Looking alike doesn't mean closely related
- The idea
- Predict
- See it
- Why
- Check
The idea
“If two species look alike or do the same job, they must share a recent common ancestor.”
Close relatives often look alike, so resemblance seems like a fair clue. When two lineages face the same problem, though, natural selection can solve it twice.
The short version
The mistake: If two species look alike or do the same job, they must share a recent common ancestor.
What's actually true: Distant relatives facing the same demands can evolve similar traits. Kinship shows in many inherited features, especially DNA.
- Homologous traits are inherited from a common ancestor, like the fur, milk and DNA that bats and mice share.
- Analogous traits look or work alike but arose separately. That's convergent evolution. Under the same demand, like flight, selection can favor similar traits in each.
- One structure can be both. Bird and bat wings use the same forelimb bones from a four-limbed ancestor, but each lineage made its own wing.
On the exam: A trait that suits a way of life can evolve twice. Judge kinship by many inherited features, especially DNA.