Sexual dimorphism, i.e., differences in morphology, physiology, and behavior between conspecific males and females, is ubiquitous, extensive, and often species-specific, indicative of its rapidly evolving nature. Ever since Darwin first described a general theory of sexual selection to explain the extraordinary differences between males and females of the same species, biologists have proposed a variety of mechanisms ranging from runaway selection to good genes to sexual conflict. While a popular approach is studying the effects of sexual selection on different components of fitness, the results of these studies are generally difficult to interpret and are typically not generalizable across populations, let alone taxa. Recent advances in the "omics" field are transforming the way that we study patterns and processes involved in sexual selection. At the molecular level, sexual dimorphism is present in gene expression differences between the sexes, providing a powerful framework to study sexual selection. By studying genes that are sex-biased in expression, we will better understand the underlying genetic basis of traits that are sexually dimorphic. Alreadly, studies of sex-biased genes in model organisms, particularly Drosophila, have revealed that male-biased genes are among the most rapidly evolving functional classes of genes. However, while a number of intrinsic factors appear to correlate with evolutionary rate (e.g., gene expression level, codon bias), it is unclear whether any of these factors drive the rapid divergence of male-biased genes. Another important discovery is the prevalence of sex-biased gene expression. However, even with widespread sexual dimorphism at the phenotypic level, it remains unknown the extent to which sex-biased gene expression exists in humans and their primate relatives. In fact, studies of sexual dimorphism on a molecular level in primates have been very few, even though understanding this phenomenon in humans could further our knowledge of the nature of sex-biased phenotypes and diseases. In this thesis, I advance our knowledge of the genetic bases and mechanisms that shape sexual dimorphism. First, I review a classic framework that biologists have traditionally applied to define and partition fitness measures between males and females in the model system, Drosophila. Second, I apply a molecular framework to compare the relative roles of intrinsic factors on the evolutionary rate of rapidly evolving male-biased genes in Drosophila. Third, I review the current state of our knowledge of sexual dimorphism and sex-biased gene expression in humans. Fourth, I present a bioinformatics framework to identify the extent of sex-biased expression in primate tissue and to examine the selective forces involved in their evolution. Overall, I demonstrate the effectiveness of using a functional comparative genomics approach in studying the nature of sexual dimorphism at the molecular level across multiple taxa.

Evolutionary innovations have shaped the diversity of animal and plant forms. The origin of these evolutionary innovations implies the origin of new regulatory pathways, which leads to a change in the development pattern. Most evolutionary innovations as shown by research in a variety of models have suggested that they are caused not by the appearance of new genes, but rather by the acquisition of new function by pre-existing genes. Understanding the genetic and molecular changes which lead to a shift in the developmental pattern leading to the regulation of the particular trait is therefore one of the key challenges of evolutionary developmental genetics. Sex comb in Drosophila is a sexually dimorphic morphological character, which serve as a good model system to understand how genetic modifications have taken place in the course of evolution leading to as an evolutionary innovation. Though genetic network controlling the development of this trait has been studied to some extent in D. melanogaster, and Sophophoran group, understanding of the changes that have lead to the origin of this new character from the primitive bristles remain to be dissected out. In this context the question asked in the present project is "What are the changes in the developmental genetic pathway underlying the evolution of the primitive bristles pattern of Drosophila in general to sex comb as in the Sophophoran group". Studies in the present project explore the differences in the genetic regulators viz, Sex combs reduced, dachshund and bric-a- brac from the species cluster with primitive bristle to species with sex comb of Drosophila.

