Evolutionary Perspectives on Personality
Chapter 8: Evolutionary Perspectives on Personality
Evolution and Natural Selection
All humans today originate from an unbroken line of ancestors who successfully accomplished two critical tasks: they survived to reproductive age and they reproduced. This success carries with it adaptive mechanisms developed throughout our evolutionary history that contributed to the survival of our ancestors. Therefore, human nature, along with individual human personality, can be understood as comprised of a collection of evolved mechanisms that aided in these survival and reproductive efforts.
Natural Selection
Charles Darwin revolutionized biological thought by introducing the theory of natural selection, which explains how adaptations in organisms are created and how changes occur over time. Key points of this process include:
A greater number of offspring are produced than can survive to adulthood and reproduce.
Variants or changes that enhance an organism's ability to survive and reproduce tend to yield more descendants who inherit these advantageous traits.
Over time, the successful variants are selected, while unsuccessful variants are filtered out.
As a result, successful variants gradually come to characterize entire species.
Adaptations are defined as inherited solutions to survival and reproductive problems posed by the hostile forces of nature.
Sexual Selection
Darwin also recognized that certain evolutionary mechanisms, particularly in the context of mating success, could appear to threaten survival. A notable example is the peacock’s elaborate plumage or the stag’s large antlers. To address this, Darwin proposed the concept of evolution by sexual selection, where these characteristics evolved primarily because they increased an individual's mating success.
Forms of Sexual Selection
There are two primary forms of sexual selection:
Intrasexual Competition: Members of the same sex compete with one another for mating access to members of the opposite sex.
Intersexual Competition: Members of one sex choose their mates based on preferred qualities exhibited by the opposite sex.
Genes and Inclusive Fitness
Definition of a Gene
A gene is described as a discrete packet of DNA inherited from parents, serving as the smallest unit of inheritance that can be passed on without change. The discovery of genes has critical implications for understanding natural selection and sexual selection as two distinct but closely related processes.
Differential Gene Reproduction
Differential Gene Reproduction: This refers to the relative reproductive success of individuals compared to others within the same environment.
Inclusive Fitness Theory: Initially proposed by Hamilton in 1964, inclusive fitness takes into account not only personal reproductive success, measured by the number of offspring produced, but also considers the reproductive successes of genetic relatives weighed by their genetic relatedness.
Products of the Evolutionary Process
From an evolutionary perspective, the outcomes of the evolutionary process can be categorized into:
Adaptations: The primary results of evolutionary selection.
Byproducts of Adaptations: Incidental effects of adaptations that are not recognized as direct adaptations.
Noise or Random Variation: Characteristics that remain neutral with respect to selection (for example, the shape of human earlobes).
Evolutionary Psychology
Premises of Evolutionary Psychology
The field of evolutionary psychology is based on three primary premises:
Domain-Specificity: Adaptations arise from the evolutionary process specifically to resolve distinct adaptive problems.
Numerousness: It is expected that many psychological adaptations exist due to the diverse adaptive challenges humans have faced.
Functionality: Psychological adaptations are inherently designed to fulfill particular adaptive goals.
Empirical Testing of Evolutionary Hypotheses
There exists a hierarchy of analytical levels within evolutionary psychology that includes:
General evolutionary theory
Middle-level evolutionary theories
Specific hypotheses that yield testable predictions
Modes of Conducting Empirical Research
Research can be conducted primarily through two approaches:
Deductive Reasoning Approach: A “top down,” theory-driven method.
Inductive Reasoning Approach: A “bottom up,” data-driven method.
Both approaches are regarded as valid methodologies in scientific research.
Human Nature
Human nature, through the lens of evolution, is understood to be a byproduct of the evolutionary process. Psychological mechanisms that have historically led to better survival and reproduction outlive and out-replicate those mechanisms that have not been as effective.
Evolutionary Analysis on Human Nature
Examples that provide insight into the evolutionary analysis at the level of human nature include:
The Need to Belong
Helping and Altruism
Universal Emotions
Sex Differences
Evolutionary psychologists assert that males and females may exhibit similarities in areas where both sexes have historically confronted similar adaptive challenges. Conversely, they expect to see pronounced differences in those domains where men and women have faced different adaptive challenges.
Examples of Sex Differences
Specific examples of sex differences attributable to differing adaptive challenges include:
Aggression
Jealousy
Desire for Sexual Variety
Mate Preferences
Individual Differences
The analysis of individual differences presents challenges for evolutionary psychologists. Three evolutionary perspectives frequently explored include:
Environmental Triggers of Individual Differences
Heritable Individual Differences: Contingent on other traits
Frequency-dependent Strategic Individual Differences
The Big Five Traits and Evolutionarily-Relevant Adaptive Problems
The Big Five personality traits represent clusters of significant features within the “adaptive landscape” regarding other individuals. Humans have evolved mechanisms adept at detecting differences to better navigate social adaptive issues.
Limitations of Evolutionary Psychology
Challenges in Understanding Evolutionary Psychology
The adaptations we observe have been shaped over extensive periods; thus, it is often impossible to definitively ascertain the selective forces that acted upon humans.
Current psychological mechanisms serve as clues toward understanding our evolutionary past, though they may not provide complete clarity.
Evolutionary scientists are still early in their exploration of the nature, intricacies, and design qualities of evolved psychological mechanisms.
The evolutionary processes and conditions that shaped our ancestors differ considerably from those faced today, which can complicate the relevance of past mechanisms.
Competing Hypotheses
Formulating diverse, competing evolutionary hypotheses for the same phenomena is a common occurrence within the field, as it is in all sciences. Researchers are compelled to articulate precise, testable, and falsifiable hypotheses to determine validity through empirical data, which can be pitted against each other to find support. The claim that evolutionary hypotheses are untestable is mistaken; this issue extends across various fields of science.
Summary and Evaluation
To encapsulate the findings and theories discussed in this chapter:
Selection is central to understanding evolution, driving change within species over time.
Variants that result in greater genetic replication have a propensity to disseminate through populations.
Evolutionary psychology rests on three central premises: adaptations are domain-specific, numerous, and purposeful.
Methodological approaches in evolutionary psychology can be bifurcated into deductive and inductive methods.
Evolutionary psychology's application spans across all three levels of personality analysis—human nature, sex differences, and individual differences.
Despite its limitations, evolutionary psychology contributes valuable theoretical frameworks for the understanding of personality.