Carbon and nitrogen stable isotopic signatures of human dietary change in the Georgia Bight

Measurement of carbon and nitrogen stable isotope ratios (613C and 615N) in samples of human bone collagen (n = 93) from a temporal series of four prehistoric (early preagricultural, late preagricultural, early agricultural, late agricultural) and two historic (early contact, late contact) periods from the Georgia Bight, a continental embayment on the southeast- ern U.S. Atlantic coast, reveals a general temporal trend for less negative S13C values and less positive 615N values. This trend reflects a concomitant de- crease in emphasis on marine resources and increased reliance on C,-based resources, especially maize. This dietary reorientation is most apparent for the early agricultural sample (AD 1150-1300), coinciding with the Mississip- pian florescence in the eastern United States. There is, however, a shift toward the use of C3 (non-maize) foods during the last prehistoric period (AD 1300-14501, which is likely related to environmental stress and social disrup- tion. A heavier use of maize and terrestrial resources in general after the establishment of mission centers on barrier islands is indicated. A reduced dietary breadth during the mission period may have contributed to the extinc- tion of these populations in the eighteenth century. 6 1992 Wiley-Liss, Inc.