Scientists use teeth to analyze evolution of whales walking on land to swimming in ocean Millions of years ago, whales had teeth and walked on land. Now they do not. What happened in between? By: KGTV Staff and last updated 2021-06-15 16:31:10-04 SAN DIEGO, Calif. â The ancestors of whales used to walk on land, and San Diego scientists are working to uncover mysteries about how the evolution from land to sea took place. Theyâre turning to whalesâ teeth to find answers. More than 50 million years ago, whalesâ ancestors walked on land. Now, they still have features that link the land tendencies.