Human male sexuality encompasses a wide variety of feelings, behaviors, and physiological processes related to the sexual interests and functioning of human males. It is a complex interplay of biological, psychological, and sociocultural factors. Men's feelings of sexual attraction may be influenced by various physical and social traits of potential partners, and their sexual behavior can be affected by evolved predispositions, individual personality, upbringing, and culture.
Sexual Attraction
Research indicates that men tend to be attracted to young women with bodily symmetry. Facial symmetry, femininity, and averageness are linked with attractiveness. Men typically find female breasts attractive across a variety of cultures. Women with a relatively low waist-to-hip ratio (WHR) are considered more attractive; in Western cultures, a WHR of approximately 0.70 is preferred. Other physical factors include full lips, facial femininity, long hair, low body mass index, and low waist circumference. Preference for slim or plump body builds is culturally variable: in cultures where food is scarce, plumpness is associated with higher status and is more attractive, while the reverse is true in wealthy cultures. Men generally prefer their wives to be younger than they are, though the degree varies between cultures. When choosing long-term partners, both men and women desire partners who are intelligent, kind, understanding, and healthy, and show a preference for similar values, attitudes, personality, and religious beliefs.
Sexual Behavior
Many factors influence men's sexual behavior, including evolved tendencies, upbringing, personality, and relationship status. Compared to women, men on average express a greater interest in casual sex, a greater desire for a variety of sex partners, a higher sex drive, and more frequent sexual fantasies involving variety. Factors that influence the age of first sexual intercourse among youth include family structure, socioeconomic background, academic performance, religiosity, and parental expectations. Males in committed relationships tend to have a restricted sociosexual orientation, being less willing to have sex outside of their relationship. Paternity certainty—the extent to which a male knows or believes a woman's child is his—influences male sexual jealousy, particularly in polygamous societies.
Sexual Orientation
While most men are heterosexual (attracted to women), there are significant minorities of homosexual men (attracted to men) and varying degrees of bisexual men. In Western surveys, approximately 93% of men identify as completely heterosexual, 4% as mostly heterosexual, 0.5% as more evenly bisexual, 0.5% as mostly homosexual, and 2% as completely homosexual. The World Health Organization estimates a worldwide prevalence of men who have sex with men between 3% and 16%. Evidence supports nonsocial (biological) causes of sexual orientation more strongly than social ones, especially for males. This includes moderate genetic influences found in twin studies, evidence for prenatal hormonal effects on brain organization, the fraternal birth order effect, and cross-cultural evidence showing that tolerant cultures do not have significantly higher rates of homosexuality.
Biological and Physiological Aspects
The male reproductive system includes external structures (penis, scrotum) and internal organs (testes, epididymis, vas deferens, seminal vesicles, prostate gland, bulbourethral glands). Testosterone, produced primarily in the testes, is the principal androgen regulating male libido and sexual motivation. The male sexual response cycle consists of four phases: excitement, plateau, orgasm, and resolution. Erection is a neurovascular response mediated by the parasympathetic nervous system, involving nitric oxide release and increased blood flow to the corpora cavernosa. Ejaculation involves rhythmic contractions of pelvic floor muscles propelling semen through the urethra.
Sexual Dysfunction
Common male sexual disorders include erectile dysfunction (inability to initiate or maintain an erection), ejaculation disorders (premature ejaculation, delayed ejaculation, retrograde ejaculation), and hypoactive sexual desire disorder. Causes can be physical (hormonal imbalance, diabetes, cardiovascular disease) or psychological (stress, anxiety, depression).
