The Handbook of Evolutionary Psychology

1. Evolutionary psychology provides a crucial lens for understanding the mind.

Evolutionary psychology was the organizing framework—the source of “explanatory adequacy” or a “theory of the computation”—that the science of psychology had been missing.

Unifying framework. Evolutionary psychology offers a framework that integrates the disjointed human disciplines into a single, logically consistent research program. It provides a way to understand the human mind and brain by considering the evolutionary forces that shaped them. This approach contrasts with the Standard Social Science Model (SSSM), which assumes the mind is a blank slate, largely shaped by culture and environment.

Moving beyond description. Evolutionary psychology seeks to explain why mental and social phenomena exist, rather than simply describing them. It aims to uncover the evolved functions of psychological mechanisms, providing a deeper understanding of human behavior. This explanatory power is what sets evolutionary psychology apart from traditional approaches.

Transformative potential. By mapping our universal human nature, evolutionary psychology can transform the social sciences into theoretically principled scientific disciplines with genuine predictive and explanatory power. This involves understanding the evolved mechanisms that regulate behavior and the informational inputs that trigger them. This understanding is essential for a more veridical social and behavioral science.

2. Adaptationism is key to understanding organic design.

Adaptationism is based on the recognition that selection is the only known natural physical process that builds highly ordered functional organization (adaptations) into the designs of species.

Selection's role. Natural selection is the only known natural process capable of generating complex, useful, and nonrandom organization in living systems. This organization, known as adaptations, is the result of a history of selection in ancestral environments.

Understanding adaptations. By analyzing the recurrent structure of a species' ancestral world and the selection pressures that operated ancestrally, scientists can predict, discover, map, and understand the functional architecture of organisms. This approach is central to evolutionary psychology.

Beyond fitness teleology. Evolutionary psychology rejects the idea that human behavior is solely driven by fitness maximization. Instead, it focuses on the evolved circuit logic of neural programs, which may or may not correspond to current fitness maximization. This distinction is crucial for understanding the complexities of human behavior.

3. Psychology is reverse engineering.

Psychologists—evolutionary or otherwise—are engineers working in reverse.

Understanding the mind. Psychologists are tasked with reverse-engineering the human neural architecture, dissecting its computational architecture into functionally isolable information processing units (programs), and determining how these units operate, both computationally and physically. This process requires theories of adaptive function.

Distinguishing adaptations. Not all traits of organisms are functional adaptations. Some are by-products of adaptations, while others are simply evolutionary noise. Design evidence, which demonstrates a fit between a system's design and its proposed function, is crucial for identifying adaptations.

The engineering standard. The organic machinery in question must have properties that cause it to solve an adaptive problem precisely, reliably, and economically. If not, then its ability to solve the problem may be incidental, a side effect of a system designed to perform some alternative adaptive function.

4. The EEA is crucial for understanding evolved programs.

The design of each adaptation assumes the presence of certain background conditions and operates as a successful problem solver only when those conditions are met.

Environment of Evolutionary Adaptedness (EEA). The EEA refers to the statistical composite of enduring selection pressures or cause-and-effect relationships that pushed the alleles underlying an adaptation systematically upward in frequency until they became species-typical or reached a frequency-dependent equilibrium.

Adaptations and the past. Psychological programs were shaped by how well they solved adaptive problems among our hunter-gatherer ancestors, not by how well they solve the problems faced by modern humans. Understanding the EEA is essential for understanding the functional architecture of the mind.

Modern environments. When a program operates outside the envelope of ancestral conditions that selected for its design, it may appear to be a poorly engineered problem solver. Being mindful of the EEA concept changes how research is designed and what is discovered.

5. "Innate" is not the opposite of "learned."

Even if a program that causes a particular kind of learning was itself learned, there had to be a prior program that caused that learning to occur, and so on.

The inevitability of nativism. Everyone is a nativist, whether they know it or not. Even extreme advocates of the role of the environment in shaping human behavior make nativist claims about the "innate" structure of the evolved neural machinery that learns or responds to the environment.

Evolved learning programs. Any learned behavior is the joint product of "innate" equipment interacting with environmental inputs and, therefore, cannot be solely attributed to the action of the environment on the organism. Evolved programs—instincts—are not the opposite of learning; they are the engines through which learning takes place.

The importance of programs. The important question for any particular behavior is not, "Is it learned?" but, "What kind of evolved programs produced it?" More specifically, "What is the nature of the universal, species-typical evolved cognitive programs through which the organism learns this particular type of behavior, acquires this kind of knowledge, or produces this form of behavior?"

