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Origin Of Bipedalism Closely Tied To Environmental Changes
Space Daily ^ | 05-01-2002 | staff writer at Space Daily

Posted on 05/29/2002 2:11:46 PM PDT by Salman

Origin Of Bipedalism Closely Tied To Environmental Changes

Champaign - May 01, 2002

During the past 100 years, scientists have tossed around a great many hypotheses about the evolutionary route to bipedalism, to what inspired our prehuman ancestors to stand up straight and amble off on two feet.

Now, after an extensive study of evolutionary, anatomical and fossil evidence, a team of paleoanthropologists has narrowed down the number of tenable hypotheses to explain bipedalism and our prehuman ancestors' method of navigating their world before they began walking upright.

The hypothesis they found the most support for regarding the origin of bipedalism is the one that says our ancestors began walking upright largely in response to environmental changes – in particular, to the growing incidence of open spaces and the way that changed the distribution of food.

In response to periods of cooling and drying, which thinned out dense forests and produced "mosaics" of forests, woodlands and grasslands, it seems likely that "some apes maintained a

forest-oriented adaptation, while others may have begun to exploit forest margins and grassy woodlands," said paleoanthropologist Brian Richmond, lead author in the new study. The process of increasing commitment to bipediality probably involved "an extended and complex opening of habitats, rather than a single, abrupt transition from dense forest to open savanna," he said.

Richmond, from the University of Illinois, with anthropologist David Begun from the University of Toronto and David Strait from the department of anatomy at the New York College of Osteopathic Medicine, describe their findings, which involved a comprehensive review and analyses of the five leading hypotheses on the origin of bipedalism, in a recent issue of the Yearbook of Physical Anthropology. Other hypotheses that remain viable, according to the team: "freeing" the hands for carrying or for some kind of tool use, and an increased emphasis on foraging from branches of small fruit trees, which is the context in which modern chimpanzees spend the most time on two legs.

For their study, the researchers combined data from biomechanics – movement and posture, pressure distributions and strain gauge – and from finger-shape growth and development. They found that our prehuman ancestors had terrestrial features in the hands and feet, climbing features throughout the skeleton, and knuckle-walking features in the wrist and hand; that finger curvature is responsive to changes in arboreal activity during growth. Evidence from the wrist joint, in particular, "suggests that the earliest humans evolved bipedalism from an ancestor adapted for knuckle-walking on the ground and climbing in trees."

The YPA article, according to Richmond, is "the first attempt in decades to bring together all of the available evidence for the argument that the earliest human biped evolved from ancestors that both knuckle-walked and climbed trees, rather than from ancestors living exclusively in trees and 'coming down from the trees,' or walking on the ground in ways similar to modern baboons."


TOPICS: Culture/Society; Extended News; Philosophy
KEYWORDS: godsgravesglyphs; humanevolution; origins; thelatesttheory
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To: mamelukesabre
Also we sweat. We can persue other animals until they drop from heat exhaustion.

BTW An upright posture also reduces solar overheating by a large fraction.
81 posted on 11/05/2003 11:00:24 AM PST by null and void
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To: paulklenk
The original point bears repeating.

BTW, did you know your dog makes his own Vitamin C, and yet you cannot?
Why would God create humans to be inferior to dogs?
The answer has to do with "use it or lose it" and
is a powerful indicator that early hominids ate fruit so
exclusively that the need to make C was selected out and didn't come back.
Else, God is a lousy craftsman.
82 posted on 11/05/2003 11:10:27 AM PST by gcruse (http://gcruse.typepad.com/)
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To: Maceman
Pretty informative, except for that part about the blood going to the oranges.
83 posted on 11/05/2003 11:10:31 AM PST by Old Professer
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To: Sabertooth
Only city folk can't swim.
84 posted on 11/05/2003 11:12:46 AM PST by Old Professer
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To: VadeRetro
Did you ever try to drag a Wildebeast back to camp with a Lion hanging on to the other end? :>)
85 posted on 11/05/2003 11:17:51 AM PST by Old Professer
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To: U S Army EOD
We learned nothing from rabbits. We learned how to throw rocks at rabbits and how to cook rabbits. Technique.
86 posted on 11/05/2003 11:18:10 AM PST by RightWhale (Repeal the Law of the Excluded Middle)
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To: Physicist
Long distance travel as a goal implies higher-order reasoning; the greater the distance the more imaginary the goal. To this day, people will tend to walk in a great circle when lost absent a path or clear marker; I wonder where ancient Man thought he was going?
87 posted on 11/05/2003 11:29:18 AM PST by Old Professer
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To: RightWhale
Well for real, I am fixing to go into the commercial rabbit business. Will this possibly have any frenge benefits for me?
88 posted on 11/05/2003 11:44:01 AM PST by U S Army EOD (Just plain Wootten)
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To: RightWhale
Where would we be now, in your opinon, if PETA had evolved before the hunters?
89 posted on 11/05/2003 11:47:37 AM PST by U S Army EOD (Just plain Wootten)
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To: Old Professer
Man, is this an old thread come back to life.

I've never seen a wildebeast I wanted enough to argue up close with a lion. But you gnu that!

