The former is true; as for the latter, such a charge
misunderstands the utility of adaptive explanation in psychology.
The evolutionary framework used here is hypothesis
generating. That is, an article such as this one, which
draws on evolutionary biology, is not an end in itself but
rather an engine for generating testable empirical ideas.
The particular costs and benefits listed here may not turn
out to be the correct ones. However, the framework makes
testable predictions that would not have been arrived at
inductively. For extraversion, the hypothesis that high scorers
will have greater numbers of sexual partners but more
serious injuries has already been confirmed (Nettle, 2005).
For neuroticism, the current framework makes the prediction
that performance on certain types of perceptual monitoring
tasks, such as detecting an artificial predator, will
actually be improved by neuroticism. Because neuroticism
impairs performance on many kinds of tasks, this is a novel
prediction