Depression Is an Adaptation

Longley, Alison J.

doi:10.1001/archpsyc.58.11.1083

Cited by 4 publications

(3 citation statements)

References 3 publications

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“…For example, mental disorders which look harmful and dysfunctional, and which show below-average fitness under some conditions, might show above-average fitness under other conditions. This type of selection, known as balancing selection, has been one of the most popular ideas among evolutionary thinkers for resolving the paradox of common, harmful, heritable mental disorders (Allen & Sarich 1988;Barrantes-Vidal 2004;Karlsson 1974;Longley 2001;Mealey 1995;Stevens & Price 2000a), with some researchers even implying that balancing selection is the only possible resolution to the paradox (D. R. Wilson 1998). One purpose of this article is to rebut such claims by showing that there are at least two other potential resolutions to the paradox: neutral evolution and mutation-selection balance.…”

Section: Can Balancing Selection Explain Common Harmful Heritable Mmentioning

confidence: 99%

Resolving the paradox of common, harmful, heritable mental disorders: Which evolutionary genetic models work best?

2006

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Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior.

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Section: Can Balancing Selection Explain Common Harmful Heritable Mmentioning

confidence: 99%

Resolving the paradox of common, harmful, heritable mental disorders: Which evolutionary genetic models work best?

2006

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“…The predominant view on the prevalence of psychological disorders among evolutionary psychiatrists and evolutionary psychologists is the balancing selection model ( Barrantes-Vidal 2004;Longley 2001;Wilson 1998). In this model, alleles that predispose an individual towards a disorder in certain instances may increase fitness.…”

Section: Evolutionary Models Balancing Selectionmentioning

confidence: 99%

Understanding the Prevalence of Sexual Dysfunctions in Women: an Evolutionary Perspective

Apostolou

2015

Adaptive Human Behavior and Physiology

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Epidemiological studies indicate that almost one in two women face some kind of sexual dysfunction. Given the importance of sexual functioning for successful reproduction, such a high prevalence is enigmatic. Selection forces should have reduced to a low frequency, or have eliminated completely from the gene pool, any alleles that predispose for sexual dysfunctions. Epidemiological studies indicate that this did not happen, and the present paper attempts to examine the reasons why. Based on anthropological and historical evidence, it is argued that in ancestral societies sexual motivation was a much weaker predictor of successful mating in women, than it is today in post-industrial societies. Accordingly, balancing selection has favored a female type of sexual behavior which is characterized by low sexual motivation. This low level of sexual motivation is not optimal in post-industrial societies where mate choice is not regulated, resulting in women, who have such predispositions, to be classified as suffering from a dysfunction. Predictions are derived from the proposed model, and matched with available evidence.

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“…The predominant view on the prevalence of psychological disorders among evolutionary psychiatrists and evolutionary psychologists is the balancing selection model (Barrantes-Vidal 2004;Longley 2001;Wilson 1998). In the frequency-dependent selection aspect of the model, the fitness of alleles which predispose for a dysfunction increases as they become rarer.…”

Section: Evolutionary Models Balancing Selectionmentioning

confidence: 99%

Sexual Dysfunctions in Men: An Evolutionary Perspective

Apostolou

2015

Evolutionary Psychological Science

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Successful sexual intercourse is a prerequisite for successful reproduction, a fact that translates into strong evolutionary pressures being exercised on mechanisms that regulate sexual functioning to work optimally. In effect, selection forces would remove from the gene pool any alleles that predispose for sexual dysfunctions, limiting their prevalence to very low levels. But this did not happen with epidemiological studies indicating that sexual dysfunctions are common, with approximately one in three men facing such a difficulty. This raises the question why evolutionary forces have allowed such variation in sexual functioning given its importance in reproduction. The present paper attempts to address this question by applying three evolutionary models on anthropological and historical evidence that depicts the ancestral human condition. It is argued that the high prevalence of sexual dysfunctions in men is predominantly explained by the mismatch between ancestral and modern environments, with selection forces not having sufficient time to optimize sexual functioning mechanisms to the demands of modern conditions. The proposed evolutionary framework is employed to derive predictions which are examined against the available evidence on sexual dysfunctions.

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Depression Is an Adaptation

Cited by 4 publications

References 3 publications

Resolving the paradox of common, harmful, heritable mental disorders: Which evolutionary genetic models work best?

Resolving the paradox of common, harmful, heritable mental disorders: Which evolutionary genetic models work best?

Understanding the Prevalence of Sexual Dysfunctions in Women: an Evolutionary Perspective

Sexual Dysfunctions in Men: An Evolutionary Perspective

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