But we know for certain that this back-to-the-water evolution did occur ... be side branches of the family tree. But the important thing is that each fossil whale shares new, whale-like features ...

This is the evolutionary tree of sperm whales, showing the relationships of extinct and living species, and when reduction of the spermaceti organ took place. Disclaimer: AAAS and EurekAlert!

Nearly a century later George Gaylord Simpson, the preeminent paleontologist of the 20th century, was still at a loss to explain where whales fit in his otherwise orderly evolutionary tree of mammals.

Looking deeper by mapping the skull markers onto the cetacean phylogenetic tree, she and a team of fellow whale experts and evolutionary modelers could infer when particular changes in structure had ...

How Pakicetus' descendants evolved into whales is one of the most intriguing evolutionary journeys known to science. What did the first whales look like? Pakicetus (pictured above) looked nothing like ...

Discover the evolutionary secrets of some of the world’s most majestic creatures. From voracious crocodiles and acrobatic birds to stupendous whales and majestic elephants, When Whales Walked ...