Individual differences as the output of evolved calibration mechanisms: does the theory make sense in view of empirical observations?

Evolutionary psychologists have traditionally focussed on understanding the evolutionary basis of species-typical or sex-typical behavioural features. Recently, though, the differences between individuals have received increasing attention. A major class of evolutionary explanations of individual differences views them as the output of specialised species-typical calibration mechanisms that evolved to optimise the level of a trait to relevant contextual factors, which may be other characteristics of the individual or aspects of their environment. In this article I describe recent evidence that casts doubt on evolved calibration hypotheses of two particular traits. - facial masculinity preference and the personality dimension extraversion. I then question whether evolved calibration mechanisms fit with what we know about the genetic and environmental causes of complex behavioural variation in general