It's the idea that people living close to nature tend to be noble. It's seeing all those sunsets that does it. You can't watch a sunset and then go off and set fire to your neighbor's tepee. Living close to nature is wonderful for your mental health.
I have no faith in human perfectibility. I think that human exertion will have no appreciable effect upon humanity. Man is now only more active - not more happy - nor more wise, than he was 6000 years ago.