The evolutionary fitness of personality traits in a small-scale subsistence society☆
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Fig. 1
The relationship between personality and fitness varies by region. (A) Extraversion and fertility among women; (B) Neuroticism and age at first reproduction among women; (C) Industriousness and age at first reproduction among men. All models control for age, Spanish fluency and schooling. Dashed lines refer to regions that were not significantly different from the baseline level (near town). Statistical models are given in Table S6 , available on the journal's website at www.ehbonline.org, and additional relationships are graphed in Figure S3 , available on the journal's website at www.ehbonline.org.
The relationship between personality and fitness varies by region. (A) Extraversion and fertility among women; (B) Neuroticism and age at first reproduction among women; (C) Industriousness and age at first reproduction among men. All models control for age, Spanish fluency and schooling. Dashed lines refer to regions that were not significantly different from the baseline level (near town). Statistical models are given in Table S6, available on the journal's website at www.ehbonline.org, and additional relationships are graphed in Figure S3, available on the journal's website at www.ehbonline.org.
Abstract
The maintenance of personality variation remains an unexplained puzzle in evolutionary biology. Despite evidence among non-humans that personality variation affects fitness, few data exist to assess the personality–fitness relationship in humans. Among Tsimane forager–horticulturalists (n = 632), we test whether personality traits (assessed using a 43-item Big Five Inventory administered orally in native language) predict fertility, offspring survivorship, age of first reproduction, and other fitness correlates (extramarital affairs, conflicts, social visitation, food production, and several health measures). Among men, several personality factors associate with higher fertility, more time spent producing food and social visitation. Among women, the relationship between personality and fitness varies across regions of Tsimane territory. The only case of an intermediate personality level associated with highest fitness was found for Industriousness in men. We find that personality factors positively associated with fitness do not associate with greater health costs, although greater Extraversion and Openness may lead to more conflicts among men. Factor heritability ranges from 60% for Prosociality and Extraversion to 8% for Neuroticism. We interpret our results in light of evolutionary models that explain maintenance of personality variation, including incomplete directional selection, mutation–selection balance, condition-dependent reaction norms and fluctuating selection based on sex or spatial variability in selection pressures.
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☆Funding was provided by NIH/NIA ( R01AG024119 and R56AG024119 ).
