Abstract Females of many species mate with multiple males in a breeding season. One explanation for this behavior is that it facilitates mate choice after copulation. Female choice that occurs after copulation is detectable because not all the female's mates have equal paternity; it is called cryptic female choice because the process is hidden. For example, females may transport sperm from particular males to storage sites near where fertilization occurs, which could result in paternity biased towards those males. Cryptic female choice can have profound effects on the strength and direction of sexual selection, the evolution of mating systems, and the coevolution of female and male reproductive traits that leads to speciation. However, the cryptic nature of postcopulatory female choice has made it extremely difficult to document.
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Human sperm competition - Wikipedia
Researchers have suggested that males produce more and higher quality sperm after spending time apart from their partners, implying that males are responding to an increased risk of sperm competition,  although this view has been challenged in recent years. It is also possible that males may be producing larger volumes of sperm in response to actions from their partners, or it may be that males who produce larger volumes of sperm may be more likely to spend more time away from their partners. By weight, the relative penis size of human males is similar to that of chimpanzees, although the overall length of the human penis is the largest among primates. Copulatory behaviors[ edit ] Human males have several physiological adaptations that have evolved in response to pressures from sperm competition, such as the size and shape of the penis. For example, males who are at a higher risk of sperm competition defined as having female partners with high reproductive value, such as being younger and physically attractive engaged more frequently in semen-displacing behaviors during sexual intercourse than men who were at a lower risk of sperm competition.
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When It Comes To Sperm Competition, Size Can Matter—It's The Female Who Holds The Aces
R and R Test subjects were lab-reared descendants of wild-caught fish. We included Atlantic mollies from the coastal lagoons around the Central Mexican city of Tampico belonging to the subspecies P. Recent phylogenetic analyses argue in favor of full species status of the two subspecies We further included a locally adapted and genetically differentiated i.
Syracuse University Summary: When it comes to mating and determining whose sperm reaches the elusive egg, females control both the playing field and the rules of the game, according to a new study on male sperm competition vs. FULL STORY When it comes to mating and determining whose sperm reaches the elusive egg, females control both the playing field and the rules of the game, according to a new study on male sperm competition vs. Miller, a postdoctoral research associate at SU.