Few studies exist of allomaternal nursing in humans. It is relatively common among some cultures, such as the Aka and Efé hunter-gatherers of the Congo Basin, but it does not occur in other foragers such as the !Kung and Hadza of Southern and East Africa. This paper utilizes focal follow observations of Aka and Efé infants, interviews with Aka mothers, ethnographic reports from researchers working with hunter-gatherers, and a survey of the eHRAF cultures to try to answer the following questions: how often does allomaternal nursing occur, who provides it, and under what contexts does it take place? The study indicates that it occurs in many cultures (93% of cultures with data) but that it is normative in relatively few cultures; biological kin, especially grandmothers, frequently provide allomaternal nursing and that infant age, mother's condition, and culture (e.g., cultural models about if and when women other than the mother can nurse an infant or colostrum taboos) impact the nature and frequency of allomaternal nursing. The empirical results of this exploratory study are discussed in the context of existing hypotheses used to explain allomaternal nursing.Anthropologists have conducted several studies of breastfeeding from a variety of perspectives (Fouts, Hewlett, and Lamb 2012;Gottlieb 2004;Sellen 2007) and have occasionally described allomaternal nursing, that is, women other than mother nursing infants, but quantitative studies on the topic do not exist. Nutritional and health benefits of breast-feeding for mothers and infants are well documented (see American Academy of Pediatrics [2005] and Field [2005] for reviews), but what about infants who are breast-fed by women other than mother? Lactation is energetically costly, and allomaternal nursing may increase pathogen transmission between mothers and other infants. La Leche League, a global organization that promotes and assists women with breast-feeding, discourages both wet nursing (nursing another woman's infant, often for pay) and cross-nursing (the occasional nursing of another woman's infant while the mother continues to nurse her own child, often in a child-care situation), because the other women may transmit infectious diseases to the infant or cause the infant to be psychologically confused (Lawrence and Lawrence 2011;Minami 1995). Exceptions exist if the mother has health or other issues that lead to breast-feeding difficulties. 1 Allomaternal nursing occurs in many cultures. Our review of cultures in the electronic Human Relations Area Files (eHRAF), a digital database of 258 cultures from around the world, found that it existed in 97 of 104 cultures with ethnographic data about Barry S. Hewlett is a Professor in the Department of Anthropology of Washington State University, Vancouver (Vancouver, Washington 98686, U.S.A. [hewlett@vancouver.wsu.edu]). Steve Winn is Senior Vice President at the Behavioral Health Network (417 Liberty Street, Springfield, Massachusetts 01104, U.S.A.). This paper was submitted 8 VI 11, accepted 18 I 13, and ele...
