Phillip D. Gingerich, a well known Paleontologoist, is known for his work on the ancestory of whales. Due to his research a lot of important conclusions have been made pertaining to the evolution of whales and how they have become what we know them as today. So why whales? You may ask. The evolution of whales has aways been a mystery to scientists. How did a large, air-breathing, warm-blooded, big brained mammal come to live only in water when mammals evolved on land?
Since the 1970's Gingerich has been collecting whale fossils from remote digs in Egypt and Pakistan. He discovered Pakicetus, a terrestrial mammal who dates back to 50 million years ago. The significance of Pakicetus was that the ear bones reflect its membership in the whale lineage but whose skull looks dog like. Ambulocetus natans or "walking-and-swimming whale" was also a recent discovery that was a whale form but with webbed feet, legs suitable for either walking or swimming, and a long toothy snout. Gingerich and his co-workers found several more including Rodhocetus balochistanesis which was a complete sea creature with flipper like legs, and nostrils that shifted backward, halfway to the blow hole on a modern whale. The pieces began to fall into place. Gingerich's goal was to confirm the relationship between whales and a group of carnivorous Eocene mammals known as Mesonychids that Ginerich believed whales descended from.
However, Molecular biologists had come to a different conclusion. DNA hybridization and other tests suggested that whales had descended from even-toed herbivores such as hippos, called artiodactyls. Another discovery of an ankle fossil brought Gingerich on the side of the Molecular biologists. He realized how closely related whales are to antelopes. Like the first animals that crawled out of the sea and onto land, the whales did just the opposite. They slowly adapted to being a mammal-who births young, breaths air, and is warm-blooded and lives in the ocean. They lost their legs and became adapted to a marine existence. Whale evolution may not seem important, but it has been able to tell us a lot about evolution in general and about how the world around us has come about.
According to the BBC, whales evolved from land animals who gradually lost their limbs, until they became fully adapted for under water life. One major similarity between land animals and whales is the semi circular ear canal system which regulates an animal's balance. For whales, this inner ear canal is much smaller than that of a land animals. For whales, the size of ear canals adapted very quickly so they wouldn't get dizzy while swimming. Whales didn't become fully water animals until 40 to 45 million years ago.
[[image http://evolution.berkeley.edu/evosite/evo101/images/whaleancestors.gi
I got my outside source from:
http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html
