Recently, there has been a rapidly growing interest in understanding the evolutionary basis of heritable personality variation, both in humans (Bouchard and Loehlin 2001; Nettle 2005, 2006; Penke et al. 2007; Alvergne et al. 2010; Gangestad 2010; Nettle and Penke 2010; Verweij et al. 2010; Buss and Hawley 2011; Lukaszewski and Roney 2011; Del Giudice 2012) and in other animals (Dingemanse et al. 2004; Cote et al. 2008; Bergmuller and Taborsky 2010; Dingemanse and Wolf 2010; Dochtermann and Roff 2010; van Oers and Mueller 2010; Wolf and Weissing 2010). Indeed, the broader line of inquiry is one of the major outstanding questions in evolutionary biology (Mitchell-Olds et al. 2007): how is genetic variation maintained in traits where there is selection for only the most advantageous genotypic trait values?
