In zoology, copulation is animal sexual behavior in which a male introduces sperm into the female's body, especially directly into her reproductive tract. This is an aspect of mating. Many animals that live in water use external fertilization, whereas internal fertilization may have developed from a need to maintain gametes in a liquid medium in the Late Ordovician epoch. Internal fertilization with many vertebrates (such as reptiles, some fish, and most birds) occurs via cloacal copulation, known as cloacal kiss (see also hemipenis), while mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.
In non-primate mammals (rodents, canines, felines, bovines, and equines), the anatomy of the reproductive organs and some circuits of the nervous system are specifically organized for heterosexual copulation. On the other hand, human sexual intercourse stems from a change in biological factors that controls the copulation of mammals, and is mainly learned.
In spiders and insectsEdit
Spiders are often confused with insects, but they are not insects; instead, they are arachnids. Spiders have separate male and female sexes. Before mating and copulation, the male spider spins a small web and ejaculates on to it. He then stores the sperm in reservoirs on his large pedipalps, from which he transfers sperm to the female's genitals. The females can store sperm indefinitely.
For primitive insects, the male deposits spermatozoa on the substrate, sometimes stored within a special structure; courtship involves inducing the female to take up the sperm package into her genital opening, but there is no actual copulation. In groups that have reproduction similar to spiders, such as dragonflies, males extrude sperm into secondary copulatory structures removed from their genital opening, which are then used to inseminate the female. In dragonflies, it is a set of modified sternites on the second abdominal segment. In advanced groups of insects, the male uses its aedeagus, a structure formed from the terminal segments of the abdomen, to deposit sperm directly (though sometimes in a capsule called a spermatophore) into the female's reproductive tract.
This section may be too long and excessively detailed.
Some scientific studies show that the general neuroanatomic organization of non-primate mammals is specifically designed for heterosexual copulation. Serge Wunsch says that, by simplifying, there are three major hardwired neurobiological circuits, controlled by hormones: A) The olfactory circuits (red arrows, diagram below), which underlie sexual arousal and sexual orientation; B) The circuits of sexual reflexes (lordosis, erection, ejaculation ... orange arrows), which allow copulation; C) The circuits of sexual rewards (reward system associated with penis / clitoris - blue arrows), which are involved in sexual learning (especially sexual motivation).
By simplifying, the female cannot have any other sexual activity than lordosis.
In the male, the realization of copulation is more complex, because some learning is necessary, but the innate processes (retrocontrol of penis intromission in the vagina, rhythmic movement of the pelvis, detection of female pheromones) are specific to copulation. These innate processes direct learning heterosexual copulation. Through the coordination of hormones, pheromones and sexual reflexes, there is true reproductive behavior in non-primate mammals.
Evolution of copulation control in hominidsEdit
- Female lordosis behaviour became secondary in hominidae and is non-functional in humans.
- Pheromones become secondary. 90% of sex pheromone receptor genes become pseudogenes, and the vomeronasal organ is altered.
- Sexual activities gradually became dissociated from the hormonal cycles, especially in pan paniscus and humans.
- Sexual learning, induced by sexual rewards and the reward system, became a major factor in hominids.
- The major development of the cortex in hominids led to the gradual emergence of complex cognitive abilities, which have enabled the human species to develop culture.
Vaginal coitus is still practiced in humans, but it is no longer a reflex motor activity, guided by pheromones and controlled by hormones. It is rather an erotic activity, among others, carried out voluntarily to obtain cerebral reward (sexual pleasure).
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