that those that do it the best don't just have better motor skills — they also have a better capacity for communication. Think about it: Unlike humans, our closest cousins can't talk so they chuck stuff to get each other's attention. (It stands to reason that sometimes the only disposable throwing object would be a big handful of bodily waste.) When humans and chimps split from their common ancestor, "there was intense selection on increased motor skills associated with throwing" and along with that, the beginnings of a brain that would eventually be capable of speech.