In evolutionary psychology - which is a discipline in psychology, and not in evolution - researchers make the assumption that the traits they study are adaptations. And it often makes a lot of sense, as we shall see. It just fits so well with how we can easily imagine what our evolutionary past was like, and how the traits would have affected survival and reproduction (the main components of natural selection). However, as I have cautioned before, while we make this assumption, recall that we may at times fool ourselves, because what makes sense and may seem reasonable to us may in fact not have anything to do with reality. Just always keep it in mind, is all I'm saying.
There was a wonderful article in the Economist a couple of days ago on Darwinism*: Why we are, as we are. It surveys five main points as elucidated by evolutionary psychology.
- Why we strive to get wealthier,
- why we commit crimes,
- why we punish,
- why women and men aren't equal, and
- why we are racist.
- Because the wealthier you are the more sex you get to have,
- because it pays, especially when we can't get any sex in the first place,
- because you don't want to be a cuckold,
- because men and women have different reproductive strategies, and
- because xenophobia strengthens your group and weakens other groups.
On the first point, the (anonymous) author writes
The relative nature of status explains the paradox observed in 1974 by an economist called Richard Easterlin that, while rich people are happier than poor people within a country, average happiness does not increase as that country gets richer. This has been disputed recently. But if it withstands scrutiny it means the free-market argument—that because economic growth makes everybody better off, it does not matter that some are more better off than others—does not stand up, at least if “better off” is measured in terms of happiness. What actually matters, Darwinism suggests, is that a free society allows people to rise through the hierarchy by their own efforts: the American dream, if you like. [My emphasis.]The relative nature of status means that people would rather earn $100,000 while everyone else earns $50,000, than earn $150,000 while everyone else earns $300,000. Thus, if everyone earns ten times more than what they earn today, after an initial bout of euphoria, people will go back to being as happy, or unhappy, as they were before there gigantic raise. I choose to interpret this fact as meaning that happiness is irrelevant in evolution. Natural selection does not favor happiness, as it does not influence survival and reproduction. Wealth is not a means to buy lots of ice-cream, but it is rather a signal that I am sexy. So as long as I am richer/sexier than everyone else, I get more you know what.
Which is why I chose the wrong line of work.
* Biologists never call it 'Darwinism'. Evolutionary theory has come a very long way since Darwin, which some people who use the term are ignorant of.