Home       SAPA Project Test       Papers

The Evolution of Evolutionary Psychology: From Sociobiology to Evolutionary Psychology

Melissa Seltin
Northwestern University

The theory of evolutionary psychology has generated much debate among both psychologists and philosophers. Therefore it is imperative that evolutionary psychology be evaluated in detail. In doing so, one is forced to examine its forerunner, sociobiology, and also question the concept of a good theory. Metatheory dictates that a good theory should be simple, accurate, fruitful, consistent, etc. Sociobiology, although strong in its Darwinian foundations, is highly criticized as being limited in scope and difficult to falsify. Evolutionary psychology is also criticized as being difficult to falsify, but scientists commend this theory for its fruitfulness and its ability to encompass many different fields of psychology while connecting psychology to the more hardcore sciences.

The field of psychology in general has been criticized by the scientific community as being unscientific, because disorganization and bickering among theorists minimizes the strengths of each individual theory. One theory, evolutionary psychology, claims to unify the various branches of psychology. Buss (1995) explains, "Because all behavior depends on complex psychological mechanisms and all psychological mechanisms at some basic level of description are the result of evolution by selection, then all psychological theories are implicitly evolutionary psychological theories" (p. 2). However, among psychologists, this claim is heavily debated and the field readily criticized. Therefore, it is imperative to examine evolutionary psychology's forerunner, sociobiology, and to dissect the field of evolutionary psychology itself. In doing this one must decide if both sociobiology and evolutionary psychology fit the various metatheory criteria. Metatheory dictates that all theories should be applicable, progressive, consistent, broad in scope, simple, and accurate.


Sociobiology is the study of the biological determinants of social behavior, based on the theory that such behavior is often genetically transmitted and subject to evolutionary processes. It stresses the importance of behavior and is committed to the theories of the adaptationist program. The adaptationist program assumes that certain creatures or groups of creatures currently exist because their past relatives possessed certain phenotypic traits that they were able to pass on to future generations.

According to Lewontin (1979), sociobiologists work under the assumption that "evolution of a species and community does in fact lead to high adaptation, high fitness, maximum intrinsic rate of increase, or some other attribute of the population related to reproductive success of individuals." Therefore it is the task of the individual theorist to decide what characteristics of the organism would be optimal given the state of the environment (p. 5). Note, that by using the term "nature" one is often referring to environment. Take for example the selection for black moths during the Industrial Revolution. When normally white trees became covered with soot due to factory pollution, the white moths became sparse, for they were easily sighted and eaten by birds. But the previously black moth minority population quickly increased as they were easily camouflaged by the soot. This exemplifies the theory of natural selection. The theory of natural selection is well established in scientific circles and rarely questioned.

In 1975, Wilson published Sociobiology, which was highly debated among theorists of the time. However, one no longer hears that psychology will be encompassed by sociobiology; rather psychology has incorporated some sociobiological theses while rejecting the more extreme assertions (Anker, 1987, p. 426). This is evident to those who have taken courses in various fields of psychology. Since 1975, evidence of genetic influence on behavior and acceptance of the theory has increased steadily. However, because of the general form of sociobiological argument, many remain skeptical.

Methods of Sociobiology

Sociobiologists begin like many psychologists. They describe the behavioral phenotype of a species. A phenotype is the type of behavior one can see clearly. But like genetic phenotypes, one must realize that what is seen is sometimes superficial and often lacks the deeper, less obvious perspective. Once they do this, they must design an adaptationist story to explain that the circumstances that would cause individuals to act in a certain way would actually benefit the individual's or group of individuals' reproductive success. Kitcher (1987) states, "Another common indictment of sociobiology is that it pursues an illegitimate adaptationist program, in which the evolutionary process is regarded as generating optimal phenotypes" (p. 66). However, it must be noted that sometimes there is no optimal phenotype available. Other times the optimal phenotype or genotype is hidden within a heterozygous pair. One example of this would be the protection from malaria due to a combination of the dominant and recessive genes for sickle cell anemia. Sickle cell anemia is present only when two recessive genes are present. Therefore, genetic protection from sickle cell anemia is hidden within a heterozygous pair. However, they then must prove this behavior to be genetically transmittable. But this is highly problematic, and sociobiology suffers from a number of serious methodological and epistemological problems (Lewontin, 1979, p. 6). For example, how does one prove that circumstances once existed when it is impossible to determine specific environments of the past?

