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This volume presents the intricate ways in which sperm compete to fertilize eggs and how this has prompted reinterpretations of breeding behavior from a biological perspective. Sperm Competition in Humans: Classic and Contemporary Readings provides a theoretical framework for the study of sperm competition and also discusses the roles of females and the relationships between paternal care in sperm competition. The chapters focus on everything from evolutionary biology to taxonomic development.
Sperm Competition in Humans by Todd K. Shackelford,Nicholas Pound Pdf
In species with internal fertilization, sperm competition occurs when the sperm of two or more males simultaneously occupy the reproductive tract of a female and compete to fertilize an egg (Parker, 1970). A large body of empirical research has demonstrated that, as predicted by sperm competition theory, males and females in many species possess anatomical, behavioral, and physiological adaptations that have evolved to deal with the adaptive challenges associated with sperm competition. Moreover, in recent years, evolutionary biologists and psychologists have begun to examine the extent to which sperm competition may have been an important selective pressure during human evolution. Some research has suggested that male humans, like males of many bird, insect, and rodent species, might be able to adjust the number of sperm they inseminate according to the risk of sperm competition. Other research has examined whether such responses might be accompanied by psychological changes that motivate human males to pursue copulations when the risk of sperm competition is high. Furthermore, there is research suggesting that aspects of human penile anatomy might function to enhance success in sperm competition. Much of this work has been controversial; some of the findings have been disputed and others have been greeted with skepticism. However, the idea that some aspects of human psychology and behavior might best be understood as adaptations to sperm competition remains intriguing and, in certain cases, very persuasive.
Human Sperm Competition by R.R. Baker,M.A. Bellis Pdf
Behavioural ecologists and evolutionary biologists have long been interested in the biological implications of sperm from different males competing for fertilization of the egg in the female tract. This book discusses these implications for human sexual behaviour and human infertility problems.
The Oxford Handbook of Sexual Conflict in Humans by Todd K. Shackelford,Aaron T. Goetz Pdf
Sexual conflict -- what happens when the reproductive interests of males and females diverge -- occurs in all sexually reproducing species, including humans. The Oxford Handbook of Sexual Conflict in Humans is the first volume to assemble the latest theoretical and empirical work on sexual conflict in humans from the leading scholars in the fields of evolutionary psychology and anthropology. Following an introductory section that outlines theory and research on sexual conflict in humans and non-humans, ensuing sections discuss human sexual conflict and its manifestations before and during mating. Chapters in these sections address a range of factors topics and factors, including: - Sexual coercion, jealousy, and partner violence and killing - The ovulatory cycle, female orgasm, and sperm competition - Chemical warfare between ejaculates and female reproductive tracts Chapters in the next section address issues of sexual conflict after the birth of a child. These chapters address sexual conflict as a function of the local sex ratio, men's functional (if unconscious) concern with paternal resemblance to a child, men's reluctance to pay child support, and mate expulsion as a tactic to end a relationship. The handbook's concluding section includes a chapter that considers the impact of sexual conflict on a grander scale, notably on cultural, political, and religious systems. Addressing sexual conflict at its molecular and macroscopic levels, The Oxford Handbook of Sexual Conflict in Humans is a fascinating resource for the study of intersexual behavior.
This classic work on the rules of sex -- updated for a new generation -- is still as provocative as the day it was published, providing simple explanations for any and all questions about what happens in the bedroom. Sex isn't as complicated as we make it. In Sperm Wars, evolutionary biologist Robin Baker argues that every question about human sexuality can be explained by one simple thing: sperm warfare. In the interest of promoting competition between sperm to fertilize the same egg, evolution has built men to conquer and monopolize women while women are built to seek the best genetic input on offer from potential sexual partners. Baker reveals, through a series of provocative fictional scene, the far-reaching implications of sperm competition. 10% of children are not fathered by their "fathers;" over 99% of a man's sperm exists simply to fight off all other men's sperm; and a woman is far more likely to conceive through a casual fling than through sex with her regular partner. From infidelity, to homosexuality, to the female orgasm, Sperm Wars turns on every light in the bedroom. Now with new material reflecting the latest research on sperm warfare, this milestone of popular science will still surprise, entertain, and even shock.
