Leo Damrosch in Humanities:
Rousseau’s first great work was a Discourse on the Origin and Foundations of Inequality among Men, written in 1749 as an entry in a prize competition (he didn’t win—the judges said his submission was too long). the expected answer in those days would have been that God created us to be unequal, or else that nature did. Either answer would confirm the rightness of social hierarchy and privilege. Rousseau, far more pessimistic than Marx would later be, accepted the truth that inequality is inseparable from human culture, but he wanted to know why. The answer was the idea that would underlie everything Rousseau ever wrote: man is naturally good, but society has made him wicked. That is to say, we are not corrupted by original sin as the churches taught, or driven by instinct to dominate each other as Thomas Hobbes taught. If we are indeed selfish and competitive and possessive, it is because we have been conditioned to be. Rousseau imagined a pre-civilized state of nature in which our ancestors, more like apes than like ourselves, had no need or opportunity to exploit and enslave each other. As hunter-gatherers they could be essentially self-sufficient. The irrevocable change came with the invention of metallurgy and agriculture, twin foundations of a developed civilization. (Interestingly, Jared Diamond says much the same thing in Guns, Germs, and Steel.) Each of these advances has contributed to our material well-being, but they are only possible in an organized society in which the many are controlled by the few. What then develops, accordingly, is bureaucracies, legal systems, and organized religions that teach people to accept their lot in this vale of tears.
More here.