EVOLUTION OF THE HUMAN BODY POSTURE

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Offline GBSB

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EVOLUTION OF THE HUMAN BODY POSTURE
« on: 21/06/2006 22:28:55 »
EVOLUTION OF THE HUMAN BODY POSTURE

As long as we can trace the history of human beings, we can see that there were two main activities which were necessary to perform in order for humans to be able to survive.  
One of these activities was moving from one place to another (walking, running or jumping).
Another activity was to carry goods (mainly in the hands or on the shoulders.)
Like no other species, humans were carrying goods mainly on the shoulders and in the hands.
 
Till recently, human’s rarely traveled, even for small distances, without carrying some goods in the hands or on the shoulders.

The two main things that human beings had to take care of when moving (walking, running and occasionally jumping) from one place to another was, where he is stepping and how he is transferring body weight from one leg to another, with the intention not to hurt the surface of the bottom of the feet and not to lose balance (if he losses balance, he will fall on the ground). Because of that, he was transferring his body weight form one leg to another carefully and independently from the speed of the movement.
 
These two activities (traveling and at the same time carrying goods on the shoulders and/or in the hands) have big influences in forming the body posture. Because of that, the way of the body posture, from the bottom of the feet to the top of the shoulder, has evolved to be able to carry goods in the hands and on the shoulders, and at the same time be able to maintain balance.
 
Carrying the goods was one important activity which guided the evolution of the human body posture.
 
By doing this activity, the environment demanded from the human to see where he was going and where he was stepping.
The holding of the head and the neck has developed in such a way that he can with a minimum movement of the head, to see where he is stepping and where he is going. Because of that, his neck and head was slightly leaning forward.
For example, when walking through a forest, we need to be able to see where we are going and where we are stepping. The time span between looking in the direction where we are going and looking on the ground where we are stepping must be short. Because if we watch for too long where we are stepping, we will in a short time hit the tree and if we watch too long where we are going, we will in a short time trip on the birch or some other objects which is lying on the ground. As we change our focus in a short time, from where we are going and where we are stepping, the head and the neck from itself starts to lean slightly forward to enable us to see where we are going and where we are stepping, by mainly just moving our eyes with a minimum movement of the head.

If we walk through a forest without carrying some weight in the hands and on the shoulders, we can still do that with the many different types of body postures, concerning the body from the bottom of the feet to the top of the shoulders.
 
But if we carry some weight on the shoulders, or in the hands, in the long term we can do this activity only if our body from the bottom of the feet to the top of the shoulder is in an upright position and the neck with the head is in a relaxed slightly forward leaning position.
 
Carrying some goods on the shoulder and in the hands was an important contributing factor in gaining and maintaining physical strength and physical balance of the human body, and it was also a contributing factor in the evolution of the human race.  





« Last Edit: 10/12/2006 20:08:06 by GBSB »

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Offline tony6789

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #1 on: 23/06/2006 21:46:35 »
actually there r hunchbacks



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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #2 on: 26/06/2006 16:57:46 »
I wonder what caused a particular species of ape to evolve an upright posture in the first place and what was the driving evolutionary force that totally changed the hip bone of this particular species.

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #3 on: 26/06/2006 17:00:27 »
PS
All the other apes survived without walking upright so it was not a survival response.

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Offline neilep

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #4 on: 26/06/2006 17:36:02 »
This is an interesting topic.

I would have thought that it was a necessity for us to stand upright was at least two fold.

1. Being upright is an invaluable ability for protection from being hunted

2. In contrast , being upright is a distinct advantage when it comes to hunting as the taller you are the further you can see unsuspecting dinner !!

..additionally, being upright helps to serve to reach higher fruits from trees etc.

Walking upright was probably one of the main landmarks that set us apart from the other apes. This must have contributed enormously to the manner in which our evolution was affected.



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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #5 on: 26/06/2006 17:44:56 »
quote:
Originally posted by GordonP
I wonder what caused a particular species of ape to evolve an upright posture in the first place and what was the driving evolutionary force that totally changed the hip bone of this particular species.



Caused or allowed?

The normal assumption about evolution is that it is caused by random mutations, and some of these random mutations then prove to be useful in certain niches and this allows the mutated individuals to survive and thrive, and thus create a new species based upon those mutations.

