Birds and humans are theorized to have a common ancestor because they have homologous structures.

Question

Which evidence best supports this theory?

1.They both have tails as embryos.
2.They each have vestigial structures.
3.They have analogous structures.
4.They have different forms as adults.

Answer 1

The evidence that best supports the theory that birds and humans have a common ancestor due to homologous structures is:

1. They both have tails as embryos.

This point indicates that both species share developmental features during embryonic stages, which suggests a common ancestor. Homologous structures are those that arise from a common evolutionary origin, even if they may serve different functions in the adult forms. The presence of tails in the embryonic development of both birds and humans supports the idea of shared ancestry.

In contrast, vestigial structures (option 2) suggest evolutionary history but do not specifically indicate common anatomy, while analogous structures (option 3) indicate convergent evolution rather than common ancestry. Option 4 simply states that they have different adult forms without addressing their evolutionary relationship.