90 posted on 11/05/2003 11:53:12 AM PST by VadeRetro
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To: U S Army EOD
In those days people also hunted people.
91 posted on 11/05/2003 11:54:07 AM PST by RightWhale (Close your tag lines)
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To: RightWhale
Still do, but don't eat them so often. Probably worried about disease.
92 posted on 11/05/2003 11:57:42 AM PST by RightWhale (Close your tag lines)
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To: RightWhale
I think we still do that, but we just don't eat our kill as often.
93 posted on 11/05/2003 11:58:46 AM PST by U S Army EOD (Just plain Wootten)
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To: RightWhale
You beat me to it.
94 posted on 11/05/2003 12:00:22 PM PST by U S Army EOD (Just plain Wootten)
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To: Old Professer
Usually where he was headed unless he knew he was lost, if he didn't know he was lost he usually thought he knew where he was going if he thought that was where he was headed. When he got there it might not be the there he thought it was. Which would explain early maps. Which would also have to be carried upright because they would get dirty so they couldn't be read if you were kind of dragging them on the ground. These people would have become extinc.
95 posted on 11/05/2003 12:05:10 PM PST by U S Army EOD (Just plain Wootten)
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To: U S Army EOD
As a result of that movie, I at times wonder what certain young ladies would look like bent over at the waterhole.

With that thought is mind, I'll turn up my pacemaker to high. (G)

The 'natives' called our method the 'missionary position', obviously they preferred another.

96 posted on 11/05/2003 3:13:32 PM PST by Vinnie
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To: Sabertooth
But we also don't have a single fossil of an aquatic ape.

How would you recognize it? Aren't a lot of infra-human fossils found near ancient lakeshores?

The tow theories I find most intriguing are aquatic ape and William Calvin's
throwing theory of language and intellignece.

Granted, both of these are speculative, but I think they're basically good science, in that they tie together a lot of observations with one plausible theory.

The aquatic ape ties together physiology (body hair, fat) and behavior (swimming, anti-drowning reflex), and to some extent bipedalism (part of the weight being supported by bouyancy).

The throwing theory starts from the fact that people are the only anlimal that can throw accurately and the fact that this reqires timing more accurate than a neuron can provide, but which can be provided by many ganged-together neurons, and the hypothesis that throwing sticks and stones was an early method of hunting. He reasons that the large number of neurons needed for throwing was co-opted into providing the accurate timing needed for speech, and the sequencing needed for many other tasks that only people can do.

97 posted on 11/06/2003 5:48:42 PM PST by Virginia-American
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A Blast from the Past -- 2002.

To all -- please ping me to other topics which are appropriate for the GGG list. Thanks.
Please FREEPMAIL me if you want on or off the
"Gods, Graves, Glyphs" PING list or GGG weekly digest
-- Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
Gods, Graves, Glyphs (alpha order)

98 posted on 12/08/2006 10:42:44 AM PST by SunkenCiv (I last updated my profile on Thursday, November 16, 2006 https://secure.freerepublic.com/donate/)
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To: Maceman

What an interesting article and theory.

Thanks for the post.

And the theory fits our physiology like a glove.


99 posted on 12/08/2006 11:00:10 AM PST by StructuredChaos (Disorder is but misunderstood order; Order is naught but chaos structured.)
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To: Sabertooth

You write, "What aquatic mammals have hair primarily on their heads, armpits, and pubic regions?"

I respond:

What aquatic mammals stand on two and reside both on land and water? The uniqueness of this animal perhaps provides answers to your questions involving placement of hair.

For instance:

Ever go skinny dipping in the ocean? Ever get out of the water standing face forward to a cool breeze? I'd say my children owe much to the hair on my hrmpph. When you get into cold water at what point to you hesitate the most :)?

You write, "Are their non-aquatic non-primates with salty tears?"

I respond: Good question. The question invites the following inquiry: What evolutionary benefits flow from non salty and salty tears?

You write, "But we also don't have a single fossil of an aquatic ape."

I speculate: Perhaps our time adapting as an aquatic ape was limited geographically and temporally. And perhaps while adapted to water we were not adapted such that we could cross oceans or great distances by water. Accordingly, the adaptations could only be transmitted to other populations by land. Once fairly adapted to the aquatic condition the benefits associated with that adaptation were not just marginally advantageous to survival in aquatic environments but also greatly advantageous to populations living primarily on land. At some point the adaptations made us champions of the land - upright tool users ........ The old primates, indeed all land-dwelling animals, were no match for aquatic man. In point of fact, we are the aquatic ape. Our remains as fossilized are the remains of the aquatic ape. End of speculation.

You write, "There are a lot of things different about humans. Our hairlessness, our pronounced sexual dimorphism (pendulous breasts on non-nursing females), our brains, our posture, the lack of a penile bone in males (other primates have them), the helplessness of our babies, our relative physical weakness, etc... and we don't have a lot of the answers as to why these things are the way they are."

I respond that the aquatic theory explins many of these "things different about humans".

It's a fun theory. Your questions are fair tests of its viability.


100 posted on 12/08/2006 11:46:14 AM PST by StructuredChaos (Disorder is but misunderstood order; Order is naught but chaos structured.)
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