Two New Discoveries Answer Big Questions In Evolution Theory
One study produced what biblical literalists have been demanding ever since Darwin — the iconic “missing links.” If species evolve, they ask, with one segueing into another, where are the transition fossils, those man-ape or reptile-mammal creatures that evolution posits?In yesterday’s issue of Nature, paleontologists unveiled an answer: well-preserved fossils of a previously unknown fish that was on its way to evolving into a four-limbed land-dweller. It had a jaw, fins and scales like a fish, but a skull, neck, ribs and pectoral fin like the earliest limbed animals, called tetrapods.
Discovered in 2004 on Canada’s Ellesmere Island by Neil Shubin of the University of Chicago and Ted Daeschler of the Academy of Natural Sciences in Philadelphia, the 375-million-year-old Tiktaalik roseae “blurs the boundary between fish and land animals,” said Prof. Shubin. It “is both fish and tetrapod,” showing how life made the transition to land, evolving four limbs from fins.
Previously known fossils of ancient “lobe-finned fish” also seem poised between fish and tetrapods, with pectoral fins containing precursors of the humerus, radius and ulna of tetrapod armbones. But Tiktaalik (an Inuit word for shallow-water fish) makes a stronger case. Its pectoral fin still has thin, fish-like bones, but also contains the three armbones-to-be as well as a wrist-like structure and a hand-like one. The shoulder and elbow could bend, and the proto-wrist could extend, allowing the fin to support the body and propel it on land. “Tiktaalik shows us the stages in the evolution of the tetrapod body plan,” says Dr. Daeschler.
Tiktaalik is an important discovery, although it’s not the first pre-tetrapod transitional fossil. Nor is it the singular missing link creationists/ID proponents (as if there were a difference) demand. Of course, what is far more likely is a series of fossils like Tiktaalik, rather than a single missing link.
Will the creationists go away now? Not likely.
But creationists, many of whose Web sites declare “there are no transitional forms,” are not easily persuaded. John Morris of the Institute for Creation Research in Santee, Calif., says Tiktaalik “is just a variety of fish. There is still a huge gap [between fish and land-dwellers] that has to be filled.”
Add this find to the massive body of scientific evidence supporting evolution, but don’t expect those pushing intelligent design (nee creationism) to care.
