Evolutionary models in biology are also based on the individual animal. This is where selection acts. I guess the difference with humans, and a feature that I don't think is looked at enough in economics, is the feedback. Individual behaviors are selected by their environment. This environment includes culture.
Culture is the collection of individual beliefs, habits, etc.
Thus selection on the individual changes the culture, which changes the selective forces being exerted on the individual. I see an action by an individual. Then I see another man who does not jump off the bridge. Unfortunately this is the same problem that all sciences face. Economists do use data collected from the observation of human behavior.