bio

Homologous structures

Features that are similar because they were inherited from a shared ancestor, even when later put to very different uses - like the human arm, the whale's flipper and the bat's wing, all built from the same tetrapod forelimb bones in the same order. Homology is the signature of kinship; it stands opposite to analogy, which is the signature of convergence. Telling the two apart is the heart of reading an organism's history.