Human sexuality is the capacity to have erotic experiences and responses. A person's sexual orientation may influence their sexual interest and attraction for another person. Sexuality may be experienced and expressed in a variety of ways, including through thoughts, fantasies, desires, beliefs, attitudes, values, behaviors, practices, roles and relationships, which may manifest by way of biological, physical, emotional, or spiritual aspects. The biological and physical aspects of sexuality largely concern the reproductive functions of the sexes (including the human sexual response cycle), and the basic biological drive that exists in all species. Physical, as well as emotional, aspects of sexuality also include the bond that exists between individuals, and is expressed through profound feelings or physical manifestations of emotions of love, trust, and caring. Spiritual aspects of sexuality concern an individual's spiritual connection with others. Sexuality additionally impacts and is impacted by cultural, political, legal, and philosophical aspects of life. It can refer to issues of morality, ethics, religion and theology.Sexual activity is a vital principle of human living that connects the desire, energy and pleasure of the body to a knowledge of human intimacy, for the sake of erotic love, intimate friendship, human mating and procreation. Interest in sexual activity typically increases when an individual reaches puberty. Some researchers assume that sexual orientation or sexual behavior is determined by genetics; some argue that it is molded by the environment; and others argue that both interact to form sexual orientation. This pertains to the nature versus nurture debate, in which one assumes the features of a person innately correspond to their natural inheritance, as in the case of drives and instincts, or in which one assumes the features of a person continue to change throughout their development and nurturing, as in the case of ego ideals and formative identifications. Contrary to popular opinion, genes are studied not on the premise that they stand for a trait but rather on the premise that only a difference in alleles corresponds to a variation in traits among persons. In the case of human sexuality, this means that "ten percent of the population has chromosomal variations that do not fit neatly into the XX-female and XY-male set of categories."Evolutionary perspectives on human coupling and reproduction – derived, for instance, from studies of phenomena such as reproduction strategies – and social learning theory provide further views of sexuality. Socio-cultural aspects of sexuality include historical developments and religious beliefs, including Jewish views on sexual pleasure within the marriage and certain Christian or other religious views on avoidance of sexual pleasures. Some cultures have been described as sexually repressive. The study of sexuality also includes human identity within social groups, sexually transmitted infections (STIs/STDs) and birth control methods.