New Study Shows Tyrannosaurus Rex Evolved Advanced Bird-Like Binocular Vision

Science News Online ^ | June 26 2006 | Eric Jbaffe

[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.

[Southack]

"The problem is with your model of what is happening. The hand is not reshuffled for each generation."

The problem is not with my model, the issue instead resides in the question of randomness or external bias.

If mutations are random, then there may be no mutations in a given child, or 1 mutation, or thousands. A deck might not be shuffled at all...it might have a single card moved...or it might be shuffled entirely.

However, it would be an **arbitrary** restriction to claim that only 1 mutation happens at a time.

Arbitrary restrictions are strong indicators of external bias, not randomness, by the way.

[js1138]

If mutations are random, then there may be no mutations in a given child, or 1 mutation, or thousands. A deck might not be shuffled at all...it might have a single card moved...or it might be shuffled entirely.

Point mutations would be considered copy errors. Errors are edited, so any that get through would tend to be small. Large errors would likely be fatal, so they would immediately be lost.

So there is a bias towards small errors. This has nothing to do with intelligence in the sense of anticipating what is needed or what would be useful.

[Southack]

"Errors are edited, so any that get through would tend to be small. ... So there is a bias towards small errors."

I agree fully.

[b_sharp]

The fact that we as intelligent designers can produce novel phenomena or reproduce natural processes in the lab does not limit those tasks exclusively to designers. It says more about our ability to mimic than it does about nature's need for an intelligent agent.

Why do you IDists use such a transparently manipulative and weak argument?

[b_sharp]

Your calculation, 3¹⁹⁵³, produces a number of full genome changes, and a number of 1952 point changes, and a number of 1951 point changes, and so on...

Those larger mutations aren't likely to happen.

[Southack]

"Those larger mutations aren't likely to happen."

I agree with you on that point, fully. Please see Post #663.

[Southack]

"The fact that we as intelligent designers can produce novel phenomena or reproduce natural processes in the lab does not limit those tasks exclusively to designers."

That's very true, however, we can calculate the mathematical probabilities for such phenomena occuring randomly...without external bias (e.g. Man).

[b_sharp]

"That's incorrect, mathematically (this point is not arguable). Math doesn't care if you make your changes one at a time or billions at a time; the probabilities for achieving a desired sequence are the same."

No one is arguing that all the possible permutations of a string with a given alphabet is not represented by aⁿ where a = the number of possible choices at a position and n is the length of the string.

However, as I explained earlier, if you are restricting the changes to only one character change at a time from the original source it is not calculated with a permutation nor a combination.

You will note that your statement above is referring to a specific target outcome rather than any outcome that can do the job. If you are looking for a single outcome from a single trial the probability will indeed be aⁿ. However that is not how evolution works.

Evolution will always *effectively* terminate the search when the first successful outcome is found *in that iteration* (read generation). Once that one of many possible successful outcomes is found the iteration stops. The next iteration will start with the new string as the origin with the probability of that state being 1.

There is more than a single specific outcome that can be considered successful so the probability is not 1/aⁿ but x>1/aⁿ. To calculate this probability we would need to know 'x' which is currently undetermined but definitely greater than 1.

Evolution also uses numerous concurrent trials which mean each member of the population has a probability of x>1/aⁿ. This means the probabilities of all members of the population during the current iteration is added together. Only if you are demanding a specific member of the population experience a specific mutation do you multiply them together.

This is where non-intelligently directed selection affects the probability calculation. All those organisms with a deleterious mutation will be removed from the population leaving the majority of the population with a neutral but potentially non-neutral mutation. The rest will have beneficial mutations. A single generation represents a single iteration so each generation will produce a separate iteration. If the fitness level you as an intelligent probability calculator have deemed as the target outcome has not been reached then the second iteration is added to the first. This will repeat until the fitness level is reached.

However Evolution cares not a whit what you or I claim for a satisfactory fitness target, it will mindlessly produce it's own.

At no time in all of this is the probability of a successful outcome 1/aⁿ as you postulate.

[Southack]

"There is more than a single specific outcome that can be considered successful so the probability is not 1/an but x>1/an."

This is true and specifically dealt with in the math link that I posted earlier in this thread...which shows that X > 1 but so much less by so many orders of magnitude from a^N as to make very little difference to the probability math for non-biased results.

The bacteria experiment post by js1138, for example, could only produce 20 million unique DNA sequences out of 3^1953 potential combinations.

[b_sharp]

"That's very true, however, we can calculate the mathematical probabilities for such phenomena occuring randomly...without external bias (e.g. Man)."

Why the insistence on pure randomness?

Mutations are not randomly distributed throughout the genome, the chemistry of the DNA string makes some areas more prone to mutations than others. Some areas of the genome are more prone to ALUs. Some areas are corrected more faithfully than others.

Selection isn't random either. Once the mutations have increased the range of allele variation, the numerous modes of selection, working singly or in tandem, determine the direction the population will take.

You can't define 'random' to mean 'everything not directed by an intelligence'. There are many natural phenomena that produce nonrandom results.

[b_sharp]

You wouldn't by chance remember the number of JS's post would you?

[Southack]

582

[Southack]

"Why the insistence on pure randomness?"

Randomness or external bias is the essence of the debate between Evolution versus Intelligent Design.

Randomness can occur without any form of intelligent intervention, after all.

So do we have a DNA-processing-engine and a DNA data-structure with designed redundacy and some level of error detection/correction...or do we have purely random chemical interactions?

[b_sharp]

Thanks

[b_sharp]

"Randomness or external bias is the essence of the debate between Evolution versus Intelligent Design."

Not at all.

There is a tacit assumption in this statement that requires that 'order' be an exclusive result of intelligence. The assumption is wrong.

"Randomness can occur without any form of intelligent intervention, after all."

You keep making the same category error.

Randomness can occur without an intelligent agent, but so can non-randomness.

[Southack]

"Randomness can occur without an intelligent agent, but so can non-randomness."

I agree. No controversy there.

We can calculate or otherwise discern when non-randomness (e.g. bias) occurs without an intelligent agent, however. In those cases elements/entities are interacting based upon rules, laws, principles, etc.

For instance, water generally flows downhill. That's non-random. That's due to an external bias (e.g. Gravity). That's not due to a micro-managed intelligent intervention. This also means that we can predict that water will follow the lowest path, i.e. that a rule is being aderred to by the water flow.

If we can find this same sort of rule/law being followed/adherred to by DNA codons, then we would have evidence of non-intelligent bias.

That would be significant.

But for starters, the Evolutionary crowd needs to accept that there is an external bias in genetic systems (and I'm not talking about "Selection" but rather about the DNA genetic-code processing engine, error detection/correction, and DNA redundant data structure in the double-helix design).

Once past that point, the debate will then move to an intelligent or non-intelligent source for the bias in DNA iterations over time; the essence (restated) of the Evolution/Intelligent Design debate.

[Elsie]

;^)

[Elsie]

Neatly dressed in blue Capri pants and a sleeveless top, long hair flowing over her bare shoulders...

Would THIS have worked as well in the ORIGINAL article??

Sloppily clothed in stained lab pants, and a torn, blood splotched lab coat, with stringy hair stuffed into a too large cap; Mary Schweitzer sits at a microscope that is in a lab over flowing with many projects, her drawn face merely inches away from the computer screen (for her coke bottle glasses had been accidently smashed moments before); the network of thin, branching vessels barely identifiable.

[Elsie]

Evolution is about the accumulation of small changes; not winning Lotto.

Some say - "Prove that they accumulate." - don't just make a statement saying that they do.

[Elsie]

ARRGH!!!

You got 666!!!