Sperm competition. Sperm competition is a term used to refer to the competitive process between the sperm of two or more different males to fertilize an egg of a lone female. You will see that sperm competition is further proof, that humans are polygamists. Sperm competition goes back to the beginning of mankind.
Sperm Wars is a popular science book by evolutionary biologist Robin Baker about sperm competition. Through a series of short fictional stories and discussion following them, Baker proposes evolutionary functions for sexual habits, mostly on the principle of competition between sperm of different men for a prized egg. The book is controversial,  both because of its explanations of homosexuality , sexual assault , and prostitution, and because some critics have claimed that several of the hypotheses in the book are not supported by scientific research. The shape of the penis and the thrusting during intercourse serve to remove other men's semen. Baker also proposes that men adjust the amount of sperm they ejaculate based on the time their mate has spent away from them. This literal sperm warfare was not observed in a subsequent experiment,  but Baker criticizes the protocol in this latter experiment. Based on studies with a fiber optic endoscope attached to a man's penis during sex, Baker describes how the cervix behaves during sex and orgasm, dipping down "like an elephant's trunk" into the pool of semen so that the sperm can more easily swim into it, the so-called "upsuck theory" of female orgasm.
Nazi human experimentation was a series of medical experiments on large numbers of prisoners, including children, by Nazi Germany in its concentration camps in the early to mid s, during World War II and the Holocaust. Nazi physicians and their assistants forced prisoners into participating; they did not willingly volunteer and no consent was given for the procedures. Typically, the experiments were conducted without anesthesia and resulted in death, trauma , disfigurement or permanent disability , and as such are considered examples of medical torture. At Auschwitz and other camps, under the direction of Eduard Wirths , selected inmates were subjected to various experiments that were designed to help German military personnel in combat situations, develop new weapons, aid in the recovery of military personnel who had been injured, and to advance the Nazi racial ideology. After the war, these crimes were tried at what became known as the Doctors' Trial , and revulsion at the abuses perpetrated led to the development of the Nuremberg Code of medical ethics.
The testes are the primary male sexual organs in that they make sperm and produce testosterone. The sperm is the male sex cell, or gamete, and each testicle produces more than 4 million new sperm per hour [source: Angier ]. Testosterone is the hormone that causes male secondary sex characteristics such as facial and pubic hair, thickened vocal cords and developed muscles.