Piperno, Laguna Tuxpan, Iguala Valley (IMAGE) Smithsonian Tropical Research Institute Caption Cores from Laguna Tuxpan in Mexico's Iguala Valley, provided evidence for maize and squash cultivation along its edges by ~8000 B.P. and for the major dry event between 1800 and 900 B.P. Credit Ruth Dickau Usage Restrictions Credit: Ruth Dickau License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.