Gender and sexuality are complex and highly variable aspects of culture. Examining evidence from primates and humans as well as the archaeological record, anthropologists have concluded that humans are highly variable, capable of many expressions of gender and sexuality. Cultural anthropologists describe how notions of femininity and masculinity are embedded in institutions and performed by people in their everyday practices. A growing area of research considers the experiences of intersex persons as well as efforts by parents and doctors to assign gender in ambiguous situations. Many cultures allow for greater flexibility beyond the dichotomy of male and female, providing alternative forms of masculinity and femininity for people who wish to transition out of their assigned categories. The study of gender and sexuality also shows how power operates among the categories of gender, particularly through forms of gender ideology such as patriarchy. Like gender, human sexuality is a highly flexible aspect of culture, expressed in a broad range of practices and institutions. Anthropologists have discovered that same-sex practices are quite common even in heteronormative contexts. Recent anthropological research illustrates how gender ideologies shape the identities and experiences of people in communities practicing different forms of sexuality.