The modern hunter-gatherer goes prowling for food. Okay if you managed to hunt up some money prior to seeking out your food. If not, head down to the soup kitchen or the food bank.
Point is, everything is an ecosystem.
Then thousand years ago was when humans began to engage in systematic agriculture. Instead of hunting and gathering food from wild sources, humans began to domesticate animals and plant crops. What changed minds was discovery of many hunter-gatherer tribes in remote corners of the world. Answer is, nobody did voluntarily. The evidence is that people knew how to cultivate crops and domesticate animals long before they actually did it.