Proximate and Ultimate Causes

Proximate causes explain the immediate reasons why a biological trait or behavior occurs—such as genetic, neurological, or hormonal factors involved in an organism's response. Ultimate causes, on the other hand, refer to the evolutionary reasons why a trait exists—how it helps the species survive and reproduce over generations. For example, a bird’s urge to build a nest (proximate) might stem from hormonal cues, while the reason nests improve survival chances and reproductive success (ultimate). Both perspectives help us understand the "how" and "why" behind biological traits.