Emory Valley lies on the eastern edge of the city, and the Clinch River runs through it. It's a beautiful spot to sit and study the world - so let's do that. Here's the Emory Valley Center for Evolutionary Studies...
You want your transitional fossils? Well, they don't come any better than this. Archaeopteryx has competiton: Tiktaalik, the recently discovered fish that walked like a critter.A new fish-like tetrapod has been found in the 375 million year old Devon rocks of the Canadian Arctic.
The 3 metre-long new species, Tiktaalik roseae, had a flattened, crocodile-like head and strong, bony leg-like fins. Ellesmere Island is more than 970 kilometers north of the Arctic Circle in Canada's Nunavut territory.
The creature is being hailed as a crucial missing link between fish and land animals—including the prehistoric ancestors of humans. The fish shows other features characteristic of land animals, including ribs, a neck, and nostrils on its snout for breathing air.
Researchers say the fish shows how fins on freshwater species first began transforming into limbs some 380 million years ago. The change was a huge evolutionary step that opened the way for vertebrates—animals with backbones—to emerge from the water.
The discovery marked the culmination of a five-year, 650 kilometer fossil hunt across the Arctic's frozen tundra.
Illustration by Shawn Gould
© National Geographic Society
Tiktaalik had fins, but they aren't your standard fins. "In the fishes' forward fins, the scientists found evidence of limbs in the making. There are the beginnings of digits, proto-wrists, elbows and shoulders." (NYT) Tiktaalik's head and ribs also show signs of tetrapod nature (tetrapod = four-legged). Thus, Tiktaalik is a transitional fossil between fish and land animals.
Transitional - or intermediate - fossils are the lucky finds (lucky when you consider how unlikely it is that any animal becomes a fossil) that document what evolutionary theory says happened, when one form changes (over long years) to another. IDers and Creationists claim there aren't any, or there aren't enough.
But, as Michael J. Novacek, a paleontologist at the American Museum of Natural History in Manhattan, who was not involved in the research, said: "A good fossil cuts through a lot of scientific argument."
And Tiktaalik is important for more than just being a transitional fossil. As Nature says in its article:First, it demonstrates the predictive capacity of palaeontology. The Nunavut field project had the express aim of finding an intermediate between Panderichthys and tetrapods, by searching in sediments from the most probable environment (rivers) and time (early Late Devonian). Second, Tiktaalik adds enormously to our understanding of the fish-tetrapod transition because of its position on the tree and the combination of characters it displays. [emphasis mine-k]Predictive capacity.
That's what makes it science.
Science makes predictions based on what we know, and then tests those predicitions. If they don't pan out, then we, perhaps reluctantly, make corrections and keep going. But if they do, as here, then the theory is strengthened enormously.
For further reading, here are some articles about Tiktaalik:
Beginning with PZ's (as always) excellent article at Pharyngula
and Carl Zimmer's equally good article at The Loom.
Here's the National Geographic piece,
and here's the Nature article (though note you must buy the article unless you're a subscriber).
And a pretty good wrap-up from The New York Times Science.
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