Hunter-gatherer societies have typically been egalitarian, as we'll soon see, throughout hominin history. Inequality emerged when stuff, things to possess and accumulate, was invented following animal domestication and the development of agriculture. The more stuff, reflecting surplus, job specialization, and technological sophistication, the greater the potential inequality. Moreover, inequality expands enormously when cultures invent inheritance within families. Once invented, inequality became pervasive. Among traditional pastoralists or small-scale agricultural societies, levels of wealth inequality match or exceed those in the most unequal industrialized societies. Why have stratified cultures dominated the planet, generally replacing more egalitarian ones? For population biologist Peter Turchin, the answer is that stratified cultures are ideally suited to being conquerors. They come with chains of command. Both empirical and theoretical work suggest that in addition, in unstable environments, stratified societies are better able to survive resource shortages than egalitarian cultures by sequestering mortality to the lower classes. In other words, when times are tough, the unequal access to wealth becomes the unequal distribution of misery and death.