Why was the ancient city of Cahokia abandoned? New clues rule out one theory. Apr 13, 2021 11:00 am by National GeographicIllinois in the News Share on Facebook Tweet Email Images U. of I. archaeologist Caitlin Rankin has likely ruled out the hypothesis that flooding caused by timber overharvesting made the ancient city of Cahokia increasingly uninhabitable. Share on Facebook Tweet Email