Since the 1970s, behavioural ecologists and evolutionary biologists have been fascinated by the biological implications of sperm from different males competing for fertilization of the egg in the female reproductive tract. But until Human Sperm Competition there had never been a discussion of the phenomenon for the human species in book form, despite its relevance for a full understanding of human reproduction.The book is a pioneering analysis of the evolutionary biology of human sexuality, proposing that all aspects have been shaped by the phenomenon of sperm competition. Written 20 years ago in 1993-94, the print edition was published in 1995. Despite its age that book's contents are as relevant now as they were two decades ago. Perhaps even more so, because since Baker and Bellis' demonstration that human sperm competition could actually be studied in a variety of ways a number of research groups have taken up the challenge where they left off. Most of these groups have obtained results that build firmly upon Baker and Bellis' original work. A few others created important dialogues. None though have destroyed any crucial part of the foundation first laid down in that 1995 book. But the main way in which Human Sperm Competition remains relevant to this day is that for various reasons - some cultural, some procedural, and yet others due to sheer opportunity - Baker and Bellis were able to do a number of experiments that others since have not had the opportunity to repeat. And the results of those unique experiments were presented in Human Sperm Competition and nowhere else.In the first half of the book the authors explore the role of sperm competition in the evolution of human sexual characteristics, considering for example the architecture of the female reproductive tract, the reasons for male and female infidelity and the possible biological reasons for homosexuality, masturbation and orgasm.In the second half, the mechanism of sperm competition is evaluated in detail, together with the evidence for and the implications of the authors' own Kamikaze Sperm Hypothesis. Human Sperm Competition sets out the thesis that adopting an evolutionary approach to human reproduction exposes the subtle and sophisticated ways in which human sexual anatomy, physiology and behaviour are designed to interact. As a species, understanding this sexual legacy helps explain how we reproduce today and why problems with fertility arise.Over the years, Human Sperm Competition has become a classic in the study of human sexual biology - but although the original hardback is still in print rising costs plus perhaps its classic status have priced it beyond those students who might most wish to read its contents. This digital edition of the original 1995 publication, but at a student-friendly price, now solves this problem.
Sperm Competition and Sexual Selection by Tim R. Birkhead,Anders Pape Møller Pdf
Sperm Competition and Sexual Selection presents the intricate ways in which sperm compete to fertilize eggs and how this has prompted reinterpretations of breeding behavior. This book provides a theoretical framework for the study of sperm competition, which is a central part of sexual selection. It also discusses the roles of females and the relationships between paternal care in sperm competition. The chapters focusing on taxonomic development are diverse and cover all the major animal groups, both vertebrate and invertebrate, and plants. The final chapter provides an overview discussing the relationship between sperm competition and sexual selection in terms of both function and mechanism and how these translate into species fitness. This book will be of prime interest to behaviorists, ecologists and evolutionary biologists, suggesting new avenues of research and new ways of approaching old problems. The only up-to-date summary of a central and popular subject Well known editors and authors Provides a theoretical framework for the study of sperm competition Covers all major animal groups Includes a chapter on plants
Sperm Competition and Its Evolutionary Consequences in the Insects by Leigh W. Simmons Pdf
One hundred years after Darwin considered how sexual selection shapes the behavioral and morphological characteristics of males for acquiring mates, Parker realized that sexual selection continues after mating through sperm competition. Because females often mate with multiple males before producing offspring, selection favors adaptations that allow males to preempt sperm from previous males and to prevent their own sperm from preemption by future males. Since the 1970s, this area of research has seen exponential growth, and biologists now recognize sperm competition as an evolutionary force that drives such adaptations as mate guarding, genital morphology, and ejaculate chemistry across all animal taxa. The insects have been critical to this research, and they still offer the greatest potential to reveal fully the evolutionary consequences of sperm competition. This book analyzes and extends thirty years of theoretical and empirical work on insect sperm competition. It considers both male and female interests in sperm utilization and the sexual conflict that can arise when these differ. It covers the mechanics of sperm transfer and utilization, morphology, physiology, and behavior. Sperm competition is shown to have dramatic effects on adaptation in the context of reproduction as well as far-reaching ramifications on life-history evolution and speciation. Written by a top researcher in the field, this comprehensive, up-to-date review of the evolutionary causes and consequences of sperm competition in the insects will prove an invaluable reference for students and established researchers in behavioral ecology and evolutionary biology.
Sperm Biology by Tim R. Birkhead,Dave J. Hosken,Scott S. Pitnick Pdf
Sperm Biology represents the first analysis of the evolutionary significance of sperm phenotypes and derived sperm traits and the possible selection pressures responsible for sperm-egg coevolution. An understanding of sperm evolution is fast developing and promises to shed light on many topics from basic reproductive biology to the evolutionary process itself as well as the sperm proteome, the sperm genome and the quantitative genetics of sperm. The Editors have identified 15 topics of current interest and biological significance to cover all aspects of this bizarre, fascinating and important subject. It comprises the most comprehensive and up-to-date review of the evolution of sperm and pointers for future research, written by experts in both sperm biology and evolutionary biology. The combination of evolution and sperm is a potent mix, and this is the definitive account. The first review survey of this emerging field Written by experts from a broad array of disciplines from the physiological and biomedical to the ecological and evolutionary Sheds light on the intricacies of reproduction and the coevolution of sperm, egg and reproductive behavior
Sexual Coercion in Primates and Humans by Martin N. Muller,Richard W. Wrangham Pdf
This book presents extensive field research and analysis to evaluate sexual coercion in a range of species—including all of the great apes and humans—and to clarify its role in shaping social relationships among males, among females, and between the sexes.
