David M. Buss
Evolutionary psychology, broadly conceived, dates back to Darwin. He offered this scientific vision at the end of his monumental book, On the Origin of Species: “In the distant future I see open fields for more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation” (Darwin, 1859). This Handbook of Evolutionary Psychology (second edition), published 156 years after these prophetic words, symbolizes the emergence of evolutionary psychology based on Darwin's vision.
Evolutionary psychology is still a young scientific field, and there's a long and exciting road ahead. Aspects of the field's conceptual foundations remain legitimate topics of debate, such as the nature and specificity of psychological adaptations and the importance of individual differences. Many phenomena remain unexamined, awaiting new explorers of the human mind equipped with the conceptual tools that evolutionary psychology provides. Many of the conceptual foundations are now in place, offering a solid metatheoretical framework from which to build. Hundreds of psychological and behavioral phenomena have been documented empirically, findings that would never have been discovered without the guiding framework of evolutionary psychology. Evolutionary psychology has proved its worth many times over in its theoretical and empirical harvest. If a viable alternative metatheoretical framework to evolutionary psychology exists for understanding the origins and nature of the human mind, it has not been revealed to the scientific community. The second edition of this Handbook, published a decade after the first, takes stock of where the field is today and where it needs to go.
Until recently, a handbook of this scope would have been impossible. The empirical corpus of research testing evolutionary psychological hypotheses was too slim. Now the body of work has mushroomed at such a rapid rate that I had to make difficult decisions about what to include for this volume to keep it to a reasonable length. Some important areas regrettably could not be covered. Most chapters had to be shortened, sometimes dramatically. The extensity of coverage, however, reveals that evolutionary psychology has penetrated every existing branch of psychology.
Psychologists working in some subdisciplines in times past could safely disregard evolutionary psychology. Now the robustness of evolutionary hypotheses and the rapid accumulation of empirical findings make it impossible to ignore for all but those who remain conceptually insular. Scientists working in cognitive, social, developmental, personality, neuroscience, or clinical psychology, and more recently cultural psychology, cannot afford to close their eyes to the insights offered by evolutionary psychology.
Some view evolutionary psychology as an optional perspective, an explanation of last resort, to be brought in only when all other alternatives have been exhausted. In my view, this position is naïve. Evolutionary psychology represents a true scientific revolution, a profound paradigm shift in the field of psychology. The human mind can no longer be conceived as it has been in mainstream psychology, implicitly or explicitly, as a blank slate onto which parents, teachers, and culture impose their scripts; or as a domain-general learning device; or a set of content-free information processing mechanisms; or as a content-free neural or connectionist network. Instead, the human mind comes factory-equipped with an astonishing array of dedicated developmental programs for psychological mechanisms, designed over deep time by natural and sexual selection, to solve the hundreds of statistically recurring adaptive problems that our ancestors confronted. Understanding these mechanisms of mind requires understanding their evolved functions—what they were designed by selection to accomplish, the adaptive problems that selection favored them to solve, the specific manner in which they contributed to fitness. Just as a medical researcher's insights into the heart, liver, or kidney would be viewed as woefully incomplete without knowledge of their functions, explanations of psychological mechanisms will almost invariably be incomplete without specifying their functions. Evolutionary psychology is no longer a discretionary or elective theoretical option for psychology. It is essential, necessary, and indispensable.
At the current point in the history of psychology, the mainstream field is partitioned into subdisciplines—cognitive, social, personality, developmental, clinical, and hybrid areas such as cognitive neuroscience. Evolutionary psychology provides the metatheoretical foundation that unites the disparate branches of the sprawling field of psychology, and suggests that the human mind cannot be logically parsed in the manner the subdisciplines imply. Consider “stranger anxiety” as a candidate psychological adaptation. Its function is to motivate the infant to recoil from potentially dangerous humans and to maintain close proximity to caregivers, thereby avoiding hazards that strangers might pose. Stranger anxiety possesses a number of well-articulated design features. It shows universality, emerging in infants in all cultures in which it has been studied. It emerges predictably during ontogeny at roughly six months of age, coinciding with the time when infants begin crawling away from their mothers and potentially encountering strangers. And its focus centers on strange males rather than strange female because strange males historically have been more hazardous to infants' health. Stranger anxiety shows all the characteristics of “improbable design” for achieving a specific function.
In which subdiscipline of psychology does stranger anxiety belong? It obviously involves information processing, and so could be claimed by cognitive psychology. It shows a predictable ontogenetic unfolding, so it could be claimed by developmental psychology. It is activated by interactions with others, so clearly it belongs to social psychology. Individual infants differ in the intensity of stranger anxiety, so it falls within the province of personality psychology. The mechanism can malfunction in a minority of infants, so it is relevant to clinical psychology. And its biological substrate must include the brain, so neuroscience can also lay claim. Obviously, stranger anxiety belongs simultaneously to all or to none.