In very general terms, "scaling" can be defined as the structural and func tional consequences of differences in size (or scale) among organisms of more or less similar design. Interest in certain aspects of body size and scaling in primate biology (e. g. , relative brain size) dates to the turn of the century, and scientific debate and dialogue on numerous aspects of this general subject have continued to be a primary concern of primatologists, physical an thropologists, and other vertebrate biologists up to the present. Indeed, the intensity and scope of such research on primates have grown enormously in the past decade or so. Information continues to accumulate rapidly from many different sources, and the task of synthesizing the available data and theories on any given topic is becoming increasingly formidable. In addition to the formal exchange of new ideas and information among scientific experts in specific areas of scaling research, two of the major goals of this volume are an assessment of our progress toward understanding various size-related phe nomena in primates and the identification of future prospects for continuing advances in this realm. Although the subject matter and specific details of the issues considered in the 20 chapters that follow are very diversified, all topics share the same fundamental and unifying biological theme: body size variation in primates and its implications for behavior and ecology, anatomy and physiology, and evolution.

It's obvious why only men develop prostate cancer and why only women get ovarian cancer. But it is not obvious why women are more likely to recover language ability after a stroke than men or why women are more apt to develop autoimmune diseases such as lupus. Sex differences in health throughout the lifespan have been documented. Exploring the Biological Contributions to Human Health begins to snap the pieces of the puzzle into place so that this knowledge can be used to improve health for both sexes. From behavior and cognition to metabolism and response to chemicals and infectious organisms, this book explores the health impact of sex (being male or female, according to reproductive organs and chromosomes) and gender (one's sense of self as male or female in society). Exploring the Biological Contributions to Human Health discusses basic biochemical differences in the cells of males and females and health variability between the sexes from conception throughout life. The book identifies key research needs and opportunities and addresses barriers to research. Exploring the Biological Contributions to Human Health will be important to health policy makers, basic, applied, and clinical researchers, educators, providers, and journalists-while being very accessible to interested lay readers.

Disproportionate attention has long been paid to males in human and other social systems. The basic structures used to explain social behavior in sociological and biological work have overwhelmingly emphasized the significance and shape of male behavior and far less female behavior which is surely at least as important. Stratification, sexual selection, and natural selection of what women do among themselves and how they relate to men was explored in this volume for the first time. It is now available in a paperback edition, with a new introduction by Lionel Tiger. Do females conduct aggressive encounters with each other? Or do they have no impact on mate selection and hence on the future of the genotype? Is the main negotiation of females with males and not among themselves during this selective process? Do the usually larger size and frequently more elaborate behavioral displays of males betray the fact that the burden of selective functioning falls on males and not on females? It is improbable that the answer to these questions is "yes" and that there is little or nothing happening in all-female groups that affects not only how their communities operate but, more importantly in the long run, the genotype of their species. For those species in which gregarious social behavior is a sine qua non for successful reproduction, what are the principles of selection that operate through females? Are female hierarchies more abrasive or generous than male ones? Do they focus more on reproduction than production? What are the forms of female social grouping that either support, modify, inhibit, or stimulate sexual and hence natural selection? This work goes far beyond the slogans of our time for important responses to basic questions.

Just over one hundred and thirty years ago Charles Darwin, in The Descent of Man and Selection in Relation to Sex (1871), developed remarkably accurate conclusions about man's ancestry, based on a review of general comparative anatomy and psychology in which he regarded sexual selection as a necessary part of the evolutionary process. But the attention of biologists turned to the more general concept of natural selection, in which sexual selection plays a complex role that has been little understood. This volume significantly broadens the scope of modern evolutionary biology by looking at this important and long neglected concept of great importance. In this book, which is the first full discussion of sexual selection since 1871, leading biologists bring modern genetic theory and behavior observation to bear on the subject. The distinguished authors consider many aspects of sexual selection in many species, including man, within the context of contemporary evolutionary theory and research. The result is a remarkably original and well-rounded view of the whole concept that will be invaluable especially to students of evolution and human sexual behavior. The lucid authority of the contributors and the importance of the topic will interest all who share in man's perennial fascination with his own history. The book will be of central importance to a wide variety of professionals, including biologists, anthropologists, and geneticists. It will be an invaluable supplementary text for courses in vertebrate biology, theory of evolution, genetics, and physical anthropology. It is especially important with the emergence of alternative explanations of human development, under the rubric of creationism and doctrines of intelligent design.