Iva annua var. macrocarpa: Extinct American Cultigen? 1

Exceptionally large sumpweed achenes have been recovered from archaeological sites in the region extending from Kansas City and the Ozarks to eastern Kentucky and western North Carolina. Dates of occupation range from early first millennium B.C. to the first half of the second millennium A.D. Achene size progressed from slightly larger than modern achenes at the earliest sites to double the modern length at later sites. This is taken as evidence of evolution under domestication.