Human bonding in the context of Sexual behaviour

Sexual intercourse (also coitus or copulation) is a sexual activity typically involving the insertion of the erect male penis inside the female vagina and followed by thrusting motions for sexual pleasure, reproduction, or both. This is also known as vaginal intercourse or vaginal sex. Sexual penetration is an instinctive form of sexual behaviour and psychology among humans. Other forms of penetrative sexual intercourse include anal sex (penetration of the anus by the penis), oral sex (penetration of the mouth by the penis or oral penetration of the female genitalia), fingering (sexual penetration by the fingers) and penetration by use of a dildo (especially a strap-on dildo), and vibrators. These activities involve physical intimacy between two or more people and are usually used among humans solely for physical or emotional pleasure. They can contribute to human bonding.

There are different views on what constitutes sexual intercourse or other sexual activity, which can impact views of sexual health. Although sexual intercourse, particularly the term coitus, generally denotes penile–vaginal penetration and the possibility of creating offspring, it also commonly denotes penetrative oral sex and penile–anal sex, especially the latter. It usually encompasses sexual penetration, while non-penetrative sex has been labeled outercourse, but non-penetrative sex may also be considered sexual intercourse. Sex, often a shorthand for sexual intercourse, can mean any form of sexual activity. Because people can be at risk of contracting sexually transmitted infections during these activities, safer sex practices are recommended by health professionals to reduce transmission risk.

Homophily (from Ancient Greek ὁμός (homós) 'same, common' and φιλία (philía) 'friendship, love') is a concept in sociology describing the tendency of individuals to associate and bond with similar others, as in the proverb "birds of a feather flock together". The presence of homophily has been discovered in a vast array of network studies: over 100 studies have observed homophily in some form or another, and they establish that similarity is associated with connection. The categories on which homophily occurs include age, gender, class, and organizational role.

The opposite of homophily is heterophily or intermingling. Individuals in homophilic relationships share common characteristics (beliefs, values, education, etc.) that make communication and relationship formation easier. Homophily between mated pairs in animals has been extensively studied in the field of evolutionary biology, where it is known as assortative mating. Homophily between mated pairs is common within natural animal mating populations.

A sibling is a relative that shares at least one parent with the other person. A male sibling is a brother, and a female sibling is a sister. A person with no siblings is an only child.

While some circumstances can cause siblings to be raised separately (such as foster care or adoption), most societies have siblings grow up together. This causes the development of strong emotional bonds, with siblinghood considered a unique type of relationship. The emotional bond between siblings is often complicated and is influenced by factors such as parental treatment, birth order, personality, and personal experiences outside the family.

Human sexual activity, human sexual practice or human sexual behaviour is the manner in which humans experience and express their sexuality. People engage in a variety of sexual acts, ranging from activities done alone (e.g., masturbation) to acts with another person (e.g., sexual intercourse, non-penetrative sex, oral sex, etc.) or persons (e.g., orgy) in varying patterns of frequency, for a wide variety of reasons. Sexual activity usually results in sexual arousal and physiological changes in the aroused person, some of which are pronounced while others are more subtle. Sexual activity may also include conduct and activities which are intended to arouse the sexual interest of another or enhance the sex life of another, such as strategies to find or attract partners (courtship and display behaviour), or personal interactions between individuals (for instance, foreplay or BDSM). Sexual activity may follow sexual arousal.

Human sexual activity has sociological, cognitive, emotional, behavioural and biological aspects. It involves personal bonding, sharing emotions, the physiology of the reproductive system, sex drive, sexual intercourse, and sexual behaviour in all its forms.

Grief is the response to the loss of something deemed important, in particular the death of a person or animal to which a bond or affection was formed. Although conventionally focused on the emotional response to loss, grief also has physical, cognitive, behavioral, social, cultural, spiritual, political and philosophical dimensions. While the terms are often used interchangeably, bereavement refers to the state of loss, while grief is the reaction to that loss.

The grief associated with death is familiar to most people, but individuals grieve in connection with a variety of losses throughout their lives, such as unemployment, ill health or the end of a relationship. Loss can be categorized as either physical or abstract; physical loss is related to something that the individual can touch or measure, such as losing a spouse through death, while other types of loss are more abstract, possibly relating to aspects of a person's social interactions.

Dame Valerie Jane Morris Goodall (/ˈɡʊdˌɔːl/; née Morris-Goodall; 3 April 1934 – 1 October 2025) was an English primatologist and anthropologist. Regarded as a pioneer in primate ethology, and described by many publications as "the world's preeminent chimpanzee expert", she was best known for more than six decades of field research on the social and family life of wild chimpanzees in the Kasakela chimpanzee community at Gombe Stream National Park in Tanzania. Beginning in 1960, under the mentorship of the palaeontologist Louis Leakey, Goodall's research demonstrated that chimpanzees share many key traits with humans, such as using tools, having complex emotions, forming lasting social bonds, engaging in organised warfare, and passing on knowledge across generations, which redefined the traditional view that humans are uniquely different from other animals.

In 1965 Goodall was awarded a PhD in ethology from the University of Cambridge. In the 1960s Goodall published several accounts of her research in Tanzania, including a series of articles in National Geographic. Her first book-length study, In the Shadow of Man (1971), was later translated into 48 languages. She founded the Jane Goodall Institute in 1977 to promote wildlife conservation, followed by the Roots & Shoots youth programme in 1991, which grew into a global network. Goodall also established wildlife sanctuaries and reforestation projects in Africa and campaigned for the ethical treatment of animals in animal testing, animal husbandry and captivity. Goodall was appointed a United Nations Messenger of Peace in 2002, and advised organisations such as Save the Chimps and the Society for the Protection of Underground Networks.

Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. Present in animals since early stages of evolution, in humans it plays roles in behavior that include social bonding, love, reproduction, childbirth, and the period after childbirth. Oxytocin is released into the bloodstream as a hormone in response to sexual activity and during childbirth. It is also available in pharmaceutical form. In either form, oxytocin stimulates uterine contractions to speed up the process of childbirth.

In its natural form, it also plays a role in maternal bonding and milk production. Production and secretion of oxytocin is controlled by a positive feedback mechanism, where its initial release stimulates production and release of further oxytocin. For example, when oxytocin is released during a contraction of the uterus at the start of childbirth, this stimulates production and release of more oxytocin and an increase in the intensity and frequency of contractions. This process compounds in intensity and frequency and continues until the triggering activity ceases. A similar process takes place during lactation and during sexual activity.