Determining an Individual’s Biological Sex

Abstract

Abstract In some situations, it is advantageous to the parent to produce either male or female offspring. Because males can potentially father more offspring than females, high-quality males may have greater reproductive success than high-quality females. For this reason, females in good condition might favour male offspring. While there is good evidence that sex-ratio manipulation occurs in some species, there is little evidence for it in others. Part of a parent’s ability to influence the sex ratio of their progeny probably depends on how sex is determined. We often think of genes controlling whether an individual becomes male or female, which is the case in many species, including mammals. However, sex can also be determined by the environment in which the organism develops. While temperature is the most frequently studied environmental factor, location, population density, and other factors may also contribute to sex determination. Hermaphrodites can change sex from male to female, female to male, or even harbour the reproductive organs of males and females simultaneously. This ability is advantageous when reproductive performance is related to size or when individuals of the opposite sex are difficult to find.