First question – what are the disadvantages of a bipedal stance, and why have the other apes not taken it up?

One obvious disadvantage is the need for relatively flat feat that are convenient when one walks on flat ground, but would be problematic when climbing trees.  Humans have not only flat feet, but relatively flat hands, which again makes the hands more flexible in many ways, but although the hands can be used to grip branches, they probably need more effort to do so because their relaxed state is to be almost flat palmed.

A long, upright, body also exposes much of the front of the body to attack in a way that a body walking on four limbs does not.  On the other hand, a long upright body allows one to see further over open ground, as well as being more streamlined in the water.



George

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #6 on: 26/06/2006 19:39:35 »
quote:
Originally posted by neilep

This is an interesting topic.

I would have thought that it was a necessity for us to stand upright was at least two fold.

1. Being upright is an invaluable ability for protection from being hunted

2. In contrast , being upright is a distinct advantage when it comes to hunting as the taller you are the further you can see unsuspecting dinner !!

..additionally, being upright helps to serve to reach higher fruits from trees etc.

Walking upright was probably one of the main landmarks that set us apart from the other apes. This must have contributed enormously to the manner in which our evolution was affected.



Men are the same as women, just inside out !



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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #7 on: 26/06/2006 19:40:28 »
1 Why?

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #8 on: 26/06/2006 19:42:58 »
2 seeing dinner is one thing, eating it another. Addtionaly climbing trees allows you to feed near the top of the tree.

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #9 on: 26/06/2006 19:47:07 »
Hi George
Humans evolved flat feet, presumably while they were evolving a pelvic bone that allowed them to stand upright. Why?

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Offline neilep

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #10 on: 26/06/2006 19:52:43 »
Hi Gordon,

Standing upright doesn't preclude you from climbing trees still !

To answer your query and these are just my own conclusions, but standing upright enables you to see predators from farther away and also to peer down into high grass to see squatting predators about to pounce !...in my opinion of course....so you get an early warning..

...and seeing dinner from further away , I would have thought would expand your chances of seeking dinner, due to the wider field of view....but as I said..these are just my thoughts.....

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #11 on: 26/06/2006 20:30:13 »
Hi Neilep
Standing upright offers no advantages over an ape sitting high in a tree.

The question is. Why did one particular species of ape abandon the safety of the trees for a life on the ground? Remember although evolution, given the right circumstances, can happen comparitively quickly, this species of ape must have survived on the ground for thousands of years before the transformation of the pelivic bone was complete. How did this species survive for long enough for the process to reach completion?

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #12 on: 26/06/2006 20:44:50 »
quote:
Originally posted by GordonP

Hi Neilep
Standing upright offers no advantages over an ape sitting high in a tree.

The question is. Why did one particular species of ape abandon the safety of the trees for a life on the ground? Remember although evolution, given the right circumstances, can happen comparitively quickly, this species of ape must have survived on the ground for thousands of years before the transformation of the pelivic bone was complete. How did this species survive for long enough for the process to reach completion?

G W Pipes



One would presume because proto-human suddenly found himself in a place that lacked trees, so the choice of running up a tree for safety simply did not occur.

Could be climatic change that reduced trees; could be overcrowding that forced some apes out of the forest; or it could be some calamity that left some proto-humans stranded away from their traditional habitat.



George

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Offline neilep

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #13 on: 26/06/2006 20:48:57 »
Hi Gordon (nice homepage..I'll have to read that when I get a chance..but it looks fascinating !..see ?...everybody will look at it now !! [:D])...oh !..call me Neil !

You ask a very good question...I just wish I had an answer to complement it [:)]

I just do not know......circumstance and necessity leads to invention  and evolution...something must have happened to a breed of ape that ,where ever they were located on Earth at the time, the surrounding geography must have imposed/coerced this evolutionary progress which, must have been specific to that area ..it must have dictated over time the evolution of the ability to stand upright....

without the benefit of a time machine I guess we'll never know unless irrefutable proof is discovered.

Do you have any theories on the matter ?

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« Last Edit: 26/06/2006 20:57:15 by neilep »
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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #14 on: 26/06/2006 20:51:39 »
quote:
Originally posted by GordonP
2 seeing dinner is one thing, eating it another. Addtionaly climbing trees allows you to feed near the top of the tree.

