Weaning of human children is a complex process involving the introduction of non-breast-milk foods, reduction in suckling activity, and eventual termination of breast feeding. Because the choice of strategies for each component of the weaning process depends on the operating environmental constraints, reproductive demands on women, and prevailing levels of infant and weanling mortality, it is appropriate to examine weaning practices as human adaptive strategies. Here, I examine the structure of weaning and maternal attitudes toward weaning among nomadic Turkana pastoralists from the perspective of human adaptation. Using retrospective and prospective data on breast feeding, the use of non-breast-milk foods, and the cessation of breast feeding, I identify ideal strategies as those defined by Turkana women. Real behavior in relation to weaning, however, deviates considerably from the ideal, and this deviation reflects adaptive responses to nutritional and disease risks to infants. Particular attention is given to problematic aspects of weaning practices in Turkana, such as premature introduction of non-breast-milk foods and abrupt termination of breast feeding, which have been shown to contribute to high infant and weanling mortality in populations in developing countries. These practices have evolved from the dual caretaking and childbearing role of women and the necessity of reconciling the needs of the breast-feeding child with the demands of the next pregnancy. As such, they represent rational strategies for enhancing reproductive success in this and other similarly stressful environments.Members of the Turkana households with whom I worked were extraordinarily cooperative and hospitable, and I am much in their debt. Turkana women, in particular, accepted my presence most graciously and my questions with great patience and humor. Many thanks are extended to members of my field research team, particularly to Lopeyon, Joyce Erupe, and Mohammed Bashir. Rada Dyson- Hudson, Trevor Dixon, and Peg Fry were very helpful in their suggestions regarding solutions to logistical and methodological problems. This research was funded by the National Science Foundation through grant BNS-8718477
