Homininae, also called "African hominids" or "African apes", is a subfamily of Hominidae. It includes two tribes, with their extant as well as extinct species: 1) the tribe Hominini ―and 2) the tribe Gorillini (gorillas). Alternatively, the genus Pan is sometimes considered to belong to its own third tribe, Panini. Homininae comprises all hominids that arose after orangutans split from the line of great apes. The Homininae cladogram has three main branches, which lead to gorillas, and to humans and chimpanzees via the tribe Hominini and subtribes Hominina and Panina. There are two living species of Panina and two living species of gorillas, but only one extant human species. Traces of extinct Homo species, including Homo floresiensis have been found with dates as recent as 40,000 years ago. Organisms in this subfamily are described as hominine or hominines.
Sexual attraction is attraction on the basis of sexual desire or the quality of arousing such interest. Sexual attractiveness or sex appeal is an individual's ability to attract other people sexually, and is a factor in sexual selection or mate choice. The attraction can be to the physical or other qualities or traits of a person, or to such qualities in the context where they appear. The attraction may be to a person's aesthetics, movements, voice, or smell, among other things. The attraction may be enhanced by a person's adornments, clothing, perfume or hair style. It can be influenced by individual genetic, psychological, or cultural factors, or to other, more amorphous qualities. Sexual attraction is also a response to another person that depends on a combination of the person possessing the traits and on the criteria of the person who is attracted.
Production of milk (lactation) from a male mammal's mammary glands is well-documented in the dayak fruit bat and the Bismarck masked flying fox. The term "male lactation" is not used in human medicine. It has been used in popular literature, such as Louise Erdrich's The Antelope Wife, to describe the phenomenon of male galactorrhea, which is a human condition unrelated to childbirth or nursing. Newborn babies of both sexes can occasionally produce milk. This is called neonatal milk and not considered male lactation.
Concealed ovulation or hidden estrus in a species is the lack of any perceptible change in an adult female when she is fertile and near ovulation. Some examples of perceptible changes are swelling and redness of the genitalia in baboons and bonobos, and pheromone release in the feline family. In contrast, the females of humans and a few other species that undergo hidden estrus have few external signs of fecundity, making it difficult for a mate to consciously deduce, by means of external signs only, whether or not a female is near ovulation.
Sociobiological theories of rape explore how evolutionary adaptation influences the psychology of rapists. Such theories are highly controversial, as traditional theories typically do not consider rape a behavioral adaptation. Some object to such theories on ethical, religious, political, or scientific grounds. Others argue correct knowledge of rape causes is necessary for effective preventive measures.
Sex differences in psychology are differences in the mental functions and behaviors of the sexes and are due to a complex interplay of biological, developmental, and cultural factors. Differences have been found in a variety of fields such as mental health, cognitive abilities, personality, emotion, sexuality, friendship, and tendency towards aggression. Such variation may be innate, learned, or both. Modern research attempts to distinguish between these causes and to analyze any ethical concerns raised. Since behavior is a result of interactions between nature and nurture, researchers are interested in investigating how biology and environment interact to produce such differences, although this is often not possible.
Reproductive success is an individual's production of offspring per breeding event or lifetime. This is not limited by the number of offspring produced by one individual, but also the reproductive success of these offspring themselves.
Parental investment, in evolutionary biology and evolutionary psychology, is any parental expenditure that benefits offspring. Parental investment may be performed by both males and females, females alone or males alone. Care can be provided at any stage of the offspring's life, from pre-natal to post-natal.
Cooperative breeding is a social system characterized by alloparental care: offspring receive care not only from their parents, but also from additional group members, often called helpers. Cooperative breeding encompasses a wide variety of group structures, from a breeding pair with helpers that are offspring from a previous season, to groups with multiple breeding males and females (polygynandry) and helpers that are the adult offspring of some but not all of the breeders in the group, to groups in which helpers sometimes achieve co-breeding status by producing their own offspring as part of the group's brood. Cooperative breeding occurs across taxonomic groups including birds, mammals, fish, and insects.
Sexual division of labour (SDL) is the delegation of different tasks between the male and female members of a species. Among human hunter-gatherer societies, males and females are responsible for the acquisition of different types of foods and shared them with each other for a mutual or familial benefit. In some species, males and females eat slightly different foods, while in other species, males and females will routinely share food; but only in humans are these two attributes combined. The few remaining hunter-gatherer populations in the world serve as evolutionary models that can help explain the origin of the sexual division of labour. Many studies on the sexual division of labour have been conducted on hunter-gatherer populations, such as the Hadza, a hunter-gatherer population of Tanzania. In modern day society, sex differences in occupation is seen across cultures, with the tendency that men do technical work and women tend to do work related to care.
