Creationism/Evolution
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Title: The Wrists of Birds Reveal Evolution Undoing Itself
Source:
Smithsonian
URL Source: http://www.smithsonianmag.com/scien ... doing-itself-180953964/?no-ist
Published: Jan 22, 2015
Author: Elizabeth Quill
Post Date: 2015-01-22 07:47:08 by cranky
Keywords: None
Views: 2123
Comments: 7
Contrary to earlier claims, a new study shows that evolution may be reversible
Are you sitting down? Good, because you may be shocked to learn that evolution can retrace its steps. A recent study of the wrists of modern birds finds that a bone lost from dinosaurs for tens of millions of years reappeared when dinosaurs evolved into birds and took flight.
In the four-legged ancestors of dinosaurs, wrists were robust, weight-bearing joints with as many as 11 bones. When two-legged dinosaurs evolved some 230 million years ago, though, the wrists, no longer supporting such weight, became comparatively dainty. The forelimbs of the meat-eating raptors took on the task of manipulating prey, and the number of wrist bones shrank to just three. Among those that disappeared was a knobby bone called the pisiform.
Alexander Vargas of the University of Chile and his team decided to investigate the next steps in this evolutionary tale by studying not just fossils but also embryos of today’s birds, including chickens, pigeons and parakeets. Ancestral features are often visible in a developing embryo; human and chicken embryos, for example, have folds in the neck similar to those that become gills in fish.
When meat-eating dinosaurs evolved into birds, the wrist joint in the wing, between the middle and final segments, morphed again—increasing flexibility so the wing could fold back against the body. Birds also evolved a bone in the same place as the pisiform, to transmit force to the wing. Anatomists deemed it a new bone, the ulnare.
The 19th-century biologist Louis Dollo taught that evolution is irreversible; once a structure is lost, that pathway is closed forever. It’s a principle now known as Dollo’s law. But in analyzing the development of the ulnare, Vargas showed that it is, in fact, the re-emergence of the pisiform. “While the physical expression of a gene may be suppressed, it doesn’t mean the possibility of generating that structure has disappeared,” says Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles County. “The gene is still there, it’s just dormant.”
This isn’t the first time Dollo’s law has been challenged. Some mites have returned to their free-roaming ways after countless millennia living on animal hosts. And a tree frog from South America lost its lower teeth only to re-evolve them after 200 million years. Within the human embryo, there is similar potential. Perhaps the very bone you are sitting on, your coccyx, is ready to re-evolve a tail at some future moment when humans might need it again to hang from trees. (1 image)
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Perhaps the very bone you are sitting on, your coccyx, is ready to re-evolve a tail at some future moment when humans might need it again to hang from trees.
I've heard stories about human babies being born with tails. But I always thought that they were regarded as genetic "throwbacks" or deformities.... not "re-evolution."
Google reveals some pictures of people with tails... many of which are obviously digitally faked... but whether the others are legitimate or not... well I don't know... the whole idea is just too creepy for me to think about this early in the morning.
"Some people march to a different drummer — and some people polka."
#2. To: cranky (#0)
Contrary to earlier claims, a new study shows that evolution may be reversible
Darwin himself said as much from the very beginning.
It is only shallowly educated people who think that life forms are supposed to only evolve to higher and higher forms of life. They can devolve as well. Or features of a species may disappear and reappear much later. Or all of the above in various combinations.
#3. To: cranky (#0)
I chuckle every time I see these pointless arguments over this pseudo-science.
Obama has played at being a president while enjoying the perks … golf, insanely expensive vacations at tax-payer expense. He has ignored the responsibilities of the job; no plans, no budgets, no alternatives … just finger pointing; making him a complete failure as a president
#4. To: cranky (#0)
Genotype is more like a library. Genes can be turned off and on.
#5. To: TooConservative (#2)
Darwin himself said as much from the very beginning
Darwin theory does not include genetics
#6. To: cranky (#0)
Contrary to earlier claims, a new study shows that evolution may be reversible
This is no secret to anyone who has checked DNC backed candidates over the last 30 years or so.
There are chipmunks brighter than Goober Gore and Joe Biden.
Why is democracy held in such high esteem when it’s the enemy of the minority and makes all rights relative to the dictates of the majority? (Ron Paul,2012)
#7. To: TooConservative (#2)
It is only shallowly educated people who think that life forms are supposed to only evolve to higher and higher forms of life. They can devolve as well.
In other words,"use it or lose it".
Why is democracy held in such high esteem when it’s the enemy of the minority and makes all rights relative to the dictates of the majority? (Ron Paul,2012)
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