Individual Differences


Evolutionary Psychology
Psychological Aspects of Human Evolution

Last updated:
01 Sep 2003



Examples of important aspects of human psychology which are unique & have evolutionary explanations

How can we understand the phenomenon of obesity in Western society?

How can we understand the phenomenon of anorexia nervosa in Western society?

Recommended Links



In the distant future I see open fields for far more important researches. Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation.
- Charles Darwin, 1859, p. 449.

The tabula of human nature was never rasa and it is now being read.
- William D. Hamilton,  1997

"The goal of research in evolutionary psychology is to discover and understand the design of the human mind. Evolutionary psychology is an approach to psychology, in which knowledge and principles from evolutionary biology are put to use in research on the structure of the human mind. It is not an area of study, like vision, reasoning, or social behavior. It is a way of thinking about psychology that can be applied to any topic within it."
- Cosmides & Tooby, 1997

"Most of what we strive for in our modern life uses the apparatus of goal seeking that was originally set up to seek goals in the state of nature."
- Richard Dawkins, Darwin's Dangerous Disciple, An interview by Frank Miele

"But the likelihood is that, in 100,000 years time, we shall either have reverted to wild barbarism, or else civilisation will have advanced beyond all recognition--into colonies in outer space, for instance. In either case, evolutionary extrapolations from present conditions are likely to be highly misleading."
- Richard Dawkins, The Evolutionary Future of Man, (go to Future Psychological Evolution)


Evolutionary perspectives on human psychology form part of the more general theory of natural selection.  To understand evolutionary psychology, it is necessary to have a basic understanding of genes, inheritance, and the principles of natural selection (go to the 4 principles of natural selection).  Using these basic concepts, more complex explanations can be constructed about how different aspects of human psychology have come about.  Such insights and understandings can be found in a range of diverse, but related fields, including:

  • sociobiology (biological explanations for social behavior)

  • evolutionary psychology (evolutionary understandings of human psychology; some say evolutionary psychology is just a new name for sociobiology, a concept which has sparked considerable intellectual controversy; for more, go to the Evolution of Evolutionary Psychology)

  • anthropology (the study of human societies)

  • paleo-psychology (the psychology of prehistorical human beings)

  • ethnobotany (the use of plants in primitive societies)

  • behavioral genetics (compare similarities in personality between individuals who are and are not genetically related, or related to a different degree)

Whilst it has been long recognized that human morphology is a function of evolutionary selection, it is only more recently that human behavior and consciousness have come to be examined in light of their evolutionary adaptivity (Panksepp & Panksepp, 2000).


Such understandings, however, can be quite profound and consequently also quite controversial.  The kinds of questions that fall within the province of evolutionary psychology include:

  • How, why, and when did human consciousness evolve?

  • Why are there notable differences between the psychology of men and women? (such as greater outward hostility by males and greater neuroticism in females?)

  • What are the adaptive explanations for seemingly negative, destructive human behaviors such as aggression, self-harm, etc.?

  • What are the adaptive explanations for human behaviors which seem, at least on the surface, somewhat at odds with "survival of the fittest" notions, e.g., altruism, anorexia, etc.

  • Is human consciousness evolving?  What can be learned from past patterns of evolution in the human psyche and what can we expect for the future of human consciousness?

  • Are there real psychological differences between the races?  If so, what are they?

  • To what extent is human intelligence inherited and to what extent is it influenced by the environment?

  • What are the evolutionary psychological explanations for the common human phobias?

Note that many psychologists, sociologists, anthropologists, and others are wary of evolutionary perspectives on the human mind and behavior (e.g., see Panksepp & Panksepp, 2000).  The main criticism seems to be that evolutionary psychological theories generalized too much from studies of animals and the general principles of evolution, i.e., that it isn't good science.  There are also political, social, and religious criticims (not to mention personal ones!) - essentially they amount to a rejection of a perceived neo-Darwinianism in evolutionary psychology.  What does this mean?  Basically, it seems there is a fear that it is harmful to society for humans to be understood as creatures whose behavior can be understood as at least partially the result of genetic and biological causes.


