Evolution has no goal
- The idea
- Predict
- See it
- Why
- Check
The idea
“Evolution keeps making species better, moving them toward the traits they'll need.”
Living things fit their lives so well that evolution looks planned. Looking back, the changes line up like steady progress.
The short version
The mistake: Evolution keeps making species better, moving them toward the traits they'll need.
What's actually true: Selection favors heritable traits that help organisms reproduce now. It has no goal and can reverse when conditions change.
- Natural selection has no plan. Individuals with some heritable traits just leave more offspring than others in the conditions they live in now.
- When conditions change, the traits that pay off can change too. A deep beak helps in dry years and can cost in wet ones, so its allele can rise and then fall.
- Selection can't look ahead. It works only on variation the population already has, so it can't prepare for conditions that haven't come.
- A trait often holds steady when costs balance gains, so bigger or smaller versions no longer leave more offspring. That balance moves when conditions do.
On the exam: Ask what helps organisms reproduce in today's conditions. Selection has no target and can't see ahead.