I have heard that whales evolved millions of years ago into their present form, including their very large brains. We humans must be relatively recent in terms of our brain structures. Are there data concerning evolutionary development in whales?

Matthew Kabrisky
Dayton, Ohio

“Learning to Listen: How some vertebrates evolved biological sonar” (SN: 5/14/05, p. 314) reviews the evolutionary steps in echolocation development in whales. —Sid Perkins