Posted on 04/05/2006 10:32:31 AM PDT by PatrickHenry
Paleontologists have discovered fossils of a species that provides the missing evolutionary link between fish and the first animals that walked out of water onto land about 375 million years ago. The newly found species, Tiktaalik roseae, has a skull, a neck, ribs and parts of the limbs that are similar to four-legged animals known as tetrapods, as well as fish-like features such as a primitive jaw, fins and scales.
These fossils, found on Ellesmere Island in Arctic Canada, are the most compelling examples yet of an animal that was at the cusp of the fish-tetrapod transition. The new find is described in two related research articles highlighted on the cover of the April 6, 2006, issue of Nature.
"Tiktaalik blurs the boundary between fish and land-living animal both in terms of its anatomy and its way of life," said Neil Shubin, professor and chairman of organismal biology at the University of Chicago and co-leader of the project.
Tiktaalik was a predator with sharp teeth, a crocodile-like head and a flattened body. The well-preserved skeletal material from several specimens, ranging from 4 to 9 feet long, enabled the researchers to study the mosaic pattern of evolutionary change in different parts of the skeleton as fish evolved into land animals.
The high quality of the fossils also allowed the team to examine the joint surfaces on many of the fin bones, concluding that the shoulder, elbow and wrist joints were capable of supporting the body-like limbed animals.
"Human comprehension of the history of life on Earth is taking a major leap forward," said H. Richard Lane, director of sedimentary geology and paleobiology at the National Science Foundation. "These exciting discoveries are providing fossil 'Rosetta Stones' for a deeper understanding of this evolutionary milestone--fish to land-roaming tetrapods."
One of the most important aspects of this discovery is the illumination of the fin-to-limb transition. In a second paper in the journal, the scientists describe in depth how the pectoral fin of the fish serves as the origin of the tetrapod limb.
Embedded in the fin of Tiktaalik are bones that compare to the upper arm, forearm and primitive parts of the hand of land-living animals.
"Most of the major joints of the fin are functional in this fish," Shubin said. "The shoulder, elbow and even parts of the wrist are already there and working in ways similar to the earliest land-living animals."
At the time that Tiktaalik lived, what is now the Canadian Arctic region was part of a landmass that straddled the equator. It had a subtropical climate, much like the Amazon basin today. The species lived in the small streams of this delta system. According to Shubin, the ecological setting in which these animals evolved provided an environment conducive to the transition to life on land.
"We knew that the rocks on Ellesmere Island offered a glimpse into the right time period and the right ancient environments to provide the potential for finding fossils documenting this important evolutionary transition," said Ted Daeschler of the Academy of Natural Sciences in Philadelphia, a co-leader of the project. "Finding the fossils within this remote, rugged terrain, however, required a lot of time and effort."
The nature of the deposits where the fossils were found and the skeletal structure of Tiktaalik suggests the animal lived in shallow water and perhaps even out of the water for short periods.
"The skeleton of Tiktaalik indicates that it could support its body under the force of gravity whether in very shallow water or on land," said Farish Jenkins, professor of organismic and evolutionary biology at Harvard University and co-author of the papers. "This represents a critical early phase in the evolution of all limbed animals, including humans--albeit a very ancient step."
The new fossils were collected during four summers of exploration in Canada's Nunavut Territory, 600 miles from the North Pole, by paleontologists from the Academy of Natural Sciences in Philadelphia, the University of Chicago and Harvard University. Although the team has amassed a diverse assemblage of fossil fish, Shubin said, the discovery of these transitional fossils in 2004 was a vindication of their persistence.
The scientists asked the Nunavut people to propose a formal scientific name for the new species. The Elders Council of Nunavut, the Inuit Qaujimajatuqangit, suggested "Tiktaalik" (tic-TAH-lick)--the word in the Inuktikuk language for "a large, shallow water fish."
The scientists worked through the Department of Culture, Language, Elders and Youth in Nunavut to collaborate with the local Inuit communities. All fossils are the property of the people of Nunavut and will be returned to Canada after they are studied.
The team depended on the maps of the Geological Survey of Canada. The researchers received permits from the Department of Culture, Language, Elders and Youth of the Government of Nunavut, and logistical support in the form of helicopters and bush planes from Polar Continental Shelf Project of Natural Resources Canada. The National Science Foundation and the National Geographic Society, along with an anonymous donor, also helped fund the project.
