Why We Walk on Two Legs: It's Easier

[ASCLEPIADES]

Salve, guys and Ladies!

I think the real question would be where did humanity begin; what could the first human do and his predecessors couldn't that made him so utterly different?

[M. Porcius Cato]

Salve, guys and Ladies!

I think the real question would be where did humanity begin; what could the first human do and his predecessors couldn't that made him so utterly different?

Unanswerable.

[Kosmo]

Could a cantitative increase of inteligence led to a calitative jump?

I think this is case for humans. They became smarter and smarter and after a certain point intelligence becames different not only greater.

[caldrail]

Two legged locomotion isn't so suprising. Reptiles discovered that long before dinosaurs - there's a recent discovery of a reptile (that incidentially resembles later dinosaurs - spooky!) that was featured in National Geographic. Dinosaurs themselves made good use of two legs especially where speed was essential, either in attack or retreat, and their descendants the birds use two legs as standard.

Do you know if there's anything about that on the net Caldrail?

 

No, I've no idea. If I still have the issue hanging around somewhere I'll definitely dig out the info. The upshot is that bipedalism is primarily useful for speed. Whilst its true that animals like the cheetah are well adapted to four legged acceleration, minimal contact with the ground and length of gait is part of the answer. The spine of the cheetah is particularly flexible for this reason, allowing the animal to increase its stride by using the length of its body effectively.

[Marcus Caelius]

OK, you've gone from "there are zero qualitative differences" to ...

 

Well of course I've shifted my ground, and shame on me for letting you force me into it. It's a big subject, and my post was only the bottom line. It's purpose was never to show present similarity as more than evidence of common ancestry, and I allowed you to divert the conversation into the areas of technical differences in the present; I shifted my ground because I allowed you to shift the argument. Of course there are differences in our thinking! We are now two different species! But there are enough practical similarities, coupled with the fossil record, to belie the claim that we are fundamentally different from the apes.

 

I'm out of this conversation, now. It's raising my blood pressure too high.

[Marcus Caelius]

The upshot is that bipedalism is primarily useful for speed. Whilst its true that animals like the cheetah are well adapted to four legged acceleration, minimal contact with the ground and length of gait is part of the answer. The spine of the cheetah is particularly flexible for this reason, allowing the animal to increase its stride by using the length of its body effectively.

 

Segue: Perhaps(?) related is something I've kind of always half-wondered about, is the direction that ours and other primates' knees bend. What role did that play in human evolution? Is it somehow advantageous for natural selection? If so, how? With our knees bending forward, it is virtually impossible to travel on all fours; primates are among the slowest animals on the planet; prehensile toes seem to be more of an advantage in the trees, and so on. Is the shape of our legs just a purposeless mutation that isn't detrimental enough to have us "selected out"? What role does it play in bipedalsim?

[ASCLEPIADES]

Two legged locomotion isn't so suprising. Reptiles discovered that long before dinosaurs - there's a recent discovery of a reptile (that incidentially resembles later dinosaurs - spooky!) that was featured in National Geographic. Dinosaurs themselves made good use of two legs especially where speed was essential, either in attack or retreat, and their descendants the birds use two legs as standard.

Do you know if there's anything about that on the net Caldrail?

 

No, I've no idea. If I still have the issue hanging around somewhere I'll definitely dig out the info. The upshot is that bipedalism is primarily useful for speed. .

 

Salve, guys!

In this typical LIST, the ostrich is the only one bipedal among the 20 speedest land animals.

National Geographic has a lot in bipedalism studies; I posted a link before in this thread.

Here is a very good link in COMPARATIVE BIPEDALISM; one of its main conclusions is:

 

"Another unifying trait in bipedalism is the two general ways in which it has developed. In the case of thecodonts, lizards, and the non-primate mammals, bipedalism evolved for its advantages to speed in either escaping prey or pursuing predators. In the case of primates and birds, bipedalism evolved because the forelimbs were highly specialized for other purposes".

Edited July 23, 2007 by ASCLEPIADES

[M. Porcius Cato]

there are enough practical similarities, coupled with the fossil record, to belie the claim that we are fundamentally different from the apes.

 

I agree. Fundamentally, we're all animals that survive and reproduce by maximizing the output of whatever advantages that we have.