""Proven to work"? Human beings have been around on this planet for many millenia; all the hunting and gathering societies that existed over the past 100,000 years "worked" just fine (otherwise we'd never be here!)."
But whatever the quality of hunter-gathering life, it does not seem to have been capable of creating the surplus needed to expand the world population beyond 4 million.
For the planet as a whole productive capacity has tended to rise, due to agriculture, fossil fuels and fertilisers. "These advances increased the human carrying capacity of the planet", writes Lester Brown, from 4 million 10 000 years ago, to six billion today (State of the Planet, 1999).
To go back to a hunter-gathering society now, you would have to identify which 394 million of the six billion were to be killed, like Pol Pot did when he pushed the Cambodians out of Phnom Phen into the countryside.