Adaptation and Natural Selection

Homology and Homoplasy

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The word "homology" appears on page 65. And you've got to know the distinction between homology and homoplasy. Homology means the similarity due to the common ancestor. Homoplasy, on the other hand, means similarity due to convergent evolution, but independent origins. For instance, take the fin and the caudal fin of tuna and of dolphin; they are similar but have independent histories, and their similarity comes from adaptation to similar environments and functions. This is homoplasy. However, the fin of tuna and bonito are similar because of the common ancestor, and that's homology.

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