Evolutionary psychologists approach the human mind as an archive of all the psychological tendencies that helped our hunter-gatherer ancestors survive and reproduce, said experts on the second day of the 2004 University of British Columbia Mind, Culture and Evolution conference. As a result, evolutionary psychologists are particularly interested in those thoughts, feelings and behaviors that have to do with fighting, fleeing and mating.

  • Murderous males. Evolutionary theory predicts that the grimmer a male's prospects for reproduction, the fiercer he will fight for the resources he needs to secure a mate, related evolutionary psychologists Margo Wilson, PhD, and Martin Daly, PhD, of McMaster University in Hamilton, Ontario, Canada. In places where the gap between rich and poor is greatest, they reasoned, the violence should be even more intense, since poorer men can see that at least some people have ample resources and that maybe, with a little push-and-shove, they could too. Across several studies comparing neighborhoods, states/provinces and nations, Wilson and Daly have found that, indeed, an area's income inequality predicts that area's homicide rates.

  • Depression as adaptation. Most researchers agree that biological and situational factors contribute to depression, said University of Michigan psychiatrist Randolph Nesse, MD. What researchers know less about, he said, is which situations lead to it, and why people have the biological potential for depression in the first place.

Nesse suggested that the most depressing situations are those involving the pursuit of hopeless goals. He also argued that, biologically speaking, low mood may be nature's way of making people give up on unproductive goals before pursuing them becomes too costly. Combining these ideas, Nesse argued that depression sets in "when people cannot disengage from their unreachable goals," either because those goals are too important to the person or because the situation is objectively inescapable.

  • Miffed mates. Men and women have always faced competing goals when it comes to shepherding their genes into the next generation, said evolutionary psychologist David Buss, PhD, of the University of Texas: Women pass on more of their genes when men commit to investing in their slow-maturing offspring. Although men often do make this commitment, they also have a compelling plan B: skip the commitment part and procreate with many women. Evidence for men and women's divergent mating goals, said Buss, can be found in men and women's divergent relationship complaints. For example, analyzing Americans' and Germans' questionnaire responses, Buss and University of California, Los Angeles, psychologist Martie Haselton, PhD, showed that women get most annoyed when men falsely promise commitment in order to get sex, while men get most annoyed when women falsely promise sex in order to get commitment.