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.
Do you have an argument of substance to offer?
When they do we may find out how it happens.
Until then, no one has seen it ~ they've guessed at it, and speculated about how it can happen, and so forth ~ I think it's going to be something far more complex than so far imagined, and will involve a bit more than the simple transfer of chemical information at the cellular level.
So, what is it stokes the fires of speciation?
No doubt it's not that transposition by itself ~
My point exactly. If we evolved from fish-laying eggs, to egg-laying mammals, why couldn't we be mammals that laid eggs while swinging from trees. Birds lay eggs in trees. Seems a natural progression that primates, along their evolutionary path, would lay eggs in trees, unless they'd already learned about the live-birth thing. Eggs are much less fussy (unless you're a penguin) requiring more attendance after hatching. On the other hand, live births incapacitate the female to a certain extent due to carrying and nursing her young. Not to mention the immediate demands of the newborn, whether hatched or birthed. Laying eggs and letting the young develop outside the mother is much less demanding than the newborn developing inside the mother. Nobody has explained how we went from one to the other. If so, and we are so smart, why did we adapt to the more cumbersome and demanding live birth instead of egg laying. Because we were too busy swinging from trees and that whole egg-sitting thing was just a bother in ADHD primates? We were too busy eating parasites off our neighbor to sit on our own eggs, so lets just evolve to pop out our young. We'll carry them on our back today, and as soon as the first Walmart opens in a few cajillion years we'll get one of those sling thingys to carry them. Evolution at its finest.
Early placental mammals were driven from Australia by marsupials due to their reproductive superiority.
The dispute is won with a single finding.
Then what directed it? Intelligence?
Evolutionary theory starts with the first imperfectly self-replicating organism. It matters not how this organism came to be.
Basic to the theory is the lack of an intelligence behind the life we see here, now. Hence the Great Debate among evolutionists, creationists and intelligent designers. Where the proto-organism came from would be central to the issue, don't you think?
Because by the time apes evolved their ancestors were far removed from the egg-laying mammals and were placental mammals.
Basic to the theory is the lack of an intelligence behind the life we see here, now. Hence the Great Debate among evolutionists, creationists and intelligent designers. Where the proto-organism came from would be central to the issue, don't you think?
"collage"?
It's a question that biologists are interested in, but it has zero relevance to how evolution works.
The question of whether evolution is random or not is simply not stated usefully. Variation is mostly random. It does not anticipate need. Selection is not random for a species. the conditions of the environment can be studied to any arbitrary degree of precision, and the environment determines which variants are most successful at producing offspring.
Evolution cannot produce a new feature simply because it is needed. If it could, species would not go extinct.
The variations that do get produced, by whatever mechanism, are all that selection has to work with.
See my earlier post to you, #52, above.
Your comment that evolution is "just a theory" is deliberately misleading. What else would it be? Why do you think that your attempt to belittle evolution as "a theory" means anything other than you do not understand the role of theory in science.
Rather than scoring a telling point against evolution, you may just have exposed your opinions of, and education in, science.
"The dispute is won with a single finding."
Of what?
I am seriously beginning to think the YEC idea of a "transitional" is having an animal morph (in a matter of seconds) into a totally different critter.
Based on the total lack of science literacy exhibited by the creationist posters, they must have gotten their biology education from old Michael Jackson videos.
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