I I think I meant that the strength of their opinions is inversely proportional to the amount they know.
Flamebait: philosophy is to science what astrology is to astronomy and what alchemy is to chemistry.
*Ahem* I hate to be the one to break this to you, but the entire Bible is mythology (of a sort), in that it describes a belief system, not a scientific construct.
There are many belief systems (Shino, Hindu, Buddhism, etc.). There is certainly a lot of room for philosophical discussion. But none for science.
If you're trying to be contradictory it would be more effective if you said you didn't come from an ape. Apes evolved from monkeys. We evolved from apes.
Thanks furball! The tiger salamander isn't what was the subject of the recent documentary I saw, but interesting nonetheless. This was some sub-saharan creature totally dependent upon water, or lack thereof. If it is a dry year, the creature lays eggs that turn into an amphibious animal. In a wet year it lays eggs that turn into an acquatic animal. I think this was on Discovery or Animal Planet. I'll see if I can find it. It's interesting because drought could render this species extinct but somehow it adapts to either wet or drought conditions during egg laying. So how do it know?? Maybe if it rolls snake eyes, we have X kind of eggs? What if it layed eggs for drought conditions and then the monsoons set in. Or layed eggs for wet conditions and a drought set in? No intelligent design here, nope.
It has the necessary genes for either mode of life and depending on environmental conditions it turns on either one set or the other.
You're right, no intelligent design, just natural selection favoring the existence of alternate developmental routes determined by transcription factors.
Do you have a link? Or is it still missing? :-) None of the primates laid eggs, so far. None of the tree climbers had opposable thumbs, so far. There is absolutely nothing to validate this as more than someone's active imagination.
Philosophy is the argument for proof of faith and belief in things unknown. None have ever produced proof and all have been refuted also by argument. Of 400 religions which is proved or disproved by argument. Don't they all make the argument that each is the only truth.
Why in the world would they do that?
No, no intelligent design there. The eggs are the same, the difference comes in a developmental switch that is affected by environmental conditions. These developmental divergences are often subtle in their beginnings, but have a profound effect on the adult animal.
The real question would be: What happens if the switch is set to aquatic and there is a sudden drought or vice versa? A short term disaster for the critter.
CTM doesn't appear to be chasing that car, though.
These genes turn on IN water? How does it know there will be no water at the end of the gestations period? How does it know it's babies need to crawl out of the water and survive without water when the eggs are laid IN water? How does the animal know that it is a drought or wet season at the time of egg laying if the eggs are laid in water? Is it intelligent design or the animal is psychic and knows that at the end of the gestation period there will or won't be water, and its babies need to be aquatic or reptillian?
I know. We've had quite civil discussions.
You are asking the wrong people. It's the ID crowd that needs to explain how you anticipate need. Darwinian evolution doesn't anticipate need. Those individuals that are best adapted to current conditions leave more offspring. It's a bell curve thing, not an either/or.
If you want details, you'll need to provide me with some. I'm searching for a sub-Saharan amphibian that alternates between something like a newt and eft state, but not having any luck. Was this a frog? A toad? A salamander? You don't remember the name at all?
You were totally unaware of this?
Ever hear of "Frankenfood"?
Beats me. According to the evolutionist anything is possible. Not only did we lay eggs once, we laid them while swinging from trees. There's nothing to validate this as anything but someone's over-active imagination. I look at my little cocker spaniel and don't think of her as a 115th cousin once removed. Yes we have a few things in common as mammals, air breathing lungs for one, live birth for two, but other than that I can't see some critter crawling out of a cess pool and deciding to be a dog or a human. IF we were dependent upon water/drought conditions then yes, maybe I could see us becoming fish or amphibious. That would leave us two, possibly three, animal forms on earth that could survive under water/air/both conditions. But a fish crawling upon land and thinking "hmmm, do I want to be a cocker spaniel or a human....decisions decisions."
We have walked on the moon, explored Mars, measured light from distant galaxies, broken much of the human genetic code and still nobody can say how we went from fish to human or provide definitive proof thereof. I'm keeping an open mind, just saying there IS no proof that evolution, a/k/a Darwinism, is nothing more than junk science.
There are climatic types that are named after these zones.
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