Sociobiologists must first decide how the evolution of an organism is to be divided. Should it be divided according to function or physiological location? Lewontin (1979) argues that evolution cannot select for mental processes, only physical traits. As we will see later, evolutionary psychologists have objections to this assumption. It is argued that although mental constructs are not real objects, they can alter the future course of evolution. But Lewontin is quick to say that this happens more in the evolution of plants than in humans.

Criticisms of Sociobiology

Others have argued that sociobiology can be considered racist. Take for example the controversial book The Bell Curve, which attempts to correlate race and intelligence. Some philosophers and critical scientists say that sociobiology lacks predictive qualities. Others say that it is too limited to animals and has little value in reference to human beings. There remain, however, philosophers and other theorists who see sociobiology as a rationalization for the misbehaviors of both individuals, in the case of rape for example, and of society, for instance, the exploitation of women and children (Anker, 1987, p. 426). This was, however, never the intent of sociobiologists. Buss describes some of the errors of sociobiology, and how it differs from evolutionary psychology.

Sociobiology Versus Evolutionary Psychology

Buss (1995) begins by saying, "Although sociobiologists and evolutionary psychologists do share the same basic evolutionary theory in its modern instantiation as inclusive fitness theory, they depart in ways that are crucial for psychology" (p. 9). Specifically, sociobiologists believe that the main goal of humans is to increase reproductive success, to be "fitness maximizers." However, evolutionary psychologists believe humans to be "adaptation executors" or "mechanism activators." They believe the main goal of human beings is to solve the problems of survival that aid in reproduction and improve fitness. Notice this is very different from Buss (1991) who emphasizes that it is the sociobiologist who argues that humanity's main goal is reproduction. Evolutionary psychology is best regarded as a theory about origins, rather than the content of human nature (p. 463). Evolutionary psychologists specifically examine the causal processes that create specific mechanisms and not the mechanisms themselves.

Why can humans not be fitness maximizers? Buss (1995) answers this by saying that psychologists can not track fitness within a lifetime, much less action by action. Fitness is too nondescript, and contributors to fitness vary across species, sexes, ages, ecologies, and adaptive domains (p. 10). There are too many variable factors to specify what exactly contributes to fitness. He also describes the "sociobiological fallacy" by stating that many sociobiologists have skipped or neglected the 'psychological level' of analysis (p. 10). Simply, they have concentrated too much on the end product of behavior, and have failed to question why humans developed the behaviors in the first place. For example, why are people social animals? How do humans choose mates? Why do people behave in altruistic ways?

Evolutionary Psychology

The first aspect of evolutionary psychology refers to its reliance upon natural selection. This specific theory is rarely debated and is so widely accepted that the very domain of biology is reliant upon it. Buss (1991) states that evolutionary psychology also stresses that there is no such thing as a "purely environmental or situational cause of behavior" (p. 461). This aspect refers to hormonal and other physical causes or mechanisms of behavior. It is hypothesized that such mechanisms have evolved because they have behavioral consequences. One example of this would be the fight-or-flight response to danger. When a person encounters a dangerous situation, the sympathetic nervous system releases hormones that enable humans to react quickly to the stimuli: increased breathing, heart rate, etc. This is evolutionarily adaptive as it aids people in escaping dangerous situations.

Biological Foundations

It must be noted, however, that some biological phenonema arise through processes other than natural selection. An example of this would be genetic drift, pleiotropy, or chance. Genetic drift occurs in cases where random changes take place within large populations of organisms. Pleiotropy involves the expression of multiple phenotypic traits as the result of one gene. For example, albino organisms, who lack pigment, are light in coloring and pink eyed. Buss (1991) also specifies that other mutations may be neutral with respect to natural selection, and thus endure without being adaptive (p. 466). For example, some physical characteristics in humans such as height or hair color are currently neutrally adaptive. Such characteristics do not maximize fitness or reproduction and do not improve our chance of survival. Therefore, natural selection cannot account for all biological phenomena, and differentiating among such phenomena is extremely difficult for evolutionary psychologists.

