One web site defines Evolutionary Psychology (EP) in this way:
"Evolutionary psychology is the science that seeks to explain through universal mechanisms of behavior why humans act the way they do…Evolutionary psychology seeks to reconstruct problems that our ancestors faced in their primitive environments, and the problem-solving mechanisms they created to meet those particular challenges. From these reconstructed problem-solving adaptations, the science then attempts to establish the common roots of our ancestral behavior, and how those common behavioral roots are manifested today in the widely scattered cultures of the planet. The goal is to understand human behavior that is universally aimed at the passing of one's genes into the next generation."
One simple example: humans seem to have an innate fear of snakes. The fear is not universal but it is felt by many humans. Such a fear is easy to explain from human evolutionary history.
EP can help to explain why mothers love their children, why step-children are often not as well-loved as biological children, etc.
Some scientists use EP to attempt to explain why people tend to be religious. The explanations run along these lines:
When the human intellect reached the point that they could explain some things about the natural world, they started to feel uneasy about those things that they could not explain. They developed the idea of a supernatural being – a God – to help explain those things. For example, early humans could not explain what caused rain. The solution: a rain god.
Not all scientists embrace EP. While it certainly explains some things, in many cases it’s difficult to develop a testable and potentially falsifiable test for the ideas.
Example: how do you test the idea that religion is explained as I describe it above?
Another problem is that EP may try to explain too much.
For example, I found an article by some authors named Alford, Funk and Hibbing titled "Are Politically Orientations Genetically Transmitted?" It claims that genes count for more than environment when forming political ideologies.
If you voted for Barack Obama in the 2008 Presidential election, your genes helped convince you do so.
In my view, this is "over-reaching".
Moreover, how do you really test such a hypothesis? The authors of the paper use attitudes of monozygotic (identical twins raised separately) compared to dizygotic twins (children with different parents but nearly identical ages raised together). Monozygotic twins tended to share a higher percentage of political views than dizygotic twins did.
But it turns out that the correlation varies quite a bit when they compared various specific political views. The correlation on property taxes was higher than the correlation on gay marriage. Surprisingly the correlation on party affiliation was lowest of all (only 0.14).
It seems to me that political views – if there is really any correlation at all – are really just a secondary characteristic. Identical twins are similarly intelligent, for example, and intelligence can be correlated with political views. Also physical attractiveness is influenced by genetics and such attractiveness influences the personality of individuals which, in turn, affects their views on some political issues.
There is a real danger in such studies about EP. That danger is that "evolutionary psychology" has some similarities to Social Darwinism – the idea that the character of people is determined by their genes. The implications of Social Darwinism include eugenics – discouraging people from reproducing who have perceived bad characteristics.
While the EP examples I've seen so far generally relate to humans as a complete species - a fear of snakes is shared by nearly all humans, for example, independent of their race or culture – if political views are influenced by our genes, maybe your honesty or your willingness to work hard is as well.
It's worth talking about such things, but there is also danger.
 http://www.evoyage.com/Whatis.html, referenced on May 28, 2009
 http://www.apsanet.org/imgtest/GeneticsAPSR0505.pdf, referenced on May 28, 2009