The example of the savages who have almost all been found in this state seems to bear out the conclusion that humanity was made to remain in it for ever, that it was the true youth of the world, and that all further progresses have been so many steps, apparently towards the perfection of the individual, and really towards the decrepitude of the species.
He ascribes to metallurgy and agriculture the fatal resolution which brought this Arcadian existence to an end.

Agriculture entailed the origin of property in land.

Moral and social inequality were introduced by the man who first enclosed a piece of land and said, This is mine, and found people simple enough to believe him.

He was the founder of civil society.
The general argument amounts to this: Man's faculty of improving himself is the source of his other faculties, including his sociability, and has been fatal to his happiness.

The circumstances of his primeval life favoured the growth of this faculty, and in making man sociable they made him wicked; they developed the reason of the individual and thereby caused the species to deteriorate.