Marc Bolan & T-Rex

[Jon_in_london]

It occurs to me that T rex is a rather odd creature. How and why did evolve those great big hind legs which it walks on while having a massive tail to counter-balance itself? And those funny little arms?

I just dont seem to be able to figure out how this would have come about by natural selection.

:confused:

[Andonyx]

Originally posted by Jon_in_london

I just dont seem to be able to figure out how this would have come about by natural selection.

:confused:

You should have seen what didn't get selected!

[c0rbin]

The Lord works in mysterious ways.

:p

[arcticpenguin]

Have you ever read anything about South American Terror Birds? Flightless birds up to 3 meters tall that were prominent in South America before the land bridge with North America popped up. http://www.bbc.co.uk/education/darwin/exfiles/terrorbird.htm

T-Rex was not an isolated species. It is the last in a long line including Allosaurs and others. That doesn't answer the 'why', but it does address the evolution angle.

If you have teeth like a T. Rex, you do not need arms for grappling prey. One bite kills. Bipoedalism? Perhaps for speed.

[c0rbin]

If Harryhausen movies are any indication, huge strong legs to hold something down while your huge strong toothy jaw ripps bits up and out would work.

[arcticpenguin]

Cassowary - http://www.ozramp.net.au/~senani/cassow.htm
http://home.mira.net/~areadman/casso.htm

The Cassowary is a large flightless bird. It can grow to almost two metres in height and can weigh up to 60kgs (130lbs).

The Cassowary has strong powerful legs with dagger-like claws on its toes. It defends itself by kicking. Its kick is powerful enough to rip open a person's stomach or even kill the person.

So the basic body plan, a bipedal predator with weak arms/wings and dangerous teeth/beak is certainly not unique.

[Jon_in_london]

Originally posted by arcticpenguin

If you have teeth like a T. Rex, you do not need arms for grappling prey. One bite kills. Bipoedalism? Perhaps for speed.

Well, thats the thing. Y'see, four legs are better than 2 when it comes to running. Its actually a disadvantge to be bipedal when it comes to sheer locomotive speed/power. SO although it may not be neccesary to have arms for grappling when you have teeth that size, ir still isnt an advantage to have silly little army-warmys sticking out of your chesty-westy (Plus it looks stupid on a ferocious predator doesnt it?).

I think its because T Rex wasnt a fast runner, maybe not even a predator after all but a scavenger who only had such big teeth for ripping chunks off rotting diplodocus and scaring away the competition?

[arcticpenguin]

Since we're venturing off into the land of complete BS, how about this scenario?

T. Rex evolved bipedalism for the extra height, to give it a better field of view. Once bipedal, large arms are no longer an advantage but a disadvantage.

OR

T. Rex's ancestors evolved teens-weensy arms for a completely different reason, and T. Rex just inherited that trait. That would give it a good parallel to the Terror Birds.

[chance]

I seem to recall that all Dinosaurs evolved from a common bipedal ancestor, basically a smaller version of a T Rex. The herbivores evolved from the carnivores and have dropped on to their forelimbs but still retain the imbalance of the larger rear legs (with some exceptions).

[FutileJester]

Originally posted by Jon_in_london
I think its because T Rex wasnt a fast runner, maybe not even a predator after all but a scavenger who only had such big teeth for ripping chunks off rotting diplodocus and scaring away the competition?

I know I've seen/read/heard this somewhere, about the evidence pointing to TRex being a scavenger. IIRC, one argument was that the teeth are better designed for crushing bones than many contemporaries whose teeth were more specialized for ripping flesh. Hunter gets the meat, scavenger gets the bones.

[Badger]

I recall reading (an old Discover magazine?) that based on bone density and muscle attachment, these "teensy" arms could still lift 400 lbs each.

I await correction.

[shemp]

The Dinosaur Sketch from "Monty Python's Flying Circus" and "Monty Python's
Previous Record"

Television Host (Graham Chapman): Good evening. Tonight - dinosaurs. I have here sitting in the studio next to me an elk. Aaagghhhh! Oh, I'm sorry, Anne Elk, Mrs Anne Elk.
Miss Elk (John Cleese, as a very prim lady): Miss.
Host: Miss Anne Elk, who is an expert on the...
Elk: No, no, no, Anne Elk.
Host: What?
Elk: Anne Elk, not Anne Expert.
Host: No, no, I was saying that you, Miss Elk, were an, A.N. not A.N.N.E.,
expert...
Elk: Oh!
Host: ...on elks - I'm sorry, on dinosaurs.
Elk: Yes, I certainly am, Chris, how very true, my word yes!
Host: Now, Miss Elk - Anne - you have a new theory about the brontosaurus.
Elk: Could I just say, Chris, for one moment that I have a new theory about
the brontosaurus?
Host: Er... exactly. What is it?
Elk: Where?
Host: No, no, no. What is your theory?
Elk: Oh, what is my theory?
Host: Yes.
Elk: Oh what is my theory, that it is. Yes, well you may well ask, what is my
theory.
Host: (slightly impatient) I am asking.
Elk: And well you may. Yes my word you may well ask what it is, this theory
of mine. Well, this theory that I have--that is to say, which is mine--
...is mine.
Host: (more impatient) I know it's yours. What is it?
Elk: Where? Oh, what is my theory?
Host: Yes!
Elk: Oh, my theory that I have follows the lines I am about to relate.
(Coughs) Ahem. Ahem. Ahem. Ahem. Ahem. Ahem.
Host: Oh God.
Elk: Ahem. Ahem. Ahem. Ahem. Ahem. Ahem. Ahem. Ahem. Ahem. Ahem.
Ahem. Ahem. [Impatient noises from Host] The Theory, by A. Elk. That's
A for Anne, it's not by a elk.
Host: Right....
Elk: This theory which belongs to me is as follows. Ahem. Ahem. This is how
it goes. Ahem. The next thing that I am about to say is my theory.
Ahem. Ready?
(Host moans)
Elk: The Theory by A. Elk brackets Miss brackets. My theory is along the
following lines.
Host: Oh God.
Elk: All brontosauruses are thin at one end, much MUCH thicker in the middle,
and then thin again at the far end. That is the theory that I have and
which is mine, and what it is too.
Host: That's it, is it?
Elk: Right, Chris.
Host: Well, Anne, this theory of yours seems to have hit the nail on the head.
Elk: And it's mine.
Host: (ironical) Thank you for coming along to the studio.
Elk: My pleasure, Chris.
Host: Er...Britain's newest wasp farm...
Elk: It's been a lot of fun.
Host: ...opened last week...
Elk: Saying what my theory is.
Host: Yes, thank you.
Elk: And whose it is.
Host: Yes. ...opened last week...
Elk: I have another theory.
Host: Not today, thank you.
Elk: My theory number two, which is the second theory that I have. Ahem!
This theory...
Host: Oh look...shut up!
Elk: ...is what I am about to say...
Host: Oh please shut up!
Elk: ...which, with what I have said, are the two theories that are mine and
belong to me.
Host: Look, if you don't shut up I shall shoot you.
Elk: Ahem! My brace of theories, which I possess the ownership of, which
belongs to me...

