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Sexual reproduction is the antithesis of clonality because genes that are faithfully copied during asexual replication are genetically scrambled (recombined) during the sexual processes of meiosis and fertilization. Sex has long been an evolutionary enigma because it appears at face value to entail several fitness costs and risks in the short term whereas its potential benefits would seem to be rather diffuse and postponed. This chapter reviews the diverse explanations for recombinational sex, ranging from the level of molecular genetics to the echelons of short-term ecology and long-term evolution. It thus sets the stage for the book's extended thesis that any attempt to understand the adaptive significance of sex is likely to be facilitated by analyzing clonal systems, and vice versa.

This chapter examines evolutionary branching in sexual populations. As sexual populations converge to what would be a branching point in clonal models, splitting obviously becomes a problem, because mating between different marginal phenotypes generally creates intermediate phenotypes. Through segregation and recombination, sexual reproduction can prevent the establishment of diverging phenotypic clusters in randomly mating populations. To allow for a phenotypic split, mating needs to be assortative with respect to the ecological trait that is under disruptive selection. Thus, the question of evolutionary branching in sexual populations, that is, of adaptive speciation, is intimately tied to questions about the evolution of assortative mating. If evolutionary branching occurs in sexual populations due to the presence of assortative mating mechanisms, the diverging phenotypic clusters will show prezygotic reproductive isolation at least to some extent, and hence they can be viewed as representing incipient species.

At the conclusion of World War II, more than 600,000 men returned to the United States with long-term disabilities, profoundly destabilizing male sexuality in America. This chapter excavates the contours of that change and its attendant anxieties in order to broaden scholarly interpretations of sexuality in the postwar period. Ultimately, the chapter shows that, although sexual reproduction is often coded female and sexual performance male, such a popularly held binary does not hold true when it comes to the history of paraplegic World War II veterans. To these veterans, and to the medical men who treated them, sexual reproduction became the ultimate signifier of remasculinization.

Pathways of social group formation are poorly known for the origin of the eukaryotic cell, sexual reproduction, and many interspecific mutualisms. In the origin of multicellularity and eusociality, social group formation has usually occurred via a subsocial pathway (association of parents and offspring), with a semisocial pathway (association of same-generation organisms) occurring occasionally. The essential genetic condition for social group formation in groups exhibiting altruism is that relatedness should be positive – a prediction overwhelmingly supported by available evidence in the case of both the origin of multicellularity and the origin of eusociality. Non-genetic factors (ecological or synergistic) facilitate social group formation by increasing the benefits of grouping and the costs of living singly. Ecological factors promoting the formation of multicellular organisms and eusocial societies include environmental stresses and predator pressure. A major synergistic factor promoting the formation of multicellular organisms, eusocial societies, and interspecific mutualisms is division of labour.

Whereas numerous infidel women convert to Christianity on the early modern English stage, relatively few infidel men convert. Chapter 5 explores the interplay of race, gender, and salvation in William Shakespeare’s The Merchant of Venice, John Fletcher’s The Island Princess, and Philip Massinger’s The Renegado. The frequency with which Jewish, Turkish, and Moorish women convert to Christianity in English drama more generally responds to the convergence of theological and medical discourses that highlighted the role of male seed in creating a child’s identity, and reflects as well Reformation theology’s linkage of spiritual and sexual reproduction. Nonetheless, anxieties about what an infidel mother might pass on to her children, even when she is married to a Christian man, prompt Fletcher’s and Massinger’s plays to employ the discourse of martyrdom in order to verify the women’s acquisitions of true Christian faith.

Comprised of only about 200 species, the Choanoflagellata is a small phylum that occurs in most aquatic habitats. Choanoflagellates are unicellular, solitary, or colony-forming ‘flagellates’ without chloroplasts, and are either pelagic or sessile. They reproduce by binary fission, and sexual reproduction is implied by the presence of conserved meiotic genes. In addition, choanoflagellates have a complicated life cycle. Their sister-group relationship with metazoans is supported by morphological and molecular evidence.

