Evolution is a change in the frequency of genes in a population over time. Evolutionary psychologists try to explain universal behaviors. They study how natural selection has encouraged certain behavior patterns to develop.
Charles Darwin (1809–1882) was a British naturalist who is best known for his contributions to evolutionary theory. Although others had noted that species evolved over time, Darwin first put forward the theory of natural selection to explain the process of evolution.
According to this theory, certain inherited characteristics give an organism a survival or reproductive advantage. Organisms pass on these characteristics more often than they pass on other inherited traits.
Example: The species of primates called mandrills have evolved to have bright blue rear ends, because brightly colored rumps help them attract mates and give them a reproductive advantage. Porcupines evolved to have quills, because quills help them to avoid predators and reproduce. This gives porcupines a survival advantage.