You may have thought things like currency or money are concepts known solely by man - something which differentiates humans from animals. Some might have a sense of ownership, besides of course territory, but trading and the likes haven't been observed in any other species besides homo sapiens. An economist/psychologist duo from Yale back in 2005, however, managed to train seven capuchin monkeys how to use money, and I'm pretty sure from here on some of you might be able to guess what happened from there on.