STABLE CARBON AND OXYGEN ISOTOPES IN HUMAN TOOTH ENAMEL - IDENTIFYINGBREAST-FEEDING AND WEANING IN PREHISTORY

This paper investigates the utility of stable carbon and oxygen isotop es in human dental enamel to reveal patterns of breastfeeding and wean ing in prehistory. Enamel preserves a record of childhood diet that ca n be studied in adult skeletons. Comparing different teeth, we used de lta(13)C to document the introduction of solid foods to infant diets a nd delta(18)O to monitor the decline of breastfeeding. We report ename l carbonate delta(13)C and delta(18)O of 33 first molars, 35 premolars , and 25 third molars from 35 burials from Kaminaljuyu, an early state in the valley of Guatemala. The skeletons span from Middle Preclassic through Late Postclassic occupations, ca. 700 B.C. to 1500 A.D. Secti ons of enamel were removed from each tooth spanning from the cusp to t he cemento-enamel junction. Stable isotope ratios were measured on CO2 liberated by reaction of enamel with H3PO4 in an automated carbonate system attached to a VC Optima mass spectrometer. Within a skeleton, t eeth developing at older ages are more enriched in C-13 and more deple ted in O-18 than teeth developing at younger ages. Premolars average 0 .5% higher in delta(13)C than first molars from the same skeleton (P = 0.0001), but third molars are not significantly enriched over premola rs. The shift from first molars to premolars may be due to the shift t o solid foods from lipid-rich milk. After 2 years, when premolars begi n to mineralize, the delta(13)C in, childhood diets did not change sys tematically. First molars and premolars are similar in delta(18)O, but third molars average 0.7% lower than first molars (P = 0.0001) and 0. 5% lower than premolars (P = 0.0003). First molar and premolar delta(1 8)O is heavier, because breast milk is more enriched in O-18 than is d rinking water. Hence, many children continued to nurse during the peri od of premolar formation. Together, these results indicate that Kamina ljuyu children had begun to eat solid maize foods before the age of 2 years but continued to drink breast milk until much later. (C) 1998 Wi ley-Liss, Inc.