> and suffered many reverses. I think this is a crucial point. If all of humanity had been wiped out in a famine in Africa fifty thousand years ago, there woul

> and suffered many reverses. I think this is a crucial point. If all of humanity had been wiped out in a famine in Africa fifty thousand years ago, there wouldn't be anyone sitting around today wondering, "Why is it there aren't any civilizations?" And there were probably millenia that went by when the odds of that happening dwarfed the possibility that we might survive long enough to develop a writing system.