Fish out of water

April 07, 2006

Three hundred seventy-five million years ago, your ancestors were hauling themselves around on their pectoral fins, taking advantage of the sort-of wrists they had developed, and swiveling their heads for the first time in vertebrate history, which was a good thing because they were busily scouting out undiscovered real estate, otherwise known as dry land.

Grandma and grandpa now have a name: Tiktaalik roseae. They were of a species of fish that was well on its way to becoming a four-legged air breather; newly found Tiktaalik fossils, from the Canadian Arctic, are described in this week's issue of Nature. Scientists believe this creature was the link between the fishes of the sea and the amphibians and reptiles and birds and, eventually, mammals of the shore. What's important about it is that one of the chief arguments creationists have used against evolution was that this link was missing in the fossil record. It's missing no more.

Predictably, anti-Darwinists have poured a fair amount of know-nothing scorn onto the discovery - just check out the blog on Nature's Web site. But facts are ornery little things, and you can't really wish them away.

Tiktaalik was a big fish, but not the biggest, which may be why it found the land so congenial. If you could cross a sturgeon with a crocodile, you might get something like it, but that's not the way it happened. Tiktaalik was the bridge, the connector, the go-between - the evidence of evolution.

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