A growing body of evidence has begun to reveal flaws in the traditional assumption of female passivity and lack of discrimination after copulation has begun. William Eberhard has compiled an impressive array of research on the ability of females to shape the outcome of mating. He describes studies of many different cryptic mechanisms by which a female can accept a male for copulation but nevertheless reject him as a father. Evidence from various fields indicates that such selectivity by females may be the norm rather than the exception. Because most post-copulatory competition between males for paternity is played out within the bodies of females, female behavior, morphology, and physiology probably often influence male success in these contests. Eberhard draws examples from a diversity of organisms, ranging from ctenophores to scorpions, nematodes to frogs, and crickets to humans. Cryptic female choice establishes a new bridge between sexual selection theory and reproductive physiology, in particular the physiological effects of male seminal products on female reproductive processes, such as sperm transport, oviposition, and remating. Eberhard interweaves his review of previous studies with speculation on the consequences of this theoretical development, and indicates promising new directions for future research.
Female Infidelity and Paternal Uncertainty by Steven M. Platek,Todd K. Shackelford Pdf
Although commonly believed that males are more promiscuous than females, new research has revealed that female infidelity is a common occurrence throughout the animal kingdom. Female Infidelity and Paternal Uncertainty is the first book to address how males deal with the consequences of female infidelity and the strategies they have evolved to try to avoid the possibility of raising an offspring they unknowingly did not sire. Each chapter deals with a specific evolved strategy developed to aid males in either limiting opportunities for their mate to be unfaithful or to 'correct' the by-products of infidelity should it occur. With sections including mate guarding, intra-vaginal tactics and paternity assessment, this book will appeal to researchers and graduate students in behavioral biology, evolutionary psychology, human sexuality, anthropology, sociology, reproductive health and medicine.
The 10th-anniversary edition of the book that radical re-evaluates the origins and nature of human sexuality. Since Darwin’s day, we’ve been told that sexual monogamy comes naturally to our species. Mainstream science — as well as religious and cultural institutions — has maintained that men and women evolved in families in which a man’s possessions and protection were exchanged for a woman’s fertility and fidelity. In this groundbreaking book, however, Christopher Ryan and Cacilda Jethá argue that human beings evolved in egalitarian groups that shared food, child care, and, often, sexual partners. Weaving together evidence from anthropology, archaeology, primatology, anatomy, and psychosexuality, the authors show how far from human nature monogamy really is. With intelligence and humour, Ryan and Jethá explain how our promiscuous past haunts our contemporary struggles. They explore why many people find long-term fidelity so difficult; why sexual passion tends to fade even as love deepens; why homosexuality persists in the face of standard evolutionary logic; and what the human body reveals about the prehistoric origins of modern sexuality. Shocking, enlightening, and ultimately inspiring, Sex at Dawn offers a revolutionary understanding of why we live and love as we do.
The Evolution of Sexuality by Todd K. Shackelford,Ranald D. Hansen Pdf
Attraction, mating, reproduction: it is a given that as a species, human beings are concerned with sex. And whether the study compares sexual behaviors of men and women or considers the proportions between nature and nurture, most roads lead back to our distant ancestors and/or our fellow animals. The Evolution of Sexuality collects stimulating new empirical findings and theoretical concepts regarding both familiar themes and emerging areas of interest. Following earlier titles in this series, an interdisciplinary panel of contributors examines topics specific to the whys of male and female sex-related behavior, here ranging from biological bases for male same-sex attraction to the seemingly elusive purpose of the female orgasm. This vantage point between biology and psychology gives readers profound insights not just into human differences and similarities, but also why they continue to matter despite our vast understanding of culture and socialization. And intriguing dispatches from the humanities review sexual themes in classic works of literature and explore the role of parent-offspring conflict in the English Revolution of the seventeenth century. Among the topics covered: Sexual conflict and evolutionary psychology: toward a unified framework. Assortative mating, caste, and class. The functional design and phylogeny of female sexuality. Is oral sex a form of mate retention behavior? Two behavioral hypotheses for the evolution or male homosexuality in humans. Sperm competition and the evolution of human sexuality. The Evolution of Sexuality will attract evolutionary scientists across a variety of disciplines. Faculty, graduate and undergraduate students, and researchers interested in sexuality will find it a springboard for discussion, debate, and further study.