These debates exist at least in part because it is incredibly difficult to actually test out many evolutionary psychological ideas in a conventional, scientific, experimental sense.  Evidence comes from a range of sources, including fossils (e.g., brain size), genetics, animal studies, and paleo-anthropological research (e.g., study of human artificacts, including tools and art) and related evidence about climate, plant and animal evolution.  Conventional psychological research in evolutionary psychology, however, is often necessarily correlational, which is generally not as strong as experimental research.  Exciting new evidence.  For example, recent modern forms of forensic study allow news kinds of study of past fossilized and semi-preserved human remains.  Read about the remarkable recent find of "Otzi", a 5,300 year body of a man frozen in ice in the European alps.


The evolutionary evidence for human psychology, then, is necessarily based on an incomplete jig-saw puzzle, which inevitably includes conjecture and somewhat circumstantial evidence, mixed with scientific findings, as well as more esoteric psychological insights and speculations.


The real potential, I think, of evolutionary psychology is when it is explored in a multi-disciplinary sense.  For example, the work by Jung on collective unconsciousness and archetypal theory, which was extended in a social and cultural sense by Joseph Campbell's work on cross-cultural mythic similarities, provide rich material for integration with evolutionary psychological principles.  This idea is consistent with a comment by Richard Dawkins (in the Evolutionary Future of Man) that "it may be that brain hardware has co-evolved with the internal virtual worlds that it creates. This can be called hardware-software co-evolution."  Thus, viewed as a platform for human psychology, evolutionary principles offers a rich, deep bed of understanding a long history of the species, into which can be situated more specific, micro-theories, such as from cognitive psychology, behavioral psychology, etc.


Nevertheless, we must not lose sight of the many alternative explanations, such as social psychological principles (e.g., social learning) for explaining behaviors such as aggression.  There are many aspects of personality and behavior which are often best understood, at least from a practical, , functional, or clinical perspective, as caused by biological, cognitive learning, or humanistic forces.  Equally, however, we must examine in a fair light, the extensive, eclectic evidence and rather all-encompassing explanations suggested by the greatest scientific theory of all time - natural selection.  The forces of nature, expressed over time in the genetic code, according many evolutionary psychologists, play (and continue to play) a fundamental and often underestimated role in the shaping the human psyche and human behavior.


A useful read at this point is Edward Hagen's response to the frequently asked question "Isn't is true that we can't know what really happened in the distant past, therefore evolutionary psychology is a waste of time?"


Also note that evolutionary psychologists do not claim that all behaviors can be explained by evolutionary principles - clearly other factors such as environmental learning are also important.  Read "Do evolutionary psychologists think that everything is adaptation?" (Edward Hagen).


The major assumption in evolutionary psychology is that psychological adaptations are not qualitatively different from physical adaptations in evolution.  Unless one wishes to argue for mind-body dualism, this assumption can be readily accepted.


Psychological adaptations basically refer to human's methods of inputting information, processing and analyzing information, the making of decisions, and the execution of behavior.  Behavior, remember, includes all actions, including acts of language and communication, reproductive behaviors, food-seeking behavior, and so on.


A couple of examples may help.  You may also be interested to read Edward Hagen's "How can we identify psychological adaptations?".


Examples of important aspects of human psychology which are unique & have evolutionary explanations


There are several aspects of human psychology which make homo sapiens stand apart from the other animals, and which attract much of the focus of those interested in evolutionary psychology:

  • human intellectual capacity - overall brain size, large frontal cortex, more convolutions, etc. all imply that a greater capacity to process information have been arguably the most dominant psychological characteristic selected for during the evolution of the human species

  • the sophisticated use of language - interestingly, humans seem to come pre-wired to learn language, but not with a pre-set language.  During the remarkable period of neural plasticity during a child's early years, the child has a greater capacity for acquiring language that at any other period of his/her life.

