Which of these is based on what has happened in the past?

• A. Ultimate causes
• B. Proximate causes
• C. Distal causation
• D. Current causes

Answer: (A)

Understanding why a trait exists involves distinguishing past history from present mechanism. Ultimate causes answer the question of why a trait evolved, pointing to historical events and past selective pressures that shaped it. They look at the evolutionary history and explain how past outcomes gave rise to the trait we see today. For example, a behavior that improves reproductive success in ancestors is retained because those individuals left more offspring over generations; that reasoning ties directly to what happened in the past to produce the current trait.

Proximate explanations, by contrast, describe how the trait works right now—the immediate mechanisms like hormones, neural pathways, or developmental processes that trigger the behavior in an organism today. The other terms like current causes aren’t standard for this historical perspective, and distal causation is sometimes used in different contexts, but the clearest past-based explanation in this framing is the ultimate cause.