G W Pipes



Rather depends upon what you consider to be dinner.

If your happy eating fruit and veg, then the top of a tree is fine, but if you want some meat in your diet, then there is a limit to what you can have at the top of the tree.

Even Chimpanzees rather like a mixed diet, although Gorillas seem to be happy with a strictly vegetarian diet, with a few insects (although, interestingly gorillas are rather large for climbing trees).



George
« Last Edit: 26/06/2006 20:58:28 by another_someone »

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #15 on: 26/06/2006 20:57:59 »
I don't think so George, the climatic change that affected North Africa when the sub-continent of India came into contact with Ero-Asia must have happened slowly enough for all the apes to follow the retreating trees into central Africa. We are still talking about a massively large area of jungle, big enough for all the apes.

Why did our ancestors stay behind? And how did they survive long enough to evolve into the human species?



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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #16 on: 26/06/2006 21:04:06 »
Meat eaters are, by and large, preditors. Preditors are, by and large top of the food chain. How did an ape get there?

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #17 on: 26/06/2006 21:32:42 »
quote:
Originally posted by GordonP

I don't think so George, the climatic change that affected North Africa when the sub-continent of India came into contact with Ero-Asia must have happened slowly enough for all the apes to follow the retreating trees into central Africa. We are still talking about a massively large area of jungle, big enough for all the apes.

Why did our ancestors stay behind? And how did they survive long enough to evolve into the human species?

G W Pipes



Speciation does not happen across a continent.  In order for a new species start out, it has to occur in a very small geographic area.  Even if the mass of apes were to be able to follow the retreating trees, one would expect individual communities to become separated from the mass retreat.

Nor can it be said that there is ever enough forest/jungle for all the apes.  The nature of all species is that they will expand their population to utilise all the resources at their disposal.  Since it is the nature of the ecosystem that there are times when available resources are increasing (allowing an increase in population), and times when resources reduce (causing pressure on the population).  It would thus seem perfectly normal that in one of these period of expanding resources, the population of apes would expand to utilise these resources; but then when resources started to become more restricted, some of this large population of apes suddenly found they did not have the resources to live on, and had to look for new resources.

The Indian subcontinent actually started colliding with Asia around 55 million years ago, long before the proto-humans separated from other apes.  Apes themselves only separated from other monkeys around 25 million years ago, and humans from other apes about 7 million years ago.  Over those 7 million years, there have been many changes in climate, for all sorts of reasons, many of which are not even fully understood.  I don't know what was the direction of global climate change, let alone local climate change, was at the time when proto-humans separated from other apes.



George

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #18 on: 26/06/2006 21:41:15 »
quote:
Originally posted by GordonP
Meat eaters are, by and large, preditors. Preditors are, by and large top of the food chain. How did an ape get there?



So fasciitis necroticans or Clostridium botulinum are at the top of the food chain?

I think it is a little simplistic to look at the 'food chain' as a structure that has a clear top and a clear bottom.

This is ofcourse even further complicated by animals that indulge in cannibalism (which includes both some human tribes and chimpanzees).  Are animals who eat their own kind above or below themselves in the food chain?



George
« Last Edit: 26/06/2006 21:41:49 by another_someone »

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #19 on: 26/06/2006 22:14:40 »
Hi again George
Where ever, or when ever, apes began to walk upright, it happened. Even Darwin couldn't tell us why. In 2006 one-one else can.

How does an ape, so dependent on trees for survival, suddenly survive on the open grasslands?

One possible answer to this question is so politically incorrect, so soaked in sex and violence, that I hesitate to offer it before properly examining other explainations.

Please help me out, offer me an explaination.

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #20 on: 26/06/2006 22:49:18 »
quote:
Originally posted by GordonP
How does an ape, so dependent on trees for survival, suddenly survive on the open grasslands?



Animals can change there decencies and relationships quite dramatically.

Giant pandas are related to bears, and yet bears are carnivores while Giant Pandas have a very close dependence upon bamboo.  How is this change of dependency any less unusual than the change of ape from forest dwelling to living on a savannah or in a coastal area (both of which have been suggested as possible environments for proto-humans)?

