The image of the ultrathin woman with large breasts has come to stand for beauty, sexiness, and success as a woman. In the United States, many people, including many women, define women's breasts primarily as sex objects, as a focus of eroticism. The nutritional, immunological, and emotional benefits of breastfeeding are well documented, and a number of breastfeeding promotion programs have been established. Humans, like all primates, belong to D. M. Ben Shaul's Group II category: mammals who remain in continuous contact with their offspring, such that the offspring can nurse "on demand," whenever they want. Western culture is obsessed with the sexual nature of women's breasts and their role in attracting and keeping male attention, as well as their role in providing sexual pleasure for men and women. The Western preoccupation with breasts as sexual organs spills over into anthropological theory as well, where it is reflected in many anthropologists' recreations of early hominid behavioral evolution.