6. Evolutionary psychology dissolves traditional disciplinary boundaries.

Evolutionary psychology breaks down these traditional disciplinary boundaries and reveals them to lack logical or scientific warrant.

Transcending subdisciplines. Evolutionary psychology reveals that traditional disciplinary boundaries lack logical or scientific warrant. Adaptive problems and their evolved psychological solutions cut across cognitive, social, developmental, personality, neuroscience, and clinical psychology.

A unifying framework. Evolutionary psychology offers the only 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.

Integration with natural sciences. Evolutionary psychology integrates psychology theoretically with the rest of the natural sciences in a unified causal framework. It provides a metatheoretical foundation that unites the disparate branches of the sprawling field of psychology.

7. Music and religion may be byproducts of other adaptations.

Recent books by Pascal Boyer and Scott Atran have insightfully explained the phenomenon of religious belief as a byproduct of adaptations (such as a theory of mind module and free-rider detection mechanisms) that are demonstrably useful for solving other adaptive problems.

Adaptations and byproducts. Not every trait is an adaptation. Some traits are byproducts of adaptations, while others are simply evolutionary noise. It is important to distinguish between these different types of traits when studying the human mind.

Explaining complex phenomena. Evolutionary psychology can explain complex phenomena, such as music and religion, as byproducts of adaptations that evolved to solve other adaptive problems. This approach provides a deeper understanding of these phenomena.

The importance of function. Understanding the evolved function of a psychological mechanism is essential for understanding its design. Just as a medical researcher's insights into the heart, liver, or kidney would be woefully incomplete without knowledge of their functions, explanations of psychological mechanisms will almost invariably be incomplete without specifying their functions.

8. Life history theory integrates with evolutionary psychology.

Life History Theory and Evolutionary Psychology provides a means for uncovering psychological adaptations designed to make important budget allocation trade-offs.

Energy budgets and trade-offs. All energy budgets of an organism are finite, so trade-offs are inevitable. Life history theory (LHT) provides a framework for understanding how organisms allocate time and energy to tasks and traits in a way that maximizes their fitness.

Key trade-offs. The most important trade-offs include between present and future reproduction, quality and quantity of offspring, and mating effort and parental effort. LHT illuminates the important effects of ecological factors such as food supply and mortality hazards on optimal life history strategies.

Integration with evolutionary psychology. The integration of LHT with evolutionary psychology provides a means for uncovering psychological adaptations designed to make important budget allocation trade-offs. It also promises to reveal how different psychological mechanisms are linked with each other, illuminated by an economic cost-benefit analysis of selection pressures.

9. Domain specificity is supported by cognitive psychology and neuroscience.

They document evidence from cognitive psychology and neuroscience that strongly supports a key foundational premise of evolutionary psychology, namely, that humans possess, in their words, “a federation of evolved competencies.”

Domain specificity. Humans possess a federation of evolved competencies, each specialized for solving a different adaptive problem. These competencies are domain-specific, meaning they are tailored to process information and generate behavior in a particular domain.

Evidence from cognitive psychology and neuroscience. Evidence from cognitive psychology and neuroscience strongly supports the notion of domain specificity. Specific inference systems possess semantic knowledge, a specialized learning logic, a dedicated set of developmental pathways, and a close correspondence with specific adaptive problems solved.

Intuitive ontology. Intuitive ontology—adaptations for different domains of information—is a vehicle for illuminating the tight integration of neural, developmental, and behavioral components of evolved psychological mechanisms. Evolved competencies are more fine-grained than broad ontological categories imply.

10. Controversies in evolutionary psychology stem from misconceptions.

Hagan clarifies the notions of modularity and specificity and refutes common criticisms of these notions.

Recurrent controversies. Recurrent controversies surrounding evolutionary psychology include the conflation of levels of analysis (e.g., selfish genes versus selfish people), misunderstandings about the concept of the environment of evolutionary adaptedness (EEA), and enduring confusions about the false nature-nurture dichotomy.

Clarifying misconceptions. Many criticisms of evolutionary psychology are based on misconceptions about the field's conceptual foundations. By clarifying these misconceptions, the controversies can be resolved.

Political implications. Worries about the political implications of evolutionary psychology are unfounded. A true science of the human mind might indeed provide tools that potentially challenge and undermine values people hold near and dear.

Last updated: February 28, 2025