The Evolution of Whales

The Evolution of Whales

Image sitting on the beach one July morning. The sun is beaming down and decide to go for a swim. As you approach the water, you see a whale unusually close. You begin to get nervous as it continues to approach the shore. However, you aren’t worried because you know that they are confined to the sea. As the whale comes near you can see it clearly. Just as you think that it will turn around, the whale walks out of the ocean!

If you were to live during the tertiary period, this would be one of the things you would often see. All of the mammals that existed during that time period were terrestrial. They all were land dwelling mammals. Before J. G. M. Thewissen and colleagues’ discovery in Pakistan, many scientists believed, since the constant new discoveries twenty years ago, in what the numerous fossils from North America, Pakistan, and Egypt have revealed, “…these early cetaceans had mobile elbows and external hind limbs with articulated knees. However, they were fully aquatic, except for Ambulocetus, which was amphibious-much like sea lions” (Walking with Whales).

Scientists had some idea to the evolutionary process of whales. “It has always been clear that aquatic cetaceans must have evolved from terrestrial mammals and returned to the water, and the forelimbs of recent cetaceans still have the same general pattern as that of land mammals.” (Walking with Whales) It was known fact that land mammals and whales were related. However, the change from ancient whales to modern whales is drastic.

Today, we see much less of an obvious relationship of the cetaceans to the terrestrial mammals.

“…Modern cetaceans are highly specialized, with numerous adaptations that allow them t...

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J. G. M. Thewissen and his colleagues changed the way in which scientists thought about the early lifestyles of whales. The evolution of the ancient artiodactyls was discovered to be joined with the well-known group of cetaceans. The tertiary period was a time of terrestrial life forms. Every mammal walked the earth. It wasn’t uncommon to see a whale running through the grasslands or shark sleeping on the coast of a land mass. It was a time when mammals roamed freely and unconfined by the limits of the ocean. Now that scientists have this newly found knowledge, it is time the scientists further investigate “why?”

Works Cited

Muizon, Christian De. Walking With Whales. Nature 413, 259-260. September 2001.

www.nature.com/nature/journal/v413/n6853

Thewessen, J. G. M., Williams, E. M., Roe, L. J. & Hussain, S. T. Nature 413, 277-281.

2001.