Libido in the context of "Species preservation"

Marriage, also called matrimony or wedlock, is a culturally and often legally recognised union between people called spouses. It establishes rights and obligations between them, as well as between them and their children (if any), and between them and their in-laws. It is nearly a cultural universal, but the definition of marriage varies between cultures and religions, and over time. Typically, it is an institution in which interpersonal relationships, usually sexual, are acknowledged or sanctioned. In some cultures, marriage is recommended or considered to be compulsory before pursuing sexual activity. A marriage ceremony is called a wedding, while a private marriage is sometimes called an elopement.

Around the world, there has been a general trend towards ensuring equal rights for women and ending discrimination and harassment against couples who are interethnic, interracial, interfaith, interdenominational, interclass, intercommunity, transnational, and same-sex as well as immigrant couples, couples with an immigrant spouse, and other minority couples. Debates persist regarding the legal status of married women, leniency towards violence within marriage, customs such as dowry and bride price, marriageable age, and criminalization of premarital and extramarital sex. Individuals may marry for several reasons, including legal, social, libidinal, emotional, financial, spiritual, cultural, economic, political, religious, sexual, and romantic purposes. In some areas of the world, arranged marriage, forced marriage, polygyny marriage, polyandry marriage, group marriage, coverture marriage, child marriage, cousin marriage, sibling marriage, teenage marriage, avunculate marriage, incestuous marriage, and bestiality marriage are practiced and legally permissible, while others areas outlaw them to protect human rights. Female age at marriage has proven to be a strong indicator for female autonomy and is continuously used by economic history research.

Eroticism (from Ancient Greek ἔρως (érōs) 'love, desire' and -ism) is a quality that causes sexual feelings, as well as a philosophical contemplation concerning the aesthetics of sexual desire, sensuality, and romantic love. That quality may be found in any form of artwork, including painting, sculpture, photography, drama, film, music, or literature. It may also be found in advertising. The term may also refer to a state of sexual arousal or anticipation of such – an insistent sexual impulse, desire, or pattern of thoughts.

As French novelist Honoré de Balzac stated, eroticism is dependent not just upon an individual's sexual morality, but also the culture and time in which an individual resides.

Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a female, the testicles in a male. In response to the signals, the gonads produce hormones that stimulate libido and the growth, function, and transformation of the brain, bones, muscle, blood, skin, hair, breasts, and sex organs. Physical growth—height and weight—accelerates in the first half of puberty and is completed when an adult body has been developed. Before puberty, the external sex organs, known as primary sexual characteristics, are sex characteristics that distinguish males and females. Puberty leads to sexual dimorphism through the development of the secondary sex characteristics, which further distinguish the sexes.

On average, females begin puberty at age 10½ and complete puberty at ages 15–17; males begin at ages 11½–12 and complete puberty at ages 16–17. The major landmark of puberty for females is menarche, the onset of menstruation, which occurs on average around age 12½. For males, first ejaculation, spermarche, occurs on average at age 13. In the 21st century, the average age at which children, especially females, reach specific markers of puberty is lower compared to the 19th century, when it was 15 for females and 17 for males (with age at first periods for females and voice-breaks for males being used as examples). This can be due to any number of factors, including improved nutrition resulting in rapid body growth, increased weight and fat deposition, or exposure to endocrine disruptors such as xenoestrogens, which can at times be due to food consumption or other environmental factors. However, more modern archeological research suggests that the rate of puberty as it occurs now is comparable to other time periods. Growth spurts began at around 10–12, but markers of later stages of puberty such as menarche had delays that correlated with severe environmental conditions such as poverty, poor nutrition, and air pollution. Puberty that starts earlier than usual is known as precocious puberty, and puberty which starts later than usual is known as delayed puberty.

Lust is an intense desire for something. Lust can take any form such as the lust for sexual activity (see libido), money, or power; but it can also take such mundane forms as the lust for food (see gluttony; as distinct from the need for food) or the lust for redolence (when one is lusting for a particular smell that brings back memories). Lust is similar to, but distinguished from, passion, in that properly ordered passion propels individuals to achieve benevolent goals whilst lust does not.

An erection (clinically: penile erection or penile tumescence) is a physiological phenomenon in which the penis becomes firm, engorged, and enlarged. Penile erection is the result of a complex interaction of psychological, neural, vascular, and endocrine factors, and is often associated with sexual arousal, sexual attraction or libido, although erections can also be spontaneous. The shape, angle, and direction of an erection vary considerably between humans.

Physiologically, an erection is required for a male to effect penetration or sexual intercourse and is triggered by the parasympathetic division of the autonomic nervous system, causing the levels of nitric oxide (a vasodilator) to rise in the trabecular arteries and smooth muscle of the penis. The arteries dilate causing the corpora cavernosa of the penis (and to a lesser extent the corpus spongiosum) to fill with blood; simultaneously the ischiocavernosus and bulbospongiosus muscles compress the veins of the corpora cavernosa restricting the egress and circulation of this blood. Erection subsides when parasympathetic activity reduces to baseline.

Chemical castration is castration via anaphrodisiac drugs, whether to reduce libido and sexual activity, to treat cancer, or otherwise. Unlike surgical castration, where the gonads are removed through an incision in the body, chemical castration does not remove organs and is not a form of sterilization.

Chemical castration is generally reversible when treatment is discontinued, although permanent effects in body chemistry can sometimes be seen, as in the case of bone density loss increasing with length of use of depot medroxyprogesterone acetate (DMPA). In men, chemical castration reduces sex drive and the capacity for sexual arousal, side effects of some drugs may include depression, suicidal ideation, hot flashes, anemia, infertility, increase in body fat and higher risks of cardiovascular diseases and osteoporosis. In women, chemical castration acts by decreasing testosterone levels in order to lower their sex drive, side effects include the deflation of breast glands, expansion of the size of the nipple and shrinking of bone mass.

An anaphrodisiac (also antaphrodisiac or antiaphrodisiac) is a substance that quells or blunts the libido. It is the opposite of an aphrodisiac, something that enhances sexual appetite. The word anaphrodisiac comes from the Greek privative prefix ἀν-, denoting negation, and aphrodisiac, from the Greek goddess of love, Aphrodite. Some people use anaphrodisiacs in order to curb a very high libido or due to hypersexuality. However anaphrodisiacs are also used by those with an average libido, at times due to having incessant schedules.