"We know that the first farmers were shorter, they were more prone to disease than the hunter-gatherers," says Samuel Bowles, the director of the Behavioral Sciences Program at the Santa Fe Institute in New Mexico, describing recent archaeological research.

Bowles' own work has found that the earliest farmers expended way more calories in growing food than they did in hunting and gathering it. "When you add it all up, it was not a bargain," says Bowles.

So why farm? Bowles lays out his theory in a new study in the journal Proceedings of the National Academy of Sciences. The reasons are complex, but they revolve around the concept of private property.

Think of these early farmers as prehistoric suburbanites of sorts. The first farmers emerged in less than a dozen spots in Asia and South America. Bowles says they were already living in small villages. They owned their houses and other objects, like jewelry, boats and a range of tools, including fishing gear.