What evidence would support that dolphins and whales share a common ancestor?

• A. They Swim the Same Way.
• B. They Have Similar Anatomies.
• C. They Live in the Same Area of the Ocean.
• D. They Eat the Same Food.

Answer: (B)

The main idea is that shared anatomy points to a common ancestor. Dolphins and whales have similar body plans, especially the arrangement of bones in their flippers that matches the forelimbs of other mammals. That kind of structural similarity comes from inheriting a common developmental blueprint, not just from living in the same environment or eating the same food. Fossil evidence also shows a progression from land-dwelling mammals to fully aquatic whales, with the same limb pattern carried along, which strengthens the idea of a shared origin. In contrast, living in the same area or eating similar foods can happen for unrelated species because of where they hunt and what resources are nearby, and swimming style can arise from adapting to life in water rather than from shared ancestry.