What is responsible for the differences between the sexes in so many animals, from the brilliant plumage of birds of paradise to the antlers on deer? And why are the traits that distinguish the sexes sometimes apparently detrimental to survival? Even when they look more or less alike, why do males and females sometimes behave differently? Questions like these have intrigued scientists and the public alike for many years, and new discoveries are showing us both how wildly variable the natural world is, and how some basic principles can help explain much of that variation. Like natural selection, sexual selection is a process that results from differential representation of genes in successive generations. Under sexual selection, however, the crucial characteristics that determine whether an individual reproduces depend on sexual competition, rather than survival ability. This Very Short Introduction considers the history of our understanding of sexual selection, from Darwin's key insights to the modern day. Considering the investment animals place on reproduction, variation in mating systems, sexual conflict, and the origin of sexual dimorphism, Marlene Zuk and Leigh Simmons discuss questions such as whether females can really choose between males on aesthetic grounds, and how sexual conflict is resolved in different species. They conclude with a consideration of the thorny question of how, and even if, sexual selection theory applies to humans. ABOUT THE SERIES: The Very Short Introductions series from Oxford University Press contains hundreds of titles in almost every subject area. These pocket-sized books are the perfect way to get ahead in a new subject quickly. Our expert authors combine facts, analysis, perspective, new ideas, and enthusiasm to make interesting and challenging topics highly readable. 1. Darwin's Other Big Idea 2. Choosing from the field of competitors 3. Sex roles and stereotypes 4. Sexual selection after mating 5. Sexual conflict 6. Mating systems, or who goes with whom, and for how long 7. How Sex Makes Species Survive Further Reading Index Marlene Zuk is a Professor in the Department of Ecology, Evolution, and Behavior at the University of Minnesota Twin Cities. She has researched into sexual selection for 25 years and in addition to authoring many scholarly articles has written four books for general readers, including Sexual Selections: What We Can and Can't Learn About Sex from Animals (2002, University of California Press) and Sex on Six Legs: Lessons on Life, Love and Language from the Insect World (a New York Times "Editor's Choice"). Her work has appeared in a wide variety of science magazines as well as the Wall Street Journal and other general outlets. Leigh W Simmons is professor in the School of Animal Biology at the University of Western Australia, and Director of the UWA Centre for Evolutionary Biology. She has worked for nearly 40 years on sexual selection, primarily in insects, but also in frogs and mammals, including humans. Leigh is the author of Sperm Competition (2001, Princeton University Press); and co-wrote Ecology and Evolution of Dung Beetles (2011, Wiley-Blackwell), with T. James Ridsdill-Smith; and The Evolution of Insect Mating Systems (2014, Oxford University Press), with David M Shuker.