It’s always been easy to understand why human beings developed technology, poetry, music, agriculture, language, cities and medicine, and other critters didn’t: big brains — full stop. The animal with the best cognitive computer is simply going to do better than all the others, and that advantage tends to build on itself, with the brain upgrading itself with each iteration of the species.
But intelligence is only part of our collective success. You may be the smartest member of your early-human tribe, but if you die without ever telling other early humans all the cool and innovative things you know, those accomplishments die with you. The real key to the steady climb of humanity — what anthropologists call the “racheting” of the culture — is sharing, the democratic distribution of information so that what starts off as personal knowledge eventually becomes community knowledge. Once an idea goes viral that way, everyone can take a crack at improving on it further.