Rock throwing is a traditional hunting technique used by Aboriginal Australians. Think about the scale economies. You have a tribe of 10 individuals all throwi

Rock throwing is a traditional hunting technique used by Aboriginal Australians. Think about the scale economies. You have a tribe of 10 individuals all throwing rocks at a single being without having to close distance and risk injury. It also appears to me to be a simpler invention for evolution than club usage and therefore more likely as an intermediate step, requiring less cortex. Accuracy and dexterity are no so important, just bipedalism and law of large numbers - after N rocks are thrown all you need is one of two connections. This is all rather speculative, though, and I'm mostly talking out of my arse :-)