The Extraversion Continuum in Evolutionary Perspective: A Review of Recent Theory and Evidence




We review research on the ultimate and proximate origins of variation along the extraversion continuum. After describing the cost-benefit tradeoffs that may have maintained variation in extraversion over human evolution, we consider the evidence bearing on multiple distinct evolutionary hypotheses regarding the causal underpinnings of such variation. On the basis of the reviewed evidence, we argue that fluctuating selection on specific polymorphic genotypes is unlikely to explain the origins of individual differences in extraversion. Rather, adaptively patterned variation in extraversion is likely orchestrated primarily by facultative adaptations designed to calibrate behavioral strategies to cues available in ontogeny. For example, emerging research supports the hypothesis that extraversion may be “reactively heritable” by virtue of its calibration to heritable condition-dependent phenotypic features – which in turn helps explain extraversion’s genetic variance, as well as its consistent positive association with reproductive success. Finally, evidence suggests that some of the inter-individual variance in extraversion is fundamentally noisy, arising as a side effect of mutation–selection balance or pleiotropic polymorphisms maintained via pathogen–host coevolution. If correct, these conclusions indicate that future research should focus on elucidating the facultative adaptations designed to regulate the production of behaviors falling on the extraversion continuum.

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Refer to Dr. Christopher von Rueden's website for further information.

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Copyright © 2016 Elsevier B.V. This article first appeared in Personality and Individual Differences 77 (2015), 186-192.