In the case of humans, long-term partnership is more important than immediate sexual reproduction.Humans, bonobos and dolphins show cooperative behaviour.Using Latex condoms or oral dams reduce the chance that a few types of diseases will be passed on, but it not entirely effective for all STIs.Birth control (like "the Pill") can prevent pregnancy, but won't prevent sexual infections.One reason for this may be that sex partners of these species form strong emotional bonds.

Most animals only mate when the female is at the point of estrus, which is the most fertile period of time in its reproductive cycle. Forcing someone to have sex who does not want to, called rape, is a serious crime in many countries.It involves a man and woman having sex without birth control until the man ejaculates, or releases, semen from his penis into the woman's vagina.The semen, containing sperm (which is made in his testicles), moves to the Fallopian tubes, and if it finds an ovum on its way, it will try to fertilize it. Certain species of animals also have sex for other purposes than to bear offspring.A different word to describe a woman who only likes to have sex with other women is "lesbian".Some people like both men and women, which is called being bisexual.In humans, sexual intercourse seems to serve three types of purposes,which do not exclude one another: In the late 20th century, very effective forms of contraception (birth control) were developed allowing a man and women to help prevent a baby from being made when they have sex. This is a piece of rubber that covers the penis that a man can wear during intercourse, which stops the man's semen from going into the woman's vagina.This does not always work though because the condom may rip or tear.In many cases, this behaviour has shown better results than what an individual can achieve alone.In these animals, the use of sex has evolved beyond reproduction and has taken additional social functions.It is recommended that a couple who have a sexual relationship use two forms of contraception. Contraception allows people to keep "sex for fun" separate from "sex to make children".For example, a fertile couple may use contraception to experience sexual pleasure (recreational).Humans sometimes engage in behaviors that do not include the penetration of sexual organs, such as oral intercourse or anal intercourse or by non-sexual organs (fingering, fisting).These behaviors are sometimes included in the definition of sexual intercourse.Sex reinforces intimate social bonds between individuals.Overall, such cooperation also benefits each member of the group in that they are better able to survive.