Evolution
This section provides a basic overview of the role of evolutionary theory in biology, evolutionary psychology, and evolutionary psychopathology.
Nothing in biology makes sense except in the light of evolution.
Evolutionary Theory
Biological evolution
Biological evolution is the change in the heritable characteristics of populations of organisms over successive generations. Biological evolution is caused by multiple processes, including natural selection, sexual selection, mutation, migration, and genetic drift.
Biological adaptations
Biological adaptations are phenotypic traits that were produced by selection processes in ancestral environments, and that produce beneficial effects for the organisms that possess them. Animal camouflage is a common example of a biological adaptation. Some biological adaptations are the result of gene-culture coevolution.
Relativity of Adaptations to Environments
Whether a trait or behavior is adaptive or maladaptive depends on the environment in which an organism lives. A thick fur coat may be beneficial in an arctic environment, but it is potentially fatal in a tropical environment. The relativity of adaptations to environments is made obvious by climate change, which can alter the adaptive significance of a trait or behavior from being adaptive to being maladaptive, often with fatal consequences.
What is evolutionary psychology?
Evolutionary psychology
Evolutionary psychology is the application of evolutionary theory to the investigation of psychological phenomena. Researchers in evolutionary psychology conceptualize species-typical mental processes like perception, cognition, emotion, and motivation as evolved capacities that perform adaptive functions.
Psychological adaptations
Psychological adaptations are psychological traits or behaviors that were produced by selection processes in ancestral environments, and that produce beneficial effects for the individuals that possess them. The prepared learning for fear of snakes among humans and other primates is a common example of a psychological adaptation.
Environment of Evolutionary Adaptedness
Biological and psychological adaptations can be understood as evolved solutions to the challenges that organisms faced in their environment of evolutionary adaptedness, i.e. a statistical composite of the selection pressures that organisms encountered over the course of their evolutionary history.
Ancestral Human Environments
For ancestral humans (including Homo sapiens as well as other species within the Homo lineage), the environment of evolutionary adaptedness is largely a composite of the selection pressures found in the grassland and woodland Pleistocene habitats of Africa. In that environment, ancestral humans faced a wide range of ecological and social challenges, including the challenges of hunting, foraging, avoiding predators, finding mates, forming alliances, raising offspring, producing tools, and many others.
The Principle of Adaptive Behavior
Many of the diverse theories and findings in evolutionary psychology can be encapsulated in the principle of adaptive behavior, which states: Evolution has shaped mental and physiological processes to control adaptive behaviors.
The principle of adaptive behavior highlights the fact that, over human evolutionary history, species-typical mental processes like perception, cognition, emotion, and motivation were selected for largely because of their role in controlling adaptive behaviors.
In ancestral environments, adaptive behaviors promoted an individual’s biological fitness, i.e. the likelihood of survival and reproduction. In modern environments, adaptive behaviors also promote an individual’s physical and mental health.
The Principle of Adaptive Behavior
What is evolutionary psychopathology?
Evolutionary psychopathology
Evolutionary psychopathology is the application of evolutionary theory to the investigation and treatment of mental disorders. Researchers working within evolutionary psychopathology have applied evolutionary theory to a wide range of mental disorders, including mood disorders, anxiety disorders, neurodevelopmental disorders, psychotic disorders, eating disorders, and substance use disorders.
Mental disorders
From the perspective of evolutionary psychopathology, mental disorders are disturbances to the mental and physiological processes that control adaptive behaviors, resulting in adaptive deficits in perception, cognition, emotion, motivation, behavior, and/or physiological regulation. Specific mental disorders can be understood as characteristic patterns of disturbance to the mental and physiological processes that control adaptive behaviors.
The Principle of Adaptive Significance
Many of the diverse theories and findings of evolutionary psychopathology can be encapsulated in the principle of adaptive significance, which states: Many clinical symptoms and syndromes commonly identified as psychopathology can be either adaptive or maladaptive, depending on the context.
Consider anxiety, for example. In low-risk contexts, anxiety is often maladaptive. However, in high-risk contexts, anxiety can be adaptive—even life saving. This is arguably why anxiety was selected during human evolutionary history—to protect people from the dangerous consequences of high-risk events and behaviors.
Unlike mainstream approaches to psychopathology, evolutionary psychopathology does not assume that all clinical symptoms and syndromes are necessarily maladaptive. Under the right circumstances, even clinical symptoms like low mood and anhedonia can be adaptive. This is discussed further in the page on depression.
The following metaphor may be helpful: Mainstream approaches to psychopathology regard clinical symptoms and syndromes as akin to a seizure. Seizures are not adaptive—they are not beneficial in any environment.
On the other hand, evolutionary approaches to psychopathology regard many clinical symptoms and syndromes as akin to a fever. In the context of high-pathogen load environments, fevers are adaptive, since they help destroy dangerous pathogens. With this in mind, the principle of adaptive significance amounts to saying that many clinical symptoms and syndromes are more like fevers than they are like seizures.
The principle of adaptive significance is perhaps the single most important and innovative contribution of evolutionary theory to psychopathology.
Evolutionary perspective on the origins of psychopathology
Functioning but aversive mechanisms
Psychopathology can result from functioning but aversive psychobiological mechanisms. Fear and anxiety, for example, are aversive, but they are often adaptive—particularly in dangerous environments. In ancestral environments, fear and anxiety protected humans from predators, rivals, status loss, accidents, and many other threats.
Functioning but maladaptive mechanisms
Psychopathology can result from functioning but maladaptive psychobiological mechanisms. Functioning psychobiological mechanisms often become maladaptive when environmental conditions change. Substance use disorders, for example, are partly the result of functioning psychobiological mechanisms that evolved to motivate ancestral humans to pursue the pleasure of consummatory rewards.
Malfunctioning mechanisms
Psychopathology can result from malfunctioning psychobiological mechanisms. Examples of malfunctioning psychobiological mechanisms include neurodevelopmental disorders like intellectual disability and neurocognitive disorders like Alzheimer’s disease.
Anachronistic adaptations
Discrepancies between ancestral and modern environments can result in anachronistic adaptations, i.e. traits or behaviors that were once adaptive but that have become maladaptive as environmental conditions changed. The mismatch between an organism and its environment can result in a wide range of physical and mental health problems.
For example, generalized anxiety may have been adaptive in a high-mortality ancestral environment but it is often maladaptive in a low-mortality modern environment. Similarly, some personality traits and behaviors that were adaptive in childhood may become maladaptive in adulthood as environmental conditions change.
