Cognitive Ecology in Humans: The Role of Intelligence in Reproductive Ecology

In the present research, we examined the role of intelligence in reproductive ecology with the hypothesis that intelligence has some characteristics of a slow life-history behavioral trait. We did this by analyzing the associations between intelligence, environmental harshness in childhood (parental investment, family dysfunction and economic poverty), and three fertility-related outcomes: planned and observed age at first reproduction and expected total fertility. Data was collected on a large sample of adults (N=1475). Nonlinear, quadratic relations between harsh environment and intelligence were detected: the highest intellectual abilities were found in participants who lived in conditions of intermediate harshness. Furthermore, intelligence was positively associated with both planned and observed age at first reproduction and negatively with expected total fertility. Finally, the interactions between environment and intelligence in the prediction of these outcomes were found: individuals with a lower intellectual capacity who grew up in families with decreased maternal investment plan to have their first child earlier in their lifetime; on the other hand, lower intellectual capacities interacted with elevated paternal investment to predict higher expected number of children. Obtained results largely support the hypothesis of intelligence as a trait which contributes to a slow life-history dynamics. However, they imply that the relations between intelligence and childhood environment, especially family relations, may be complex. Study findings reveal the fruitfulness of an evolutionary ecological approach to intelligence in contemporary humans.