For decades, researchers have argued about whether corn was a dietary staple in the late Archaic. The answer, it turns out, was hidden in the turf, tools and toilets of 13 archaeological sites along the coast of Peru. Of 126 soil samples dating back to the late Archaic, 48 percent contained maize pollen. Of 14 stone tools found at one site, 79 percent still carried traces of maize. And finally, scientists analyzed 62 human and canine coprolites, or fossilized feces. Maize was the dominant starch, present in 69 percent of the ancient samples.

　　Some of the evidence is literally crap, but the conclusion isn’t: a corny dietary staple helped drive the growth of civilization in the late Archaic.