Hello!
Posted on 07/03/2006 12:32:51 PM PDT by Al Simmons
In the 1993 movie Jurassic Park, one human character tells another that a Tyrannosaurus rex can't see them if they don't move, even though the beast is right in front of them. Now, a scientist reports that T. rex had some of the best vision in animal history. This sensory prowess strengthens arguments for T. rex's role as predator instead of scavenger.
Scientists had some evidence from measurements of T. rex skulls that the animal could see well. Recently, Kent A. Stevens of the University of Oregon in Eugene went further.
He used facial models of seven types of dinosaurs to reconstruct their binocular range, the area viewed simultaneously by both eyes. The wider an animal's binocular range, the better its depth perception and capacity to distinguish objectseven those that are motionless or camouflaged.
T. rex had a binocular range of 55, which is wider than that of modern hawks, Stevens reports in the summer Journal of Vertebrate Paleontology. Moreover, over the millennia, T. rex evolved features that improved its vision: Its snout grew lower and narrower, cheek grooves cleared its sight lines, and its eyeballs enlarged. ...
Stevens also considered visual acuity and limiting far pointthe greatest distance at which objects remain distinct. For these vision tests, he took the known optics of reptiles and birds, ranging from the poor-sighted crocodile to the exceptional eagle, and adjusted them to see how they would perform inside an eye as large as that of T. rex. "With the size of its eyeballs, it couldn't help but have excellent vision," Stevens says.
He found that T. rex might have had visual acuity as much as 13 times that of people. By comparison, an eagle's acuity is 3.6 times that of a person.
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T. rex might also have had a limiting far point of 6 kilometers, compared with the human far point of 1.6 km. These are best-case estimates, Stevens says, but even toward the cautious end of the scale, T. rex still displays better vision than what's needed for scavenging.
The vision argument takes the scavenger-versus-predator debate in a new direction. The debate had focused on whether T. rex's legs and teeth made it better suited for either lifestyle.
Stevens notes that visual ranges in hunting birds and snapping turtles typically are 20 wider than those in grain-eating birds and herbivorous turtles.
In modern animals, predators have better binocular vision than scavengers do, agrees Thomas R. Holtz Jr. of the University of Maryland at College Park. Binocular vision "almost certainly was a predatory adaptation," he says.
But a scavenging T. rex could have inherited its vision from predatory ancestors, says Jack Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont. "It isn't a characteristic that was likely to hinder the scavenging abilities of T. rex and therefore wasn't selected out of the population," Horner says.
Stevens says the unconvincing scene in Jurassic Park inspired him to examine T. rex's vision because, with its "very sophisticated visual apparatus," the dinosaur couldn't possibly miss people so close by. Sight aside, says Stevens, "if you're sweating in fear 1 inch from the nostrils of the T. rex, it would figure out you were there anyway."
Stevens, K.A. 2006. Binocular vision in theropod dinosaurs. Journal of Vertebrate Paleontology 26(June):321-330.
Hello!
Once again, you are incorrect.
Here's why:
You have a population of a specific animal.
In this population, under one scenario you have zero mutations but large amounts of Selection pressure.
Will you get speciation? No. At most, different pre-existing examples will survive, thrive, or go extinct...but no new genetic changes will be introduced into the DNA itself.
Under the second scenario, you have the same population but with no selection pressures (e.g. a lab or zoo) and massive mutations (e.g. from radiation, viri, etc.).
In this case, speciation *can* occur (e.g. Man-made pigs that produce human growth hormone).
So is "selection" more important to speciation than mutation? Absolutely not, per above.
So these mythical *hard-core evo-losers* pressured the scientists into changing their stories, because of... what?
Because of what? Because of whatever causes them to pressure judges, school boards, and every manner of elected official to have their own ideological doctrine taught as a "fact" in public schools at public expense and to forbid the mention of any and all competing theories in those same schools, I guess. Most people would say "because of ideology."
I suspect that the Bible may have defects along this line ....
Incorrect. The alligators alive today would be seen by a time-traveler (e.g. modern paleontologist) 20 million years ago.
Without mutations, you can't have speciation.
Who said anything about "without mutations"? (Straw Man Fallacy). I made a statement about comparative mutation rates, one that poked a hole in your original assertion. A low mutation rate can lead to a high rate of change, and a high mutation rate can lead to very little change, depending upon the environmental pressures on a species. Not only does this destroy your original statement, it destroys your whole point on this thread. The breeding frequency of the T. Rex has far less importance than the environmental pressure they were under, and likewise that for modern alligators. To assert otherwise is to be (willfully, it appears... which would be a sin. Or do you believe that falsehood in the service of "good" is not sin?) ignorant of the actual theory of evolution.
To sum up. You stated that mutation rates must be proportional to evolutionary rates of change for the theory to be viable. This is flat wrong. Mutation rates are only one (minor) variable in the picture. Low mutation (not no, just low, just in case you have trouble separating the two) populations can show a greater rate of change than higher mutation populations due to other more important variables.
Glad to see that you are one of those YEC'rs.
Naturally that's wrong, per probability math, but nice try.
You've now changed your argument to "low" changes/rates of mutation rather than "no" rates of mutation. This is because you've self-identified the importance of mutations compared to selection.
Which is to say, you recognized that you were wrong, even though you won't admit it.
Selection alone *can't* lead to speciation, but Mutation alone *can* lead to speciation.
That means that mutation is more important to speciation (not necessarily to survival) than "selection."
Again, you are seriously deluded.
That's meat, pure and simple.
That's incorrect, though you have managed to grasp that your own counter-argument hinges on my example being in error.
Too bad.
What my example does is point out the two most extreme situations:
#1 is selection pressures with no mutations, and
#2 is mutations with no selection pressures.
There is no "nonsense" about such extremes. They can easily exist in a lab or zoo, for example.
And they illustrate which is more important: selection or mutation.
Keep thinking about that point and eventually you'll catch on.
Notice how many of his arguments are based on the either-or logical fallacy? Either you have lots of mutations or none. Either you have completely random mutation causing speciation or the theory of evolution is false. So far most of his points have been set up to be binary, with no recognition of third options. It will be interesting to see if this is the only intellectual format he can generate...
Link?
see post #151
Post 151 in no way cites mutation rates. He's making it all up.
On the contrary, it's **NOT** a logical fallacy when it actually occurs (e.g. in the lab).
Selection pressures don't have to exist (e.g. in a zoo). There's no fallacy there.
Mutations can happen without selection pressures (e.g. in a lab that is creating pigs to produce human growth hormone).
Which is to say, my examples can't be logical fallacies. Fallacies don't happen. My examples do.
> The species alive today have remained virtually unchanged for scores of millions of years...
Wrong again. Repetition of a factually incorrect statement does not make the statement correct. Crocodilians have been evolving and changing drastically since before they were crocodilians.
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