Evolutionary psychology is a theory of human behavior that incorporates the effects of evolution. As our ancestors confronted problems, they developed ways of solving those problems. Over time, the most successful solutions developed into basic instincts. We no longer need to consciously think about certain behaviors, as they simply “come naturally.” Those behaviors are tempered by input from our culture, family, and individual factors, but the underlying behaviors are instinctual.
At its most basic level, evolutionary psychology explains relatively simply topics. A common example is language acquisition. All humans, assuming normal physical structure, are capable of learning language. At some point in history, early man developed language skills beyond grunting and pointing. The ability to communicate complex thoughts was important for survival, and so language acquisition abilities evolved. Which language or languages are learned depends on the language spoken in the home and neighborhood, demonstrating the importance of cultural input.
More complex evolutionary psychology theories attempt to explain more complicated behaviors. For example, many research studies have shown that we are more likely to fear snakes and spiders than other predatory animals such as lions and tigers. From an evolutionary point of view, this may be due to the fact that snakes and spiders are more difficult to spot. It made sense to our ancestors to look carefully for poisonous creatures before sticking their hands into woodpiles or overgrown brush (still a good idea today!). Over time, that caution became an instinctive human reaction.