March 23, 2009

Hippos and pigs or hippos and whales?

Canadian and U.S. professors are disputing each other's view of the family tree involving hippos, whales and pigs.

Associate Professors Jessica Theodor of the University of Calgary and Jonathan Geisler of Georgia Southern University are disputing a recent study by Professor J.G. Thewissen of Northeastern Ohio University that says 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.

What Thewissen is saying is that Indohyus is the closest relative of whales -- and we agree, said Theodor. Where we think he is wrong, is that he is saying hippos are more closely related to true pigs than they are to whales. 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.

Theodor says Thewissen did not use DNA evidence and 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 complete rebuttal of Thewissen's work appears in the journal Nature.