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.
How long did the T. Rex roam the earth before extinction banged its gong?
BWAAAAAAAAAAAAAAAAAAAAAAAHAHAHAHAHAHA!!
"No it isn't. You are yet again forgetting about selection."
Incorrect. Selection isn't in question. It isn't forgotten; it simply isn't controversial.
Instead, you are unaware of the mathematical probabilities of "randomness."
Remaining unchanged over vast amounts of time is contradictory to vast amounts of random mutations.
Probably a few thousand or a few tens of thousands of years. Last summer, scientists had to break a trex leg bone in half to get it on a small helicopter, and this is what they found inside the thing:
MSNBC/Reuters version of the story.
Anybody who figures that stuff is 70 million years old is basically deluded.
What an absolute dolt!
You have a problem in that you have been arguing all day with unsupported claims you simply made up.
You have no idea what the reproductive rate of dinosaurs was, and you have no idea what the mutation rate of crocodiles is. You simply made this stuff up.
Not bad for someone who travels among those who accuse evolutionists of having just so stories.
The just so story that fits all available evidence is that evolution. like dog breeding can produce rapid changes in body conformation under some conditions. Among those conditions is a relative lack of competition and predation. Such as after a mass extinction.
Between extinction events, body types change slowly. Alligators and crocodiles survived the last extinction event, and their body plan has not changed a whole lot.
Crocks and alligators have changed, however. They are not the came as they were 150 million years ago, despite you babbling about mutation rates.
And after you say, "All of them", please give me a numerical guesstimate. Would it have been in the millions do you suppose?
It's rather sad that you cannot or will not be more specific. Freedom of religion allows you to believe in whatever you desire, regardless of your family's beliefs.
Why?
Lets make a clear point: "selection" isn't in question. Not "selection's" randomness or lack thereof; not "selection's" existence or lack thereof.
In short, any reference to "selection" is off topic at best, specious at worst, and more likely a simple-minded attempt at thread digression.
Is this single point clear? Probably not. You probably "feel" the need to argue about it in one way or another.
Nonetheless, ramblings about "selection" won't save your failed debate.
Now, if you want to talk about random mutations, that's a more worthy topic of debate.
Random (or not) "selection" is unworthy, however. It's non-controversial.
Carry on.
I believe the latest discoveries have pushed it back to about 70MYA (70MYA-65MYA = 5MY)....Immediately before then you have Daspletosaurus and Gorgosaurus, basically smaller relatives...
More name-calling from you, I see.
I doubt that you are capable of anything more intelligent, though.
Okay. Let's say the T. Rex roamed the earth for 5 million years. How many do you suppose would have ever existed in that amount of time? Thousands? Tens of thousands? Millions? Tens of millions?
According to the official ID mantra, MSNBC is a liberal rag not to be trusted. I read the linked article and I agree.
What?!? That is not even close to evolutionary theory. Selection pressure has a much greater influence on rate of change; mutation rate has very little impact. A species with very few mutations but in an environment that places serious survival pressures on that species will see a greater evolutionary rate of change than a species with a high rate of mutation but very little pressure from its environment to change. Sharks have evolved more "slowly" than other species of fish, not because we can say anything about the "rate of mutation" in sharks versus those fish (which wouldn't be constant in either, anyway... hence the term random), but because any mutation would be unlikely to make a shark better adapted to its environment (it already fits its role in its environment very well).
Your entire argument is based on a premise about what evolutionary theory postulates that is completely wrong. If you're going to argue against something, at least understand what you are arguing against first! Jeez...
What's harder than getting a pregnat T-rex aboard the Arc?
Extinction events are rare. For all practical intents and purposes you could just say that body types change slowly, period.
You could also say that changes in body types appear suddenly (e.g. in the fossil record), though rarely. Same thing.
Whether such evidence supports an evolutionary process or an external bias is another thing entirely, however.
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