We don't know exactly what the change in environment allowed the change in proto-human physiology, but there is nothing so unusual in such a change that it has not been seen in many other species.

What the exact dependency between pre-human apes and the forest were is itself not totally certain.  Gorillas, although they are forest dwellers, are not themselves tree climbers, although most other apes are.

http://en.wikipedia.org/wiki/Mountain_Gorilla
quote:

Mountain Gorillas have longer and darker hair than other gorillas, enabling them to live at high altitudes and travel into areas where temperatures drop below freezing. They have adapted to a life on the ground more than any other non-human primate, and their feet most resemble those of humans. Gorillas can be identified by nose prints unique to each individual. Researchers often use photographs and illustrations of noses for identification and monitoring.



http://en.wikipedia.org/wiki/Sahelanthropus%5Ftchadensis
quote:

The fossil skull TH 266, nicknamed "Toumaï" ("hope of life" in the local Goran language of Chad), may be a common ancestor of humans and chimpanzees; most molecular clocks suggest humans and chimps diverged 1–2 million years after S. tchadensis (5 mya). The original placement of this species as a human ancestor but not a chimpanzee ancestor complicated the picture of the human family tree. In particular, if Toumaï is only a direct human ancestor, its facial features bring the status of Australopithecus into doubt because the thickened brow ridgers are similar to later hominids, but not earlier ones. Another possibility is that Toumaï is anatomically related to both humans and chimpanzees, but the ancestor of neither. Brigitte Senut, the discoverer of Orrorin tugenensis, claims that the features of S. tchadensis are consistent with a female proto-gorilla.
If Senut's claims are true the find would be especially significant; there have been no chimp or gorilla ancestors to be found anywhere in Africa and light would be shed on their family trees. What the find does show is that the last common ancestor of humans and chimpanzees is unlikely to resemble chimpanzees very much, as had been previously supposed.



The emphasis on the last paragraph is mine, but I think it is important to remember that our common ancestor with the other great apes was no more chimpanzee, or gorilla, than it was human; but was another animal altogether.

quote:
Originally posted by GordonP
One possible answer to this question is so politically incorrect, so soaked in sex and violence, that I hesitate to offer it before properly examining other explainations.



No doubt sex and violence comes into it somewhere – these are forces that are very prevalent in the world around us, and play no small part in evolution.



George
« Last Edit: 26/06/2006 23:20:56 by another_someone »

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #21 on: 27/06/2006 00:19:25 »
You might wish to have a look at another similar discussion about the separation of human from ape, although not singling out the issue of the upright stance, but may have some bearing on it.  It included a very highly speculative story by me as to how a hypothetical situation could have arisen that would have created such a division, including different physiology and very different adaptations to different environments.  It does not claim to in any way be a definitive answer to the question, merely a speculation about a possible (and grossly simplified) scenario that could be regarded as a model for the type of thing that could have lead to that outcome.

http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=2811#28058




George

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #22 on: 27/06/2006 20:31:35 »
Interesting discussion. Try this for another hypothetical senario.

The climate in North Africa starts to change, as the years pass the forest retreats to central Africa and all the apes, dependent on the trees for safe haven, retreat with the forest.

One particular species begin to spend most of their time on the fringes of the forest, already a user of tools (they use stones to break open nuts)they begin to scavenge on the remains of kills left by the preditors that now inhabit the open areas, using their tools to break open the bones which remain behind in order to get at the bone marrow.

They live in small family groups led by a dominant male, usually the biggest and strongest male. The groups comprise, the dominant male, several adult females, the young and several adult subordinant males. The dominant male regards the adult females as his wives and guards them from the other males. They are still reliant on the trees for safe haven from preditors and only venture onto the open ground while one of the group is in position high in the trees as a watchout.

So far nothing has happened to effect the evolution of the species.

One day a male is born with a slight mutation, nothing spectacular, just a deformation of the pelvic bone. He still moves about most of the time with his knuckles almost brushing the ground but he can do something none of the rest of the group can do, he can take many steps in an almost upright position, the rest of the group can manage only three or four steps in this position before dropping their hands to the ground. (As with many apes today).

Eventually he approaches maturity and driven by testosterone challenges the dominant male. Not yet fully mature his chances of success are practically nil and being something of a lightweight will probably always remain so.