Buss (1991) specifies, "While general evolutionary theory broadly outlines what is unlikely to have evolved, it can rarely specify what must have evolved" (p. 464). Evolutionary psychologists are, however, extremely successful at accounting for individual differences. They argue that individuals differ in the adaptive strategies that they employ. These differences can be incidental by-products of such strategies or can result from noise within the system, for example mutations (Buss, 1991, p. 473). Like in groups of creatures, it is extremely difficult when studying individuals to differentiate between strategies that manifest randomly and those that are selected for. But what strategies do evolutionary psychologists employ to identify these adaptive strategies?

Methods of Evolutionary Psychology

Empirical methods used in evolutionary psychology are similar to those used in other areas of psychology: experimental methods, questionnaire methods, analysis of public documents, observations, and psychophysiological technology. Gangestad (1995) describes the approach evolutionary psychologists employ to understand adaptations:
first identify the recurrent structure of ancestral environments; then to identify specific adaptive problems that this recurrent structure would have posed for our ancestors to have solved; then to specify particular psychological architecture that would have solved those adaptive problems; and then to assess the fit of the behavior that these psychological mechanisms produce across different environments. (p. 40)
But this process may be difficult to achieve. First it is difficult, if not impossible, to accurately describe ancestral environments. Second the science of psychology itself is not equipped to identify psychological architectures, specifically at their deepest, genetic structure. If these two basic premises are not met, it would be impossible to then assess the mechanisms.

Mechanisms are divided and studied according to function. In doing this, evolutionary psychologists can analyze mechanisms in two directions: form-to-function or function-to-form. Sometimes they have available the physical mechanisms or the evolutionary benefit and must attempt to discover the psychological cause or evolutionary motive. Other times they know the psychological manifestations, but question the evolutionary benefit. But does this technique not lead to excessive approximations? It seems that evolutionary hypotheses are mainly speculative, resulting in an educated guess. Is there a way to truly know if a hypothesis is either correct or incorrect?


What makes a good theory? There has been much speculation on this issue. It is important that the theory be applicable, particularly in psychology. Westland (1978) states, "If science means 'knowledge', 'understanding', etc., it is difficult to see what a science of behavior can possibly be if the student of the subject is not enabled to employ his knowledge and understanding to achieve solutions to practical problems" (p. 6). Evolutionary psychology has been successful in explaining mating preferences. It is also successful in explaining fear mechanisms, and why certain things are feared and others are not. Because evolutionary psychology is so successful in explaining fear mechanisms, clinical treatments for anxiety disorders have also improved.

A good theory must also be progressive. The theory is progressive if it predicts some novel facts not foreseen by its predecessors (Kuhn, 1987, p. 198). Evolutionary psychology went one step further than its predecessor, sociobiology. Evolutionary psychology is best regarded as a theory about the origins, rather than the content, of human nature (Buss, 1991, p. 463). Therefore, it attempts to provide a physiological foundation for various mechanisms, phenotypes, and behaviors.

Not only is it progressive, but it is consistent. A theory should be consistent, both internally, and with other theories. Although there is some debate among evolutionary psychologists about specific hypotheses, this is normal and healthy to the development of a theory. There is no argument regarding the basic assumption concerning natural selection however. This is of the utmost importance, as natural selection is at the heart of evolutionary theory. Buss (1991) demonstrates the benefit of evolutionary psychology to other theories in his example regarding personality psychology:

Evolutionary theory can become a scientifically useful metatheory for personality psychology to the degree that human psychological mechanisms (a) operate according to different principles across different adaptive domains, (b) number in dozens, hundreds, or thousands, (c) are complex solutions to specific adaptive problems. (p. 461-462)
This is also evident in many other areas of psychology: social psychology, developmental psychology, cognitive psychology, and so on.