  • capacity for emotion and affect - humans are fundamentally emotional animals, experiencing great heights of ecstasy and depths of depression.  Compared to other animals, humans are both more likely to have excesses of joy (e.g. manic depression) and excesses of sadness (e.g., unipolar depression).  No other animals are known to intentionally kill themselves.  Humans are the only animals known to exhibit such destructive tendencies towards their surrounding environment and fellow members of their species.  On the other hand, humans also display at times some remarkably altruistic behaviors which, on the surface, may not seem particularly adaptive. 

  • complex courting & sexual behaviors - humans are the only animal, it seems, which are so addicted to sex, even when it doesn't seem to be for reproductive purposes; human females are the only primates to have permanently engorged breasts, and the male penis is proportionately larger than in any other species.  Did you know that the most common word searched for on the net is "sex", closely followed by "porn" and other related words (to see a full list, go to  It seems that the sexual drive in humans interacts with the large intellectual capacity, the sophisticated use of language (think of all the love poetry out there), the drive to care (and the need to care for offspring for a long-time), and the capacity for emotion.  No other animals exhibit the complex sexual disorders and deviations evident in humans.  There is considerable examination of human aggression & violence, including sexual aggression such as rape, within evolutionary psychology.

How can we understand the phenomenon of obesity in Western society? 


Obesity in western society is quite readily explained by evolutionary principles.  For most of human evolution, obtaining sufficient food and nutrition was a daily battle, and daily life was physically rigorous.  Thus, the human body become highly efficient at storing excess energy from excess food intake.  However, the dramatic cultural evolution in Western lifestyles has made copious amounts of food readily available at the same time as reducing physical daily demands to very low levels.  The result is that people in Western society are now exhibiting all-time record levels of obesity and related eating disorders.  61% of Americans are overweight or obese - what's more - the incidence of obesity increased 61% in the period from 1991 to 2000.  Likewise Australia is one of the most obese countries in the world, with obesity in children increasing by 100% in the past 10 years; 25% of Australian children are overweight or obese.  Obviously obesity is not particularly adaptive, but cultural evolution has outstripped genetic evolution, giving rise to this phenomenon (Feist & Feist, 2002). 


You may be interested to read a recent news report about new research that has found a relationship between body fat % and urban design in America.


How can we understand the phenomenon of anorexia nervosa in Western society?


The evolutionary explanation for obesity seems obvious and straightforward.  However, a greater challenge for evolutionary psychology would be to account for anorexia nervosa, seemingly the opposite problem.


During human evolution it would not have been adaptive to always eat everything in site, but rather it would have important to effectively ration during lean times, as well as eating up during more abundant times.  Thus, the capacity to "go without food" would have been important for survival.  This is a difficult proposition, because it implies the development of a higher instinct than the immediate instinct to gratify hunger. 


Given that humans are creatures that evolved in social groups, presumably the capacity to "go without food" for the sake of the group would have been socially reinforced.  Those who didn't possess this capacity would have been punished by the group, if they had sufficient power.  Thus, it can seen that eating food would have evolved with a complex individual and social psychology associated.  The immediate pleasure and gratification associated with eating would have been tempered by higher faculties and social norms emphasizing eating a minimum for current survival in order to help maximize longer likelihood of survival. 


In the modern human, if there is an overactive super-ego or over susceptibility to social messages about "eating less", then maladaptive behavior behavior patterns such anorexia and binge eating / vomiting can manifest around the "withholding of food despite hunger" disposition which has evolved in humans.

Recommended Links


Bethell, T. (2001). Against sociobiology. First Things, the Journal of Religion & Public Life, January.

Cosmides, L. & Tooby, J. (1997). Evolutionary psychology primer.

Darwin, C. (1859). The origin of species by means of natural selection or the preservation of races in the struggle for life.

Feist, J., & Feist, G. J. (2002). Theories of personality (5th ed.). New York: McGraw-Hill.

Panksepp, J., & Panksepp, J. B. (2000). The seven sins of evolutionary psychology. Evolution and Cognition, 6(2), 108-131. [.pdf]

Wright, A. (2003). The sociobiology of information architecture.