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Why did we start farming? What was once thought to be an unknowable question now offers a range of answers, including the possibility that it co-evolved with private property. According to a newstudy, however, farming in modern-day North America began for a rather more mundane reason: There were a lot of mouths to feed.

“Explaining domestication remains one of the most important and contentious research problems in archaeology,” University of Utah anthropologists Elic Weitzel and Brian Codding write in Royal Society Open Science. In an attempt to further debate on the issue, Wentzel and Brian focused on two theories: one, called niche construction, that supposes farming was a natural extension of humans’ efforts to shape their environments; and another, based on behavioral ecology, suggesting that people developed farming as a response to scarce resources.

According to the niche construction hypothesis, Weitzel and Codding argue, the dawn of agriculture should happen during times when population density is low relative to the available resources. The behavioral ecology hypothesis, by contrast, is quite explicit that farming should emerge out of need—that is, when the population is high relative to naturally available resources.

Farming in modern-day North America began for a rather more mundane reason: There were a lot of mouths to feed.

For data, the researchers turned their attention to the Eastern Agricultural Complex, a region comprising archaeological sites in modern-day Kentucky, Arkansas, Missouri, and Illinois, among others, where it’s thought people first started farming roughly 5,000 years ago. Then, the team dated seven sites in the region listed in the Canadian Archaeological Radiocarbon Database, which gathers radiocarbon dates on archaeological sites throughout the United States and Canada. By looking at how the number of sites changed over time, Weitzel and Codding could get at least a rough estimate of how the population changed in the region.

The results? Consistent with the behavioral ecology model, the population in the Eastern Agricultural Complex roughly doubled between 6,400 and 5,500 years ago, just before people in the region began farming.

“Not only were populations at this time higher than ever before, but they had been significantly increasing for approximately 1,000 years, likely placing strong pressure on local resources,” ultimately requiring some kind of organized agricultural, Weitzel and Codding write.

Still, there remain unanswered questions—for one thing, whether the uptick in population was the only factor that led to agriculture, or was just one of many antecedents.