Is The Hippopotamus The Closest Living Relative To The Whale?

Hippos spend lots of time in the water and now it turns out (or researchers argue), they are the closest living relative to whales. It also turns out, the two are swimming in a bit of controversy.

Jessica Theodor, an associate professor in the Department of Biological Sciences at the University of Calgary, and her colleague Jonathan Geisler, associate professor at Georgia Southern University are disputing a recent study that creates a different family tree for the hippo.

That research was published in Nature in December 2007 by J. G. M. Thewissen, a professor at Northeastern Ohio Universities College of Medicine, and his colleagues. Thewissen says that whales are more closely linked to an extinct pig-like animal, often known as India's pig or Indohyus, while hippos are closely related to living pigs.

But this isn't accurate according to Theodor.

"What Thewissen is saying is that Indohyus is the closest relative of whales - and we agree. Where we think he is wrong, is that he is saying that that hippos are more closely related to true pigs than they are to whales," says Theodor. "This contradicts most of the data from DNA from the last 12 or 13 years. Those data place hippos as the closest living relative to whales."

She says Thewissen did not use DNA evidence, instead used fossil evidence alone to create a family tree and reach the conclusion that hippos have more in common with pigs than whales.

"And the reason their tree is so different is simple: by excluding all the DNA information they left out all the data that shows a strong relationship between whales and hippos."

Theodor's rebuttal of Thewissen's work will appear in Nature on Thursday, March 19.

via Is The Hippopotamus The Closest Living Relative To The Whale?.