|
We like to think of boundaries as being clear-cut borders, but at least in the biological world they generally turn out to be fuzzy zones of change. The line between land and sea is my own favorite example. Last summer my wife and I would sometimes take our oldest daughter Charlotte to the beach. At the time she was a year old and refused to put her toe in the water. This summer she heads straight in, but only about up to her knees. She runs back out and goes back in, repeating the circuit a few dozen times. Next year, I still expect to see her chin above the water line. In her own tadpoling way, Charlotte is reenacting an evolutionary journey taken many times by her fellow mammals--the evolutionary transition back to the water.
These treks have something profound to say about biological change--how life can start out exquisitely adapted to one world and then eventually become adapted just as exquisitely to an utterly different one. Before creationists began marketing bacterial flagella and other examples of intelligent-design snake oil, they loved to harp on the transition from land to sea. Who could possibly believe the story those evolutionary biologists tell us, of a cow plunging into the sea and becoming a whale? And it was true, at least until the 1980s, that no one had found a fossil of a whale with legs. Then paleontologists working in Pakistan found the fossil of a 45-million year old whale named Ambulocetus that looked in life like a furry crocodile. Then they found a seal-like whale just a bit younger. Then they found tiny legs on a 50-foot long, 40-million year old whale named Basilosaurus. I wrote about these discoveries and others like them in my first book, At the Water's Edge, in 1998. I'm amazed at how the fossils have continued turning up since then. Paleontologists have found goat-like legs on a dog-sized whale that lived 50 million years ago, known as Pakicetus. They've found other whales that may have been even more terrestrial than Pakicetus, and many others that branch off somewhere between Pakicetus and Basilosaurus. In the latest review of fossil whales, the evolutionary tree of these transitional species sports thirty branches.
All these discoveries have apparently made whales unsuitable for creationist rhetoric. Yes, you can still find some pseudo-attacks on the fossils, but you have to look hard. The more visible creationists, the ones who testify at school board meetings and write op-eds for the Wall Street Journal, don't bring up whales these days. The animals apparently no longer serve the cause. It's hard to distract people from evidence when it can kick them in the face.
| |
