Georgia Southern University Professor Published in Nature

March 19, 2009

A paper published in this week’s edition of the scientific journal Nature by a Georgia Southern University faculty member helps lay the foundation for explaining how whales evolved from land animals around 55 million years ago.

Research by Jonathan H. Geisler Ph.D., associate professor of Geology and Curator of Paleontology at Georgia Southern University, and his co-author Jessica Theodor Ph.D. (University of Calgary) suggests that the closest living animal to whales and dolphins is the hippopotamus. The fossil record of hippos is relatively short, so they have pinpointed the fossil Indohyus, from Pakistan, as close to the ancient split between hippos and whales. Although previous work by Geisler and others had recognized close relationships among Indohyus, hippos, and whales, the current study resolves their exact evolutionary positions. Knowing this, Geisler and Theodor have been able to develop a hypothesis on how the ancestors of whales went from living on land to having descendants that lived underwater.

‘The ancestor of whales went through a hippo-like stage where they were amphibious, walked on river bottoms instead of swam, and ventured onto land to forage for plants,” said Geisler. ‘Then they went through an Indohyus-like stage where they spent nearly all of their time in the water, possibly feeding on aquatic vegetation. Later, their teeth evolved for fish eating and the earliest whales lost their ability to move on land.” Geisler says this scenario can be tested and further refined by studies that incorporate data from living and extinct species.