The evolution of conscientiousness

For most of Geoffrey Miller’s Spent: Sex, Evolution, and Consumer Behavior, Miller treats the genetic influences on human preferences as relatively static over human history. However, in his discussion of the big-five personality trait of conscientiousness, Miller suggests that high conscientiousness was only selected for after the Neolithic Revolution:

In several respects, conscientiousness is an unusual personality trait. Because hunter-gatherer life did not require as much planning and memory for debts and duties as life in larger-scale societies with more complex divisions of labor, conscientiousness may have evolved to higher average levels only recently, and perhaps to a greater degree in some populations than others. Only with the rise of activities like agriculture and animal herding would our ancestors have needed the sort of anxious obsessiveness and future-mindedness that characterize the highly conscientious. Only in the past ten thousand years did our ancestors prosper by continually asking themselves: Have I plowed enough yet? Did I sow the seeds early enough? Is one of the lambs missing? Did my cousin pay me for those olives? Am I teaching my children the skills they will need in twenty years? Thus were born the sleepless predawn ruminations of the middle-aged conscientious.

Economically, conscientiousness is a positive trait (both individually and in the aggregate). While I would argue that other traits would have also faced selection pressures since the Neolithic Revolution, it is probably easier to build a case for conscientiousness evolving in an economically useful manner than for the other big-five traits.

Miller couched most of his discussion in Spent in terms of the big-five (openness, conscientiousness, agreeableness, stability and extraversion) plus general intelligence (the central six as he calls them). Rob Brooks did similarly in Sex, Genes & Rock ‘n’ Roll. It’s probably not a bad habit to get into, as Miller suggests most of the studies about the heritability of preferences are simply reflections of the central-six. In their favour, the central-six are near statistically independent, apart from a slight correlation between openness and intelligence, and have survived in various forms through several decades of psychological research.

As for the trait I often talk about, time preference or patience, I expect that this is a combination of intelligence and conscientiousness.