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Darwin's Definitions

The vocabulary of evolutionary psychology

PDPics / Pixabay
Source: PDPics / Pixabay

As is true in any field, evolutionary psychology has its own jargon (with jargon meaning group of technical terms that have specific meaning in the confines of a particular discipline). If you want to understand the field of evolutionary psychology, you need to speak the language! Below is a list of key terms and definitions - provided as a guide to help people understand this field.

  • Adaptation - Some evolved feature of an organism that came about because it helped the ancestors of that organism increase their ability to survive and/or reproduce.
  • Adaptive Hurdle (also Selective Pressure) - In the evolution of living organisms over time, an adaptive hurdle is a feature of the environment that impedes survival and/or reproduction of an organism (and it ultimately (often) leads to the evolution of adaptations shaped to address that hurdle).
  • Altricial Species - A species in which the young require relatively high amounts of parental investment to survive.
  • Altruism - Behavior that increases the reproductive success/survival of another at a cost to one’s own long-term reproductive success.
  • Costly signal - Some physical of behavioral feature of an organism that provides obvious costs to survival but that, indirectly, provides reproductive-based benefits.
  • Conspecific - A member of one’s own species.
  • Environment of Evolutionary Adaptedness (EEA) - The ancestral conditions of an organism that characterized the environment that surrounded the ancestors of that organism across the bulk of evolutionary time.
  • Evolutionary Arms Race (also Antagonistic Co-Evolution) - An evolutionary arms race exists when an adaptation in one species evolves to combat an adaptation in some other species that is located in its same environment. Over time, that other species, then, evolves counter-adaptations that essentially “combat” that first adaptation. And so on.
  • Evolutionary Mismatch - A situation in which the modern conditions of an organism are mismatched from the conditions that characterized the ancestral environments of that organism in important ways.

  • Extended Phenotype - Changes in the environment of an organism that result from members of the species altering the environment of the organism through behavioral means.

  • Fitness - The tendency for some feature of an organism to, literally, “fit” with the features of the environment that characterized the ancestors of that organism. Often defined in terms of the “ability to lead to increased reproductive success.”

  • Game Theory - The idea that there are optimal ratios of various phenotypes that tend to evolve, such that the long-term adaptiveness of one each of the various phenotypes is likely about equal to the long-term adaptiveness of the alternative phenotypes - based on the idea of some optimal equilibrium that emerges over evolutionary time.

  • Genotype - The DNA coding that exists in each of the cells of a particular organism.

  • Hyperadaptationism - The idea that some evolutionary scholars, at times, apply the concept of adaptation more so than is warranted.

  • Inclusive Fitness - The overall reproductive success that is achieved by an organism, including its ability to increase the likelihood of its own genes getting into the future and the ability of its genes as they exist in the bodies of kin (i.e., related individuals) getting into future generations.

  • Intra-Sexual Competition - The process by which individuals within one sex of a species compete with each other for access to members of the opposite sex.

  • Inter-Sexual Selection - The process by which some features of an organism come to shape members of one sex of a species because these features are attractive to potential mates.

  • Kin-Selected Altruism - Helping a kin member, who shares genes with oneself, in a way that ultimately helps one’s own long-term reproductive success (by passing on genes that the kin shared with the helper).
  • Life History Strategy -The idea that organisms adopt either a fast or a slow approach to life, depending on environmental circumstances. Animals that experience unstable, harsh conditions are more likely to pursue a fast life history strategy (by reproducing often and early in life) while individuals who are surrounded by stable environmental conditions are more likely to pursue a slow life history strategy (reproducing only a few times and giving much care to each offspring).
  • Natural Selection - The process by which some features of organisms (features that lead to increased reproductive success) are selected by nature across time and come to, ultimately, characterize a particular species.
  • Naturalistic Fallacy - A term used by evolutionary psychologists to refer to critics of the field who seem to think that concepts developed by evolutionary psychologists that characterize how people “naturally are” are being framed, instead, as “how things should be.”
  • Niche - A specific part of an environment that serves as the home for some particular species or set of species. It has its own particular details, bearing on such features as temperature, plant life, animal life, geological features, etc.
  • Parental Investment Theory - A theory, put forth by Robert Trivers (1971), suggesting that the amount of investment that a members of a particular species must invest into successful parenting will shape the social and mating-relevant processes that come to characterize the members of that species.
  • Phenotype - The physical, behavioral, or otherwise observable manifestation of an organism’s genotype.
  • Precocial Species - A species in which the young of a species require relatively little amounts of parental investment to survive.
  • Reciprocal Altruism - Helping another with an implicit expectation of receiving help back at a future point.
  • Reproductive Success - An outcome associated with the production of offspring, grand-offspring, etc. Ultimately, this concept is Darwin’s bottom line - features of organisms that increase reproductive success are factors that are adaptive and that, ultimately, will be more likely to exist into the future.
  • Sexual Selection - The process by which some feature of an organism is retained as part of the species because it confers reproductive benefits to individual organisms that have this feature.
  • Spandrel - A feature of an organism that is species-typical but that evolved only as a by-product of an adaptation (and is not an adaptation in and of itself)
  • Strategic Pluralism - The idea that multiple strategies, all shaped to solve the same survival or reproductive-based problem, can evolve within a species. These may be physical and/or behavioral.

Bottom Line

Of course, this list is remarkably incomplete—but it’s a start! Want to know more about the field of evolutionary psychology? You might want to check out Evolutionary Psychology 101. Happy Reading!


Geher, G. (2014). Evolutionary Psychology 101. New York: Springer.

Trivers, R. L. (1971). The evolution of reciprocal altruism. Quarterly Review of Biology, 46, 35–57.

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