The Colorful Evidence for Common Descent 1. Anatomy: The Shared Skeleton "Blueprint" Species share similar physical features because they inherited them from a common ancestor—a concept known as homologous structures. Colorful Example: The pentadactyl limb. A human arm, a dog leg, a bird wing, and a whale flipper all share the same basic bone structure (humerus, radius, ulna, carpals), despite performing very different functions.Picture: A colorful, labeled diagram showing the same bone structu