Is Trade What Makes Us Human?

It's conventional to argue that human intelligence, or tool using, or language, or cooperative spirit are what make us so uniquely successful as a species (depending on one's definition of success). But all of these supposed forms of uniqueness tend to be a little iffy - any number of animals also fit these descriptions, even, to some extent, possessing language. So here's a new, different claim, in line with our economistic times. Matt Ridley's "The Rational Optimist" argues that trade has provided the deepest foundation for what we have collectively accomplished.  It's a compelling claim, though I'm pretty sure it's well established that monkeys have forms of trade, so it may soon end up in the scrap pile, too.