Sex and genders occupy a central place in the human mind and have a long history of alternative interpretations throughout human cultures. Although intimately linked to reproduction in animals and other multicellular eukaryotes, sex is fundamentally not a reproductive process. This chapter first discusses what sex is and why it evolved, arguing that it is best defined by the presence of meiosis, that it might have originated as a DNA-repair mechanism, and is likely maintained by indirect benefits stemming from recombination.We then present the several kinds of mating categories (mating types, sexes, genders, self-incompatibility systems), discussing their similarities and differences, and the reasons why they exist. We introduce the concepts of sex-ratio selection and sexual selection, which are arguably the main evolutionary forces underlying the dynamics of sex-determination systems. Finally, this chapter we argues against the traditional distinction between sex determination and primary sex differentiation, defining sex determination as the whole process that leads, from undifferentiated gonads or meristems, to the development of differentiated reproductive organs. This broad definition widens the scope of our book, to also include, for example, sex differentiation in simultaneous and sequential hermaphrodites.

This chapter discusses John Milton’s account of prelapsarian existence in Paradise Lost, which implies that the first human sexual reproduction occurred between God and Adam in an act that overwhelmed Adam and produced Eve as a new sexual partner for man. Based on the Lucretian meditation on mixed modes of generation, the first act of sexual reproduction makes a materialist and philosophical contribution to the discussion of Milton’s construction of paradise as a place resistant to but tempted by obsolete and “fallen” forms of categorization.

This chapter outlines key issues in scientific literature concerning how evolutionary processes have shaped the human mind. To that end, psychologists have drawn on Charles Darwin’s sexual selection hypothesis, or how males compete for reproduction and the role of female choice in the process. Darwin argued that evolution hinged on the diversity resulting from sexual reproduction. Evolutionary psychologists posit that heterosexual men and women evolved powerful, highly patterned, and universal desires for particular characteristics in a mate. Critics, however, contend that Darwin’s theory of sexual selection was erroneous, in part because his ideas about sexual identity and gender were influenced by the social mores of his elite Victorian upper class. Despite this critique, some researchers argue similarly to Darwin that love is part of human biological makeup. According to their hypotheses, cooperation is the centerpiece of human daily life and social relations. This makes the emotion of love, both romantic and maternal love, a requirement not just for cooperation, but also for the preservation and perpetuation of the species. That said, researchers speculate that encounters with unfamiliar people, coincident with activated neural mechanisms associated with negative judgments, likely inspire avoidance behavior and contribute to emotional barriers. This suggests the need to further study the social, psychological, and clinical consequences of the link between positive and negative emotions.

A series of major transitions in evolution has generated the biological hierarchy (e.g., genes in cells, cells in organisms, organisms in societies) observed today. Each transition requires that previously selfish, free-living individuals join together to form a group resembling an individual in its own right. This book seeks to identify the principles of social evolution that underlie the major transitions, focusing on the evolution of the eukaryotic cell, sexual reproduction, multicellularity, eusociality, and interspecific mutualisms. It suggests that each major transition has three stages – social group formation, social group maintenance, and social group transformation. Using Hamilton's inclusive fitness theory (kin selection theory) as its conceptual foundation, the book investigates two underexplored issues. First, to what extent do common principles operate at each stage of the major transitions and what is the evidence for their operation; and second, what are the principles underlying social group transformation?

Macroevolutionary patterns concern phylogenies of hosts and their parasites. From those, co-speciation occurs; but host switching is a common evolutionary process and more likely when hosts are close phylogenetically and geographical ranges overlap. Microevolutionary processes refer to allele frequency changes within population. In arms races, traits of hosts and parasites evolve in one direction in response to selection by the other party. With selective sweeps, advantageous alleles rapidly spread in host or parasite population and can become fixed. With antagonistic negative frequency-dependent fluctuations (Red Queen dynamics) genetic polymorphism in populations can be maintained, even through speciation events. A Red Queen co-evolutionary process can favour sexual over asexual reproduction and maintain meiotic recombination despite its other disadvantages (two-fold cost of sex). Local adaptation of host and parasites exist in various combinations; the relative migration rates of the two parties, embedded in a geographical mosaic, are important for this process.

The Homoscleromorpha is a small phylum consisting of roughly sixty extant species of marine ‘sponges’. Previously placed within the Demospongiae, both morphological and molecular studies now indicate that it is a separate phylum. The basal membrane contains collagen IV, which, along with recent molecular studies, supports a sister-group relationship between the homoscleromorphs and the eumetazoans. During sexual reproduction of the homoscleromorphs, spermatogonia develop from choanocytes and whole choanocyte chambers differentiate into spermiocysts. Both homoscleromorphs and eumetazoans possess a large number of cell-signalling and adhesion genes, some of which are absent in Amphimedon.