Sex at Dawn: The Prehistoric Origins of Modern Sexuality is a 2010 book about the evolution of human mating systems by Christopher Ryan and Cacilda Jethá. In opposition to what the authors see as the "standard narrative" of human sexual evolution, they contend that having multiple sexual partners was common and accepted in the environment of evolutionary adaptedness. The authors contend that mobile, self-contained groups of hunter-gatherers were the norm for humans before agriculture led to high population density. Before agriculture, according to the authors, sex was relatively promiscuous and paternity was not a concern. This dynamic is similar to the mating system of bonobos. According to the book, sexual interactions strengthened the bond of trust in the groups. Far from causing jealousy, social equilibrium and reciprocal obligation were strengthened by playful sexual interactions.
Menstruation is the shedding of the uterine lining (endometrium). It occurs on a regular basis in uninseminated sexually reproductive-age females of certain mammal species.
The Evolution of Human Sexuality is a 1979 book about human sexuality by the anthropologist Donald Symons, in which the author discusses topics such as human sexual anatomy, ovulation, orgasm, homosexuality, sexual promiscuity, and rape, attempting to show how evolutionary concepts can be applied to humans. Symons argues that the female orgasm is not an adaptive trait and that women have the capacity for it only because orgasm is adaptive for men, and that differences between the sexual behavior of male and female homosexuals help to show underlying differences between male and female sexuality. In his view, homosexual men tend to be sexually promiscuous because of the tendency of men in general to desire sex with a large number of partners, a tendency that in heterosexual men is usually restrained by women's typical lack of interest in promiscuous sex. Symons also argues that rape can be explained in evolutionary terms and feminist claims that it is not sexually motivated are incorrect.
Sexual swelling, sexual skin, or anogenital tumescence refers to localized engorgement of the anus and vulva region of some female primates that vary in size over the course of the menstrual cycle. Thought to be an honest signal of fertility, male primates are attracted to these swellings; preferring, and competing for, females with the largest swellings.
In evolutionary psychology and behavioral ecology, human mating strategies are a set of behaviors used by individuals to select, attract, and retain mates. Mating strategies overlap with reproductive strategies, which encompass a broader set of behaviors involving the timing of reproduction and the trade-off between quantity and quality of offspring.
Extended female sexuality is where the female of a species mates despite being infertile. In most species, the female only engages in copulation when she is fertile. However, extended sexuality has been documented in Old World primates, pair bonded birds and some insects. Extended sexuality is most prominent in human females who exhibit no change in copulation rate across the ovarian cycle.
Human mate guarding refers to behaviours employed by both males and females with the aim of maintaining reproductive opportunities and sexual access to a mate. It involves discouraging the current mate from abandoning the relationship whilst also warding off intrasexual rivals. It has been observed in many non-human animals, as well as humans. Sexual jealousy is a prime example of mate guarding behaviour. Both males and females use different strategies to retain a mate and there is evidence that suggests resistance to mate guarding also exists.
The ovulatory shift hypothesis holds that women experience evolutionarily adaptive changes in subconscious thoughts and behaviors related to mating during different parts of the ovulatory cycle. It suggests that what women want, in terms of men, changes throughout the menstrual cycle. Two meta-analyses published in 2014 reached opposing conclusions on whether the existing evidence was robust enough to support the prediction that women's mate preferences change across the cycle. A newer 2018 review does not show women changing the type of men they desire at different times in their fertility cycle.
Human reproductive ecology is a subfield in evolutionary biology that is concerned with human reproductive processes and responses to ecological variables. It is based in the natural and social sciences, and is based on theory and models deriving from human and animal biology, evolutionary theory, and ecology. It is associated with fields such as evolutionary anthropology and seeks to explain human reproductive variation and adaptations. The theoretical orientation of reproductive ecology applies the theory of natural selection to reproductive behaviors, and has also been referred to as the evolutionary ecology of human reproduction.
Few animals have a menopause: humans are joined by just four other species in which females live substantially longer than their ability to reproduce. The others are all cetaceans: beluga whales, narwhals, orcas and short-finned pilot whales. There are various theories on the origin and process of the evolution of menopause. These attempt to suggest evolutionary benefits to the human species stemming from the cessation of women's reproductive capability before the end of their natural lifespan. Explanations can be categorized as adaptive and non-adaptive:
