Sperm Competition in Humans

Sperm Competition in Humans

Author: Todd K. Shackelford

Publisher: Springer

Published: 2010-10-29

Total Pages: 0

ISBN-13: 9781441939173

DOWNLOAD EBOOK

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

Human Sperm Competition

Author: R.R. Baker

Publisher: Springer

Published: 1994-12-31

Total Pages: 354

ISBN-13: 0412454300

DOWNLOAD EBOOK

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

The Oxford Handbook of Sexual Conflict in Humans

Author: Todd K. Shackelford

Publisher: Oxford University Press

Published: 2012-01-04

Total Pages: 368

ISBN-13: 0199908303

DOWNLOAD EBOOK

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.


Sperm Wars

Sperm Wars

Author: Robin Baker

Publisher: Basic Books

Published: 2006-01-03

Total Pages: 401

ISBN-13: 0465012965

DOWNLOAD EBOOK

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.


Promiscuity

Promiscuity

Author: Tim Birkhead

Publisher: Harvard University Press

Published: 2000

Total Pages: 300

ISBN-13: 9780674006669

DOWNLOAD EBOOK

Birkhead reveals a world in which males and females vie with each other as they strive to maximize their reproductive success. Color illustrations.


The Evolution of Insect Mating Systems

The Evolution of Insect Mating Systems

Author: David M. Shuker

Publisher:

Published: 2014

Total Pages: 355

ISBN-13: 0199678022

DOWNLOAD EBOOK

Insects display a staggering diversity of mating and social behaviours. Studying these systems provides insights into a wide range of evolutionary and behavioural questions, such as the evolution of sex, sexual selection, sexual conflict, and parental care. This edited volume provides an authoritative update of the landmark book in the field, The Evolution of Insect Mating Systems (Thornhill and Alcock, 1983), which had such a huge impact in shaping adaptationist approaches to the study of animal behaviour and influencing the study of the evolution of reproductive behaviour far beyond the taxonomic remit of insects. This accessible new volume brings the empirical and conceptual scope of the original book fully up to date, incorporating the wealth of new knowledge and research of the last 30 years. It explores the evolution of complex forms of sex determination in insects, and the role of sexual selection in shaping the evolution of mating systems. Selection arising via male contest competition and female choice (both before and after copulation) are discussed, as are the roles of parasites and pathogens in mediating the strength of sexual selection, and the role that parental care plays in successful reproduction. The Evolution of Insect Mating Systems is suitable for both graduate students and researchers interested in insect mating systems or behaviour from an evolutionary, genetical, physiological, or ecological perspective. Due to its interdisciplinary and concept-driven approach, it will also be of relevance and use to a broad audience of evolutionary biologists.


Female Infidelity and Paternal Uncertainty

Female Infidelity and Paternal Uncertainty

Author: Steven M. Platek

Publisher: Cambridge University Press

Published: 2006-08-03

Total Pages: 234

ISBN-13: 1139458043

DOWNLOAD EBOOK

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.


Sperm Biology

Sperm Biology

Author: Scott S. Pitnick

Publisher: Academic Press

Published: 2008-11-21

Total Pages: 683

ISBN-13: 0080919871

DOWNLOAD EBOOK

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


Sex at Dawn

Sex at Dawn

Author: Christopher Ryan

Publisher: Harper Collins

Published: 2010-06-29

Total Pages: 420

ISBN-13: 0062002937

DOWNLOAD EBOOK

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. But this narrative is collapsing. Fewer and fewer couples are getting married, and divorce rates keep climbing as adultery and flagging libido drag down even seemingly solid marriages. How can reality be reconciled with the accepted narrative? It can't be, according to renegade thinkers Christopher Ryan and Cacilda Jethå. While debunking almost everything we "know" about sex, they offer a bold alternative explanation in this provocative and brilliant book. Ryan and Jethå's central contention is that human beings evolved in egalitarian groups that shared food, child care, and, often, sexual partners. Weaving together convergent, frequently overlooked evidence from anthropology, archaeology, primatology, anatomy, and psychosexuality, the authors show how far from human nature monogamy really is. Human beings everywhere and in every era have confronted the same familiar, intimate situations in surprisingly different ways. The authors expose the ancient roots of human sexuality while pointing toward a more optimistic future illuminated by our innate capacities for love, cooperation, and generosity. With intelligence, humor, and wonder, Ryan and Jethå show how our promiscuous past haunts our struggles over monogamy, sexual orientation, and family dynamics. They explore why long-term fidelity can be so difficult for so many; why sexual passion tends to fade even as love deepens; why many middle-aged men risk everything for transient affairs with younger women; why homosexuality persists in the face of standard evolutionary logic; and what the human body reveals about the prehistoric origins of modern sexuality. In the tradition of the best historical and scientific writing, Sex at Dawn unapologetically upends unwarranted assumptions and unfounded conclusions while offering a revolutionary understanding of why we live and love as we do.


Female Control

Female Control

Author: William G. Eberhard

Publisher: Princeton University Press

Published: 1996

Total Pages: 532

ISBN-13: 9780691010854

DOWNLOAD EBOOK

Evidence from various fields indicates that such selectivity by females may be the norm rather than the exception. Because most postcopulatory competition among 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.