A Great Site Returns

Posted by Siamang on: 11.13.2006 /

Here’s a science post. Don’t worry, it’s fun!

Olduvai George is the website of Carl Buell. Carl is one of the foremost natural history illustrators working today. The work he does is really wonderful from an artistic standpoint.

His knowlege of animal anatomy using modern animals pays off dividends when he sets out to illustrate animals that we only know from the fossil record.

When drawing an extinct animal, he first needs to get the best information he can on the fossil skeleton of the animal. He plans out his painting with the precise skeletal dimensions of the animal in mind. Then he starts building the animal up from there.

To do this, he relies on two different and very important rules of biology: homology and analogy. We’ll get back to that in a minute.

The difficulty in rendering an animal that hasn’t seen daylight in a few million years is that we have no photographs. So Carl has to start building the animal in his mind. He’s not totally in the dark there, there are two places he can look. First, he can see if the animal has living relatives, and see how they’re constructed. This gives him a good grounding in the anatomy of the animal. If the animal is a transitional form… say from a hippo-like creature to a whale-like creature.. he can study the modern descendents and get some understanding. If he can see how the bones of a modern whale relate to the outward appearance of a whale, he can start to see how his proto-whales might have looked.

The other thing he has working for him is evolutionary relay. Evolutionary relay is when different species evolve similar structures as a result of interaction in their environment. For example, fins. Dolphins are mammals, but they have fins like fish. So does this guy, neither a fish nor a mammal:

Tylosaurus lived during the Upper Cretaceous period, around 65 million years ago, and was not a dinosaur, but rather closely related to snakes and monitor lizards. You can see where Carl has woven in the likeness of both the monitor lizard and the flippers of something resembling a walrus.

Like other aquatic animals, Tylosaurus was adapted for aquatic life, and those adaptations serve Carl well…. he knows which animals to look at to see what carpals and metacarpals do when they become a flipper.

So those are the two rules of homology and analogy. Homology is a feature shared between two animals as a result of common ancestry. For example, you and I are mammals, and we share our mammalian traits with the cats of the world because of a distant relative.

Analogy is when a feature is shared, but for reasons unrelated to ancestry. Features that evolved seperately in different lineages are called analogous. For example, wings in birds, which evolved from the forelimbs of dinosars, are analogous to wings in insects, which may have evolved from gill-like structures in water bugs. Some features are so successful, they have evolved seperately many, many times in the history of life on earth. The eye, for example, may have evolved seperately as many as 40 times.

Using homology and analogy, Carl can bring to life these wonderful creatures for us.

I called this post “A Great Site Returns,” and that’s because Carl hasn’t been posting for awhile. It’s sad and ironic that while Carl brings these wonderful animals to life for us, he lost the life of his beloved dog, Tito. Read his past blog entrys to get to know who Tito was, and how special an animal he was. The loss of Tito was one part of a very complex, difficult time for Carl. But I’m mightly glad he’s back sharing his art with us.

Thanks for coming back, Carl. We appreciate it!

-SIAMANG

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