IOWA CITY — Hunters and gatherers used stone tools to craft weapons, and hunted and fished at Edgewater Park in Coralville as they passed down the Iowa River 3,800 years ago.The site near the present day Iowa River Landing also revealed evidence of early domestication of plants, a step toward farming, a trio of University of Iowa researchers wrote.“While the occupants did not grow crops, they were changing the way they produced food, shifting toward plants that would later be domesticated, a necessary step toward becoming farmers,” wrote Bill Whittaker, Mary De La Garza and Lynn Alex in “The Archaeological Guide to Iowa,” an offering this year from the University of Iowa Press.