(BANG!)

(Pause)

Elk: Ahem. The Theory the Second by Anne...

(MACHINE GUN FIRE)

[spoonhandler]

Hi all.

Dinosaurs aren't in my field, but is it possible that little arms were still useful for personal grooming activities?

I have no idea what hygiene requirements a T. rex would have, but perhaps it was useful to have claws to scratch your nose or pick your teeth. Many modern creatures have regular activities designed to prevent illness and dysfunction - presumably dinosaurs did as well.

Maybe they needed arms and hands for mating or parenting activities. Their purpose did not need to be confined only to feeding or self-defence. Do we know if they constructed egg mounds, tore down trees, scraped in hillsides or whatever?

I know we have all these apparently incredibly accurate CG portrayals of a day in the life of a dinosaur but I find them way too speculative most of the time. Daily activities are often suggested for these beasts, but what do we really know about them?

:)

[Tez]

kangaroos

[spoonhandler]

That's scary - I'm Australian and I didn't even think of them.

They use their paws a lot - scratching, grasping, fending off each other, protecting infants, stealing food from the paper bag in your hand and so on, but if they didn't have them, they wouldn't be able to graze - they'd fall forward and land on their nose.

I'm not sure if T. rex proportions allow for the same possibilities...

[Luceiia]

Originally posted by Jon_in_london
It occurs to me that T rex is a rather odd creature. How and why did evolve those great big hind legs which it walks on while having a massive tail to counter-balance itself? And those funny little arms?

I just dont seem to be able to figure out how this would have come about by natural selection.

:confused:

Jon,

Try reading this page:
http://salmon.psy.plym.ac.uk/year3/psy364criticisms-evolutionary-psychology/psy364criticisms-evolutionary_psychology.htm

There's a LOT there, and much more that's linked or referred to. Especially near the middle of the page (search for "spandrels" if you don't care to read the first half of the page) and on to the bottom from there you will find (I think) quite a few different ways of looking at adaptation. Those forelegs may have been useful at some point in the past and are now wasting away (appendix?); maybe becoming something useful in the future; may have arisen from structural needs in that part of the body (panda's thumb); may be strictly decoration.

Or if you're in a wanton mood, head directly to the paper by Gould and Lewontin that makes some suppositions about those very legs to which you refer:
http://www.aaas.org/spp/dser/evolution/history/spandrel.shtml

Luceiia
My guess is they wanted dainty hands to stir their hot chocolate on cold mornings.

[Ove]

Good but what is the connection to Marc Bolan? (Other than he named his band after one).:confused:

[The Don]

T-Rex survived becuase the other dinosaurs made little roll-up cigarettes which they smoked to excess. As a result they all died of smoking related diseases such as heart attack, cancer and coughing rather loudly when there's a predator around.

As a result only the non-smoking dinosaurs survivied (hence crocodiles, have you ever tried smoking under water ?)

T-Rex's tiny arms are a result of this natiral selection process

[Crossbow]

Simply looking at animal and trying to understand how it came into its present form is a rather difficult exercise.

For what it is worth, here is what I do.

1) Find out how long the animal has been in it present form,

2) Find out what other animals preceded it,

3) Compare and contrast the animal's current environment with the environment that preceded it,

4) And when dealing with extinct animals, try to find contemporary animals with similar appearance/structure and learn what you can from them.

By putting together all of these pieces one can often get a better idea of why the animal looks like it does.

I hope this helps!

[Segnosaur]

I might be able to add some stuff to the debate....

Why smaller arms? It was mentioned that T. Rex balanced itself, using its tail as a counterweight. Every pound in front had to be counteracted by the tail. By making the arms smaller (especially if they weren't critical in hunting and killing prey), its head and jaws could be made bigger, without requiring extra counterweight in the tail.

Someone mentioned that T. Rex may have been a scavenger. Right now, that issue is still under debate. But, I did see a science program where they had found a skeleton of a dinosaur which had a piece of its spine bitten off, but survived (it showed evidence of healing). The only dinosaur that had the ability to bite though bone like that that we know of is T. Rex.

Note: I got my information from dinosaur documentaries on The Learning Channel and Discovery, so who knows if they are up to date in their research.

[xouper]

bump