Intelligence brought on by upright walking?

[John J. Bannan]

I had an idea that was new, at least, to me. Could walking upright have lead to man's intelligence? Walking upright changes the load bearing structure of our bodies. Instead of a horizontal spine, we have a verticle spine. The head just so happens to be at the end of that spine. A verticle spine can hold a lot more skull comfortably than a horizontal spine. When man first walked upright - suddenly his skull could grow much larger because there was more structural support for our brains. This lead to our increased intelligence. What do you think?

 

[mathman]

Man (defined by upright walking) split from apes about 7 mil yrs. ago. Man's brains became significantly larger around 2 mil. yrs. ago. That's a long interval.

 

[John J. Bannan]

True. But could those brains have grown significantly larger, if not for the extra support capacity of the verticle spinal column? In other words, would man's brains have grown larger even if he was still walking on all fours? Aren't our skulls just too big for comfortable knuckle walking?

 

[one_raven]

True. But could those brains have grown significantly larger, if not for the extra support capacity of the verticle spinal column? In other words, would man's brains have grown larger even if he was still walking on all fours? Aren't our skulls just too big for comfortable knuckle walking?

Wouldn't we have just developed stronger neck and back muscles?:bugeye:

 

[river-wind]

given the size and weught of dinosaur, hippo, elephant, etc,etc skulls, I'd say no.

The weight of the brain certainly would have had an effect on how the head needed to be stablized, but there are far too many examples of animals with heavier heads than ours walking on all fours without difficulty to think that the brain could not have grown before we became upright walkers.

 

[John J. Bannan]

Yes, but do any of those animals have brains as disproportionately sized to their bodies as our skulls are? Surely there are animals that walk on all fours that have bigger skulls than us. But, their bodies are also larger, thus reducing the proportional size of the brain to the body.
Stronger neck and back muscles requires a larger body size, which again reduces the proportional size of the brain to the body.

 

[river-wind]

So intelligence would be a factor of body size over brain size?

edit:
http://library.thinkquest.org/C0110299/brain/intelligence.php?page=intelligence1

go tree-shrew!

 

[iceaura]

Baby humans have huge heads compared with their bodies, and weak necks, but find quadruped locomotion quite easy - easier than balancing that big head way up in the air on two legs, for sure.

Kangaroos seem to have missed out on the advantages of vertical head support.

Maybe the structural task of supporting a horizontal head on a short neck is not that challenging compared with the task of controlling the inertia of a very heavy head on the top of a tall vertical pole, while running and jumping all over the place.

 

[John J. Bannan]

Kangaroos don't walk up right. Baby humans are not fully developed. Besides, crawling is not quadruped motion. And I've never seen a baby hunt down an antelope on all fours. Also, don't you have the same inertia problems with a head attached to a horizontal spine?

 

[John J. Bannan]

The tree shrew hasn't won yet. There is still controversy about it.

 

[Read-Only]

I had an idea that was new, at least, to me. Could walking upright have lead to man's intelligence? Walking upright changes the load bearing structure of our bodies. Instead of a horizontal spine, we have a verticle spine. The head just so happens to be at the end of that spine. A verticle spine can hold a lot more skull comfortably than a horizontal spine. When man first walked upright - suddenly his skull could grow much larger because there was more structural support for our brains. This lead to our increased intelligence. What do you think?

Interesting thought. But there's nothing to really support it. In fact, it could be argued equally convincingly that it's quite the other way around - that due to our increased intelligence, we started walking upright in order to take advantage of the greater sight-distance and increased speed of running.

 

[river-wind]

The tree shrew hasn't won yet. There is still controversy about it.

I think you mis-read what the "controversy" is about. the tree-shrew *has* the greatest brain/body ratio (and thus 'wins'); what it does not appear to have is the greatest intelligence, which means that brain/body ratio as a guage of intelligence is controversial, because it only kinda works.

 

[John J. Bannan]

The fossil record seems to indicate that upright walking in man's ancestors occurred prior to large brain development. Consequently, larger brain development did not cause upright walking. As for the tree shrew, his small presence does not unhinge what appears to be some correlation between brain/body ratio as a guage of intelligence. The tree shrew remains a rather tiny victory.

 

[iceaura]

Kangaroos don't walk up right.

Not quite. But they have most of the "advantages" of upright and/or bipedal head support available to them - and small heads.

Baby humans are not fully developed.

So? All the more reason for them to prefer the easier way.

Besides, crawling is not quadruped motion.

Is too. Four point stance, four point locomotion. Call it "knee walking", to go with the "knuckle walking" gorilla and "toe walking" horse and so forth.

Also, don't you have the same inertia problems with a head attached to a horizontal spine?

No. Check the distance from the leverage point to the weight needing control in, say, a 150 pound black bear or dog (center of head to front paw on ground in normal stride) and a 150 pound human (center of head to bottom of foot in normal stride).