Evolution of Personality: Environmental Variation
In last week’s blog post, I addressed the evolutionary genetics of personality and the genetic contributions to variation in personality traits. In this post, I would like to examine a different phenomenon, namely how the same genes can lead to different non-random variation in personality. If we want to understand how traits work as motivations, we need to understand how they evolved. Let’s briefly review some very simple models of how variation can link to genetics. In one model, variation in personality is due simply to people having different combinations of genes: People with gene A tend to be extroverts, while people with gene B tend to be introverts. This kind of model could represent what biologists call an obligate adaptation (a gene causes a trait in a fixed manner). However, people with the same genes may develop very different personalities if they are put in the same environment, through what is referred to as facultative adaptations (genes create mechanisms which develop in different ways in different environments, or different genes are turned on in different environments). Facultative adaptations are like “if-then” rules, as everyone tends to have the same genes; but if they develop in one environment, they create one characteristic (say, extraversion), and if they develop in another environment, they lead to another characteristic (say, introversion).