The chapter outlines different models of nature in medieval Aristotelian and Platonic philosophy in order to show how the Rose plays them against each other to articulate its own model of the complex relationship between art and nature. For the Rose there is no getting at nature except by means of art, as suggested by the self-conscious artificiality of the figure of Nature, taken from the allegories of twelfth-century Neoplatonism. Art, a broad category that encompasses all human activity, is insufficient in describing nature’s truths and is potentially sophistic in its lies. However, questions of nature are always questions of art on whose help humans depend to understand and to represent to themselves a nature that can never be fully known. Finally, the model of reproductive nature is used to legitimate the reproduction of texts and the continuation of arts that is literary production.

The account of hylomorphic structure developed for artifacts is in this chapter extended to organisms. An account is given of the origin of organisms in sexual reproduction that is modeled on the artifactual account but that, of course, lacks the important role of intentional making. It is then argued, drawing on work by Karen Neander and Ruth Millikan, that something similar to what intentional making does in the case of artifacts is accomplished by evolution in the case of organisms. Cases like that of Davidson’s Swampman are not cases of organisms, or hylomorphically complex entities of any kind, at all.

This chapter examines the resilience of arctic biota to climatic fluctuations and disturbance. The ability to repair decimated populations by sexual reproduction or, as in the case with plants, also asexually is all the more astonishing given the climatic and resource limitations of high-latitude habitats. This ability of the arctic biota to recover from near extinction may be attributed to the reduced inter-specific competition that can be enjoyed in the sparseness of the arctic landscapes. The chapter discusses reproduction at high latitudes; human demography in the Arctic; longevity at high latitudes; predator-prey interactions; phenology and reproduction; and plant reproduction.

This chapter explores how cloning reproduces and sustains the centrality of sex in the biopolitics of the zoo. Focusing on the cloned banteng, it considers the so-called “genetic values” that are so central to zoological parks today. In this context, the zoo is envisioned not as a place populated by hundreds of clones, carbon copies of endangered animals living in the wild, but as a place that uses available technologies in order to manage sexual reproduction, and thus sustain a deftly balanced genetic composition within a limited amount of space. The chapter analyzes the context of genetic value vis-à-vis the ways in which selective breeding has historically been constituted to create what Harriet Ritvo has called “genetic capital” in agriculture. It also discusses the biopolitics of genetic values in the case of domestic animals and concludes by examining genetic values in relation to nature and culture, as well as the kinds of wild life and endangered species that are enabled by the genetic values of zoos.

Chapter one describes “The Quandary Over Plant Sex” in its historical context. The sexual role of pollen wasn’t discovered until the late 17^th century, suggesting a deep cultural bias. Beliefs concerning sex in humans, from Galen and Aristotle onward, were influenced by gender ideology. The lower social status of women suggested a one-sex model, whereby female character and physiology were construed as deficient versions of the male. Plants, because of their association with women, came to be regarded as female. Flowers are often emblematic of women in literature, but flowers seem to produce fruits without carnality, by parthenogenesis. In paintings of the Annunciation, the lily appears almost as regularly as the angel Gabriel as a symbol of Mary’s purity. The association of flowers with female purity hindered the discovery of sex in plants. Although most people are aware of pollen, widespread confusion about its role in sexual reproduction still lingers.

In Systema Naturæ (1735, 1758), Carolus Linnaeus proposed a definition of the Kingdom Animalia: natural objects that grow, live, and sense. In contrast, plants grow and live but do not sense, while minerals grow but do not live or sense. In this definition of the animal kingdom, species are arranged in classes, families, and genera. This division of organisms into animals and plants was almost unchallenged for more than 100 years. In 1866, Ernst Haeckel came up with the first classification of living beings based on Charles Darwin’s ideas on evolution. He separated the Kingdom Animalia from the new Kingdom Protista based on the possession of tissues and organs. Today, the animal kingdom is restricted to multicellular animals, that is, the Metazoa. This chapter provides an overview of metazoans, including their apomorphies, sexual reproduction and life cycle, and genes involved in organising the metazoan body. It also describes some of the metazoan morphological characters, including cilia and flagella, choanocytes, cell junctions and epithelia.