In Geoff Miller's terminology, there are two Darwinian processes. Natural selection determines whether you live or die; sexual selection determines whether you can impress a mate sufficiently to produce offspring. Both tests need passing to leave descendants.
A female will have most descendants if she mates with a male with a good genetic set of cards (and conversely of course). In humans, it's normally the case that males present themselves to a female and then she gets to decide.
The decision process works better if there are fitness indicators: traits of appearance and/or behaviour which are reliably correlated with an underlying good-quality set of genes. As there are a number of different ways to excel in human societies, fitness indicators could include athletic prowess, firm leadership, intellectual sparkle, superior moral character and so on.
Miller believes that many aspects of the human mind, including intelligence, language and pleasant personality are best understood as proxies for underlying genetic fitness (and thereby sexually-selected), rather than survivalist adaptations. The book has had a big impact.
- Forty reviews on Amazon.com
- Thirteen detailed reviews of the book
- A precis of the entire book has been produced.
My reservations are as follows.
1. Reading this large book is like eating high-quality muesli. There are a few drab and repetitive parts but on a regular basis one come across delicious nuggets of genuine insight and depth. The problem is the lack of an overarching structure, so at the end one finds oneself asking - what exactly does this all amount to?
2. As we're talking about humans here, we have to note that many psychological traits differ quite markedly between different human races, based on their adaptations to significantly different ecologies over the last 40,000 years. Talking about women being able to raise children without the active involvement of men thereby freeing the men up for elective sexual displays of hunting prowess, for example, works for equatorial latitudes where women may gather fruits and berries all the year round. But hunting is not so elective in highly-seasonal environments where little can be gathered in the snowy winter. I know Miller doesn't want to go there, but the result is sloppy reasoning.
3. Many sciences are somewhat reflexive: physicists and chemists are constructed from the same quantum and chemical processes that they describe; economists propose macroeconomic policies whose success depends upon people behaving as modelled, not trying in an informed way to game the policies. However, in evolutionary psychology one can directly predict just why people will be so hostile to the underlying results which the science unfortunately keeps unearthing. Evolutionary psychology, done honestly, just keeps turning up non-PC results.
Miller discusses this quite openly on pages 420 ff. "Creative Ideologies vs. Reliable Knowledge". There seems little biological payoff for generating theories which seem to violate most people's value systems (to give a crass example, many people still feel uncomfortable with the statement that not everyone is of the same intelligence). I think this is a real problem for evolutionary psychology as history tells us that, in practice, scientists are under enormous, career-terminating pressure not to violate conventional mores in their research, even when those mores state that the psychological earth is in fact flat.
Miller has continued his research on sexual selection (there's a recent book Spent: Sex, Evolution, and Consumer Behavior and another in the works for 2011). The ideas feel right and one can only hope we don't have to wait another century for evolutionary psychologists to turn these compelling intuitions and speculations into testable mathematical theories.