Good theories are also broad in scope. They extend far beyond the particular observations, laws, or subtheories they were initially designed to explain (Kuhn, 1987, p. 198). Although this branch of psychology is fairly young, it has incredible potential, especially if done in partnership with genetic studies currently underway. Not only are evolutionary psychologists discovering the evolutionary motives of behavior, they are discovering alternative strategies of behavior designed for the sole purpose of adapting to modern times. An example of this would be the current trend regarding obesity. Because humankind has become more dependent on machines for both the simple and the complex, its motor skills and physical fitness have atrophied, resulting in more obesity, heart disease, etc.

Evolutionary psychology also is simple; it brings order to otherwise confusing information (Kuhn, 1987, p. 198). It literally brings nearly all fields of psychology together. In some respects it unites the science of psychology with the other sciences, specifically biology, due to its genetic components. It is successful in explaining behaviors that may not seem beneficial upon superficial inspection, i.e. altruistic behaviors.

Most importantly, a good theory should be accurate. Kuhn (1987) emphasizes, "Within its domain, that is, consequences deducible from a theory should be in demonstrated agreement with the results of existing experiments and observations" (p. 198). It is questionable whether evolutionary psychology meets this particular criterion. Although the empirical methods are generally acceptable within the psychological community, one cannot help but wonder if psychological methods are able to either falsify or prove evolutionary hypotheses. There are still many anthropological questions left unanswered--for example, ancestral weather and environmental conditions or particular social idiosyncrasies, and unfortunately speculation is prevalent. Historical environments, situations, and predicaments can be speculated about at best. Work in genetics, for example, the Human Genome Project, is still incomplete and thus in many respects incoherent. Although thought processes are an important aspect of evolutionary psychology, also important is an understanding of the physical mechanisms that enable such thought mechanisms. Therefore a genetic map and full understanding of neural and hormonal pathways is imperative. Work in evolutionary psychology has an extremely useful potential, however, and that cannot be overlooked.


Sociobiology has provided the strong Darwinian foundations which have contributed to the development of evolutionary psychology. Evolutionary psychology did not seek to replace sociobiology, but instead it strengthened and expanded upon the strongest sociobiological theses, incorporating these new and improved ideas into its infrastructure. At the same time, it has also incorporated biological, physiological, and biochemical hypotheses, thus encompassing the hard core sciences into the field of psychology. In doing this, concrete data that can be seen (by microscope) and proven using techniques other than human observation are now available to psychology. Sociobiology has evolved, and born into the world of science is a new and improved theory, evolutionary psychology.


Anker, J. D. (Ed.; 1987). Systems and theories in psychology. New York: McGraw Hill.

Buss, D. M. (1991). Evolutionary personality psychology. Annual Review of Psychology, 42, 459-491.

Buss, D. M. (1995). Evolutionary psychology: A new paradigm for psychological science. Psychological Inquiry, 6, 1-30.

Gangestad, S. W. (1995). The new evolutionary psychology: Prospects and challenges. Psychological Inquiry, 6, 38-41.

Kitcher, P. (1987). Précis of Vaulting ambition: Sociobiology and the quest for human nature. Behavioral and Brain Sciences, 10, 61-100.

Kuhn, T. S. (1987). Objectivity, value judgment, and theory choice. In J. A. Kourany (Ed.), Scientific knowledge: Basic issues in the philosophy of science (pp. 197-207). Belmont, CA: Wadsworth.

Lewontin, R. C. (1979). Sociobiology as an adaptionist program. Behavioral Science, 24, 5-14.

Margolis, J., Manicas, P. T., Harre, R., & Secord, P. F. (1986). Psychology: Designing the discipline. Oxford: Blackwell.

Stagner, R. (1988). A history of psychological theories. New York: Macmillan.

Westland, G. (1978). Current crises of psychology. London: Heinemann Educational Books.

Last modified August 1998
Visited times since July 2001

Home to Personality Papers

Home to Great Ideas in Personality