Heritability and Fitness Correlates of Personality in the Ache, a Natural-Fertility Population in Paraguay

Abstract

The current study assessed the heritability of personality in a traditional natural-fertility population, the Ache of eastern Paraguay. Self-reports (n = 110) and other-reports (n = 66) on the commonly used Big Five Personality Inventory (i.e., extraversion, agreeableness, conscientiousness, neuroticism, openness) were collected. Self-reports did not support the Five Factor Model developed with Western samples, and did not correlate with other-reports for three of the five measured personality factors. Heritability was assessed using factors that were consistent across self- and other-reports and factors assessed using other-reports that showed reliabilities similar to those found in Western samples. Analyses of these items in combination with a multi-generation pedigree (n = 2,132) revealed heritability estimates similar to those found in most Western samples, although we were not able to separately estimate the influence of the common environment on these traits. We also assessed relations between personality and reproductive success (RS), allowing for a test of several mechanisms that might be maintaining heritable variation in personality. Phenotypic analyses, based largely on other-reports, revealed that extraverted men had higher RS than other men, but no other dimensions of personality predicted RS in either sex. Mothers with more agreeable children had more children, and parents mated assortatively on personality. Of the evolutionary processes proposed to maintain variation in personality, assortative mating, selective neutrality, and temporal variation in selection pressures received the most support. However, the current study does not rule out other processes affecting the evolution and maintenance of individual differences in human personality.

Niche diversity can explain cross-cultural differences in personality structure

“…With such simple rules in place, our model shows how increasing the number of niches in a population environment can reduce the correlations between personality attributes, and in turn increase the number of emergent factors required to explain patterns of behavioral covariance. These simulation results expand the scope of existing cross-cultural studies that focus on explaining variation in personality trait values [13,14,15,16,35], to address broader questions concerning cross-cultural variability in personality structure. In addition, niche diversity potentially offers a consilient way in which to think about disparate descriptors of societal complexity.…”

“…To date, the vast majority of data collected to generate structural models of personality comes from large, modern, industrialized societies. Yet, the five factor structure has failed to replicate when tested within smaller-scale societies [12,13,14], in several low income country samples [15], or across a more inclusive set of natural lexicons [16]. Moreover, while many studies have looked at cultural differences in levels of specific traits (e.g.…”

The extraversion continuum in evolutionary perspective: A review of recent theory and evidence

“…Among men, greater manifest extraversion is consistently positively correlated with reproductive success within both small-scale subsistence societies (Alvergne et al, 2010;Bailey et al, 2013;Gurven et al, 2014) and modern industrialized societies (Berg, Lummaa, Lahdenpera, Rotkirch, & Jokela, 2014;Jokela, 2012). Among women, greater extraversion is less strongly associated with reproductive success within small-scale societies (Alvergne et al, 2010;Bailey et al, 2013;Gurven et al, 2014), but has shown positive association with reproduction in modern societies (Berg et al, 2014;Jokela, 2012).…”

The evolutionary fitness of personality traits in a small-scale subsistence society

“…Among rural Senegalese farmers, extraverted men and women with intermediate levels of neuroticism have more children (Alvergne et al, 2010). Among Ache forager-farmers, extraverted men have more children (Bailey et al, 2013). Both studies, however, have small sample sizes, do not consider potential costs of specific dispositions, nor whether dispositions co-vary with observed fitness-related behavior.…”