English: Scientific research conducted on non-primate mammals (rodents, canines, felines ...) show that the general neuroanatomical organization of mammals is specifically designed for heterosexual copulation

By simplifying, we can schematize the main phases of reproductive behavior. 1) Odors and especially pheromones make it possible to exchange sexual signals between potential partners. 2) Olfactory circuits (red arrows) make it possible in particular to recognize the partner of the opposite sex and to trigger sexual arousal, which induces vaginal lubrication, erection and copulation. 3) When the male mounts the female, the male's tactile stimuli on female's rump trigger the lordosis behavior reflex. 4) The lordosis circuits (orange arrows) cause the ventral arching of the spine, which elevates the hips and present properly the vagina to the male, thereby facilitating penetration by the penis. 5) The tactile contact between the penis and the genital area triggers the reflex movements of the male's pelvis (pelvic thrusts), then intromission. After intromission, the penis' movements in the vagina trigger the reflex of ejaculation. 6) Tactile stimulation of the clitoris (and the penis for the male) during copulation are transmitted to the brain (blue arrows). 7) Activation of the reward system induces learning which optimize the copulation, particularly by the development of sexual motivation. Moreover, olfactive, auditive and visual signals perceived during the copulation may by conditioning become sexual signals, which optimizes the innate pheromonal signals. There is thus, in the innate neurobiological organization of the organism, a true heterosexual reproductive behavior in nonprimates mammals.

Diagram adapted from: Agmo A. Functional and dysfunctional sexual behavior. Elsevier, 2007 --- Cibrian-Llanderal T., Tecamachaltzi-Silvaran M., Triana-Del R.R., Pfaus J.G., Manzo J., Coria-Avila G.A. Clitoral stimulation modulates appetitive sexual behavior and facilitates reproduction in rats. Physiology & Behavior, 100(2):148-153, 2010 --- Gonzalez-Flores O., Beyer C., Lima-Hernandez F.J., Gomora-Arrati P., Gomez-Camarillo M.A., Hoffman K., Etgen A.M. Facilitation of estrous behavior by vaginal cervical stimulation in female rats involves alpha1-adrenergic receptor activation of the nitric oxide pathway. Behavioural Brain Research, 176(2):237-243, 2007. --- Haga S., Hattori T., Sato T., Sato K., Matsuda S., Kobayakawa R., Sakano H., Yoshihara Y., Kikusui T., Touhara K. The male mouse pheromone ESP1 enhances female sexual receptive behaviour through a specific vomeronasal receptor. Nature, 466(7302):118-122, 2010. --- Kow L.M., Florea C., Schwanzel-Fukuda M., Devidze N., Kami K.H., Lee A., Zhou J., Maclaughlin D., Donahoe P., Pfaff D. Development of a sexually differentiated behavior [lordosis] and its underlying CNS arousal functions. Curr. Top. Dev. Biol., 79:37-59, 2007. --- Knobil E., Neill J.D. (Eds). The physiology of reproduction. Academic Press, 3nd edition, 2005. --- Moncho-Bogani J., Lanuza E., Hernandez A., Novejarque A., Martinez-Garcia F. Attractive properties of sexual pheromones in mice: innate or learned? Physiology & Behavior, 77(1):167-176, 2002 --- Stowers L., Holy T.E., Meister M., Dulac C., Koentges G. Loss of sex discrimination and male-male aggression in mice deficient for TRP2. Science, 295(5559):1493-1500, 2002 --- Wunsch S. Comprendre les origines de la sexualité humaine. Neurosciences, éthologie, anthropologie. L'Esprit du Temps, 2014.

Image: Vector_diagram_of_laboratory_mouse_(black_and_white) – from Gwilz