Researchers have puzzled over the “missing heritability” problem for quantitative traits, including personality dimensions such as the Big Five. Specifically, although all human personality traits exhibit substantial additive genetic variance, large gene association studies with immense statistical power have failed to discover specific genes that explain even a fraction of this estimated heritability (e.g., Service, Verweij, Lahti, Congdon, et al., 2012). Because such effects are prerequisite for the maintenance of personality differences via fluctuating (including frequency-dependent) selection on specific polymorphic genotypes, this initially promising type of evolutionary genetic model would seem to be rendered untenable by the empirical data as an explanation for the heritability of personality (Lukaszewski & von Rueden, 2015; Verweij et al., 2012). Recently, Lukaszewski and Roney (2011) hypothesized that part of extraversion's genetic variance reflects its facultative calibration to highly heritable, condition-dependent phenotypic features that would have predicted the cost–benefit ratio of extraverted strategies across ancestral environments. Specifically, we predicted that extraversion would have been a more beneficial strategy on average for more physically attractive and stronger individuals. If strength and attractiveness are in turn heritable due to genetic effects on condition — for instance, individuals with lower mutation loads develop both stronger and more attractive phenotypes — then extraversion would be heritable even if no specific genes directly encode for it. Such “reactive heritability” (see Tooby & Cosmides, 1990), if confirmed, could provide both a partial explanation for themissing heritability problem and a functional explanation for why individuals differ in extraversion. In prima facie support of the reactive heritability hypothesis, multiple empirical studies have found that measures of physical strength and attractiveness, respectively, positively predict individual differences in extraversion and related interpersonal dimensions (for a review of these findings, see Lukaszewski & Roney, 2011; Lukaszewski & von Rueden, 2015). As such, we have advocated for quantitative genetic studies to provide a proper test of extraversion's reactive heritability. In the current issue of Evolution and Human Behavior, Haysom et al. (2015) report a quantitative genetic test of the hypothesis that extraversion exhibits reactive heritability in relation to conditiondependent phenotypic features. Using a classical twin study design, they tested for phenotypic and genetic correlations of extraversion with other-rated facial attractiveness (from headshot photos), body mass index (BMI), height (as a proxy for strength) and intelligence test scores. Overall, results were not very supportive of the reactive heritability hypothesis: Of the phenotypic features examined, only facial attractiveness exhibited the predicted positive association with extraversion, and this effect explained at most a few percent of extraversion's additive genetic variance. Haysom et al. concluded that their findings cast some doubt on the viability of the reactive heritability hypothesis of extraversion. We do not entirely disagree. This was in some ways the most sophisticated test of the reactive heritability hypothesis ever conducted, and it appears to indicate that putative measures of condition-dependent phenotypic features collectively explain very little of the heritable variance in extraversion. At the very least, then, this study reports empirical patterns that must be accounted for. However, we believe that theHaysomet al. study is inconclusive as a falsification of the reactive heritability hypothesis in light of several substantive (but understandable) limitations. Most importantly, the operational definitions of condition-dependent features employed in this study do not compellingly tap the most theoretically relevant aspects of strength, intelligence, and attractiveness: