Convergent Evolution

Time for a confession. Those American Cheetahs I was talking about in the last post? They weren't really cheetahs.

They had a build like a cheetah and probably behaved like cheetahs, but DNA evidence taken fro fossils suggest that they were much more closely related to Mountain Lions.

How does a mountain lion come to look like a cheetah? Through something called convergent evolution.

The theory of convergent evolution basically proposes that given enough time to adapt to their surroundings, a species will exist in the form that best suits its habitat.

If a big, predatory mammal lives in an environment with a bunch of small, fast moving prey, you can bet that you will see a few common changes:

• To deal with getting enough oxygen to conduct a high speed chase, a fast predator needs a giant chest cavity. Huge lungs are needed to take in the air, and a big, strong heart is needed to pump blood throughout the body. Animals with big hearts and lungs will be able to chase down more prey, allowing them to have more offspring with barrel chests. The process continues until you start seeing the deep chest characteristic of greyhounds and cheetahs
• Another thing often associated with a high speed lifestyle, a short, flat face with wide nostrils, also appears in both cheetahs and miracinonyx. This is another adaption for increasing oxygen uptake.

Something interesting about convergent evolution is that it shows there is a general body type that goes best with a lifestyle.

Take two radically different animals- hippos and alligators- that live in the same environment. Due to the need to know what is going on above the waterline, both animals have eyes positioned on top of their heads.
Hippos and crocodiles both have eyes on top of their heads, despite being from two different classes. Courtesy of Paul Williams


Or think about three other groups- seals tuna, and the now extinct ichthyosaurs- Even though mammals, fish and reptiles have little in common, all three of these animals share a bullet shaped body. This is an adaption for swimming, as the shape is perfectly hydrodynamic. Natural selection showing us that there is a "perfect" adaption for a lifestyle.