Samples taken from pollen records, stone tool residues and fossilized feces suggest the food crop was actively grown, processed and eaten, adding weight to the argument Andean society was agricultural, not maritime-based, they said.
"If you look at the origins of civilizations around the world -- from Egypt to China and India -- they are all based on agriculture," study co-author Jonathan Haas of The Field Museum in Chicago said.
Despite that, he said, many researchers have believed Andean early civilization was different and evolved from exploiting marine resources.
"That theory has now been the dominant theory since the mid-1970s but more data has become available saying that there are not just [coastal] sites but there are some big inland sites too," he told the BBC.
"People started to find corn at the inland sites, and the argument was that the corn was really a condiment and used for ceremonial purposes."
The findings from his team's study "topples that notion" by showing corn, also called maize, and other agricultural crops were widespread at the archaeological study sites, Haas said.
Although marine resources would have been an important source of protein, he said, "finding corn, beans, sweet potato and a number of other things in the diet -- that is an agriculturally-based society."