Sex and Gender
Sex and Gender
In this chapter, sex will refer to the central process of meiosis and syngamy in eukaryotic organisms. Although some form of sexuality characterizes the life cycle of many eukaryotic organisms (i.e., virtually all fungi, plants, and animals), not all eukaryotes are sexual (e.g., many protists) (Margulis 1970, 1996; Bell 1982). Certain asexual protists, for example, only undergo mitosis and never alternate between haploid and diploid stages by way of meiosis and syngamy. Consequently, one of the most fundamental questions in biology is: Why do certain organisms go through meiosis and syngamy while others do not? Despite the apparent simplicity of this query, evolutionary biologists have not provided an entirely satisfactory explanation for the evolution of sex. Much of the difficulty arises because there appears to be no single answer. Moreover, sex is often confused with other associated phenomenon. For instance, one completely subordinate, but intimately related, occurrence is the evolution of gender in organisms that go through meiosis and syngamy. In his essay on the evolution of sex, Ghiselin (1988) aptly wrote, “Gender means the differentiation into males, females, and such alternatives as hermaphrodites. It also includes the differences between sperm and eggs. Such differences are important because they create the circumstances that make sex a puzzle” (p. 9). Yet he dismisses this subject in the next sentence: “Otherwise we are not much concerned about gender either.” Here we clarify the relationship between the evolution of sex and the evolution of gender. This is a critical concept to comprehend because gender differences are nearly universal in sexual organisms. We also discuss some of the major hypotheses proposed to explain why sex exists and recent empirical work that sheds light on the factors that may favor meiosis and syngamy, regardless of gender differences. In the remainder of the chapter, we present a more thorough analysis of the evolution of gender, including a discussion of what the fundamental gender difference is and why there are so many different mechanisms that produce more derived gender differences.
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