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.
They are all of that.
"I do part with ToE on the evolution of man. But, I have no scientific evidence to back it up, so I won't argue it on this forum."
This is a serious question and I'm not looking to score points, just understand. Do you feel this way because it interferes with the "special" relationship between man and God?
Please restrict your comments to the 2nd grade level so they can be better understood by yellowdoghunter. i cannot believed that she went to collage.
Please restrict your comments to the 2nd grade level so they can be better understood by yellowdoghunter. i cannot believed that she went to collage.
I noticed that the scientific method is nearly identical to the philosophical branch of epistemology.
Someone's idea is a opinion void of facts and not supported by any evidence. A theory is defined as observed fact, evidence and explanation of the fact. Not someone's idea.
So a transition from fish to amphibians (that is, at the taxonomic level of "class") is not a transitional form? Move the goalposts much?
Is it also no big deal if an amphibian becomes a reptile? If a reptile becomes a primitive, egg-laying mammal? If a primitive mammal becomes a placental mammal? If a placental tree-dweller becomes a lemur-like primate? If a primate becomes a monkey? If a monkey becomes an ape? If an ape becomes a man? None of those are any harder than gill-breathing fish to lung-breathing, land-living, tetrapod.
Old science was indeed "Natural Philosophy". Indeed a Ph.D. is a Doctor of Philosophy, although there is precious little overt philosophy taught as part of science education today.
Philosophy is still a structural basis for science, but it is quite different from modern ideas of Philosophy.
Even in philosophy one must have logical reasoning to back up one's beliefs. Otherwise it becomes irrational epistemology. One does have the freedom to choose this as their preferred philosophy though.
My apology for not indicating sarcasm.
On that we agree. It explains a material fact. It is of a higher order of either faith, belief, opinion, or fact. Thats why theories are accepted over faith, belief, opinion, and fact. Maybe you should look up the definition of theory as it applies to evolution.
We make glass stronger than steel, however all things may be breakable. You might try throwing stones at a 5' diameter globe of bullet proof glass and see how you make out.
Isn't that functional relationship true by definition?
LOL! That's ok, I'll copy and paste my reply for use later--I'm sure I'll need it. ;-)
Actually, I've never heard it said that women suffer those side effects! :-D
Do you have an argument that addresses the substance of the claims, or -- like AmericansUnited -- is the entirety of your position built upon baseless ridicule?
Actually I never move the goalposts. I don't have to since nobody has gotten near the end zone yet. Fish to amphibians to reptiles to egg laying mammals is still not a link from fish to man. There are still aquatic animals in this century that adapt to drought conditions by becoming more amphibious and I've yet to meet a human that lays eggs, much less hang from trees on its days off, unless you want to discuss the welfare class.
There is nothing in the whole Darwin *theory* to support the fish-to-man theory, no matter how many times they "move the goalposts."
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.