Evolutionary psychology breaks down these traditional disciplinary boundaries and reveals them to lack logical or scientific warrant. Viewed through the theoretical lens of adaptive problems and their evolved psychological solutions, evolutionary psychology offers the only cogent nonarbitrary means for carving the mind at its natural joints. It provides the conceptual unification of the disparate branches of psychology that currently operate in virtual isolation. And it integrates psychology theoretically with the rest of the natural sciences in a unified causal framework.
It is a great honor and privilege to serve as editor for The Handbook of Evolutionary Psychology (second edition), which contains such a high-powered assembly of outstanding scientists. Whereas the first edition of the Handbook contained 34 chapters, this second edition contains 52 chapters (plus essays by Steven Pinker, Donald Symons, and Richard Dawkins), reflecting both the rapidly expanding empirical base of evolutionary psychology and its penetration into new and previously uncharted domains ranging from food to culture to public policy implications. The dramatic expansion of topical coverage includes entirely new chapters on food, the behavioral immune system, inbreeding avoidance, hunter-gatherer parenting and families, prejudice, warfare, cultural evolution, morality, ritual, religion, group selection, leadership, evolutionary genetics, evolutionary endocrinology, evolutionary political psychology, and evolutionary consumer psychology. Its authors are housed in diverse disciplines, including psychology, anthropology, biology, political science, business school, law school, and the humanities.
This Handbook begins with a foreword from Steven Pinker, who provides a powerful narrative of his intellectual journey to evolutionary psychology, and describes his views about why evolutionary psychology is necessary for psychological science. The Handbook ends with an eloquent afterword by evolutionary biologist Richard Dawkins, whose theoretical contributions have informed much work in the discipline. In between are 52 chapters, parsed into nine parts. Each part has its own introduction.
Part One, Foundations of Evolutionary Psychology, contains five chapters that outline the logic of the enterprise, the methods used, and controversial issues surrounding the field. Part Two, Survival, contains five chapters that deal, respectively, with struggles with the physical environment, with other species (predators and prey), and with other humans. Part Three, Mating, begins with an insightful essay by Donald Symons, in which he articulates the logic of adaptationism and offers a novel hypothesis about mate-rejection anxiety. It is followed by eight chapters that range in content from attraction to contest competition, from sexual coercion to love in long-term mating, highlighting the breadth and depth of theory and research in the domain of human mating. Part Four, Parenting and Kinship, contains an excellent introductory essay by Martin Daly, and is followed by chapters on cooperation and conflict among kin, parental investment, parent-offspring conflict, the evolution of the human family, and hormones, and human sociality.
Group living, which all scholars recognize is one of the most crucial contexts in which humans evolved, is so important that it warranted two parts. The first, Part Five, Group Living: Cooperation and Conflict, deals with social exchange, aggression, prejudice, and social exclusion, and ends with a new chapter on leadership in warfare. The second, Part Six: Culture and Coordination, contains seven entirely new chapters. These focus on cultural evolution, morality, status hierarchies, ritual, religion, and group selection. Taken together, these chapters reflect the explosion of theoretical and empirical work on the monumental importance of group living, and the upsurge of interest in understanding previously neglected aspects of group living such as ritual, religion, morality, and culture.
Part Seven, Interfaces With Traditional Psychology Disciplines, contains eight chapters on how the conceptual foundations of the current disciplines within psychology can be informed by an evolutionary framework. Part Eight, Interfaces Across Traditional Academic Disciplines, contains five chapters, four entirely new and one heavily revised. The new chapters focus, respectively, on evolutionary anthropology, evolutionary genetics, evolutionary psychology and endocrinology, and evolutionary political psychology; the revised chapter deals with evolutionary literary study. Collectively, these key chapters reflect the degree to which evolutionary sciences have become centrally integrated with so many far-flung disciplines within the life sciences.
Part Nine, Practical Applications of Evolutionary Psychology, provides the concluding section of the Handbook. Chapters deal with evolutionary approaches to public policy, consumer behavior, organizational leadership, and legal issues.
After a long succession of conceptual advances and empirical discoveries, a robust field of evolutionary psychology has finally emerged. Darwin's prophetic vision is being realized—a psychology based on a new foundation. And beyond psychology, evolutionary approaches to human behavior are penetrating domains Darwin is unlikely to have envisioned, from evolutionary genetics to a deep understanding of human culture. I like to think Charles Darwin would have been both humbled and gratified, and perhaps even awed, by the intellectual flowering forecast by his scientific prophecy.