As the two face each other he does something that has never been done before, he picks up a short stout piece of broken branch, stands almost upright and closes in on the dominant male who also stands almost upright in defiance. After a very short while dancing around the dominant male can stand upright no longer and drops his hands to the ground, he is now defenceless. The young male knocks seven bells out of him and takes over the harem.

Something new has happened, an ape has used a tool as a weapon, and changed the path of evolution. Now it is not the biggest and strongest who rules but the one who can stand upright the longest. As the ruler of the group has the females to himself his genes will predominate the next generation and so on and so forth.

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #23 on: 28/06/2006 17:43:16 »
quote:
Originally posted by GordonP

Interesting discussion. Try this for another hypothetical senario.

The climate in North Africa starts to change, as the years pass the forest retreats to central Africa and all the apes, dependent on the trees for safe haven, retreat with the forest.

One particular species begin to spend most of their time on the fringes of the forest, already a user of tools (they use stones to break open nuts)they begin to scavenge on the remains of kills left by the preditors that now inhabit the open areas, using their tools to break open the bones which remain behind in order to get at the bone marrow.

They live in small family groups led by a dominant male, usually the biggest and strongest male. The groups comprise, the dominant male, several adult females, the young and several adult subordinant males. The dominant male regards the adult females as his wives and guards them from the other males. They are still reliant on the trees for safe haven from preditors and only venture onto the open ground while one of the group is in position high in the trees as a watchout.

So far nothing has happened to effect the evolution of the species.

One day a male is born with a slight mutation, nothing spectacular, just a deformation of the pelvic bone. He still moves about most of the time with his knuckles almost brushing the ground but he can do something none of the rest of the group can do, he can take many steps in an almost upright position, the rest of the group can manage only three or four steps in this position before dropping their hands to the ground. (As with many apes today).

Eventually he approaches maturity and driven by testosterone challenges the dominant male. Not yet fully mature his chances of success are practically nil and being something of a lightweight will probably always remain so.

As the two face each other he does something that has never been done before, he picks up a short stout piece of broken branch, stands almost upright and closes in on the dominant male who also stands almost upright in defiance. After a very short while dancing around the dominant male can stand upright no longer and drops his hands to the ground, he is now defenceless. The young male knocks seven bells out of him and takes over the harem.

Something new has happened, an ape has used a tool as a weapon, and changed the path of evolution. Now it is not the biggest and strongest who rules but the one who can stand upright the longest. As the ruler of the group has the females to himself his genes will predominate the next generation and so on and so forth.

G W Pipes



As far as it goes, it does not seem impossible, but it does leave a good number of questions unanswered.

You have said that “Now it is not the biggest and strongest who rules but the one who can stand upright the longest“.  This seems fine, but does not explain why this was true of proto-humans, but not other apes.

Although it is true that over recent times, the advantage of human tools has been so overwhelming that other species of apes are now endangered species, but it does not explain why for so many millions of years the other apes continued to thrive in the face of these upright toolmakers.  One must assume that these other apes must have had their own advantages to their own way of life that undermined much of the advantage the upright toolmakers had (at least until very recently).  These advantages/disadvantages would have to be environmentally dependent, so the upright toolmakers thrived in one environment, while failing to make major inroads into the environment of the other apes.

Ofcourse, the obvious answer to this is that there is very little advantage to being able to run a long way while upright when the distance between trees is only a few steps away, and this may well have been why the toolmakers never (until recently) came to displace the non-toolmakers within the bounds of the forest itself.

The second issue is the difference between genetic drift and speciation.  In order for speciation to occur, you need a separate breeding population.  If the populations are not separated, then there will be interbreeding between populations before they have become sufficiently separated to form distinct and and separate species.  Ofcourse, one could add to your scenario that, not only has this tribe of apes moved to the edge of the forest, but this was not the main body of the forest, but a small island of forest in a sea of savannah; and as the forests retreat, so the island forest is shrinking, and the tree climbing apes are finding it ever more difficult to survive, and thus leaving the walking apes isolated.  Because most of these apes have been killed off, leaving only a very small residual population, you in fact have exactly the kind of genetic bottleneck that allows a new species to quickly take hold (i.e. the same situation that allows large numbers of genetic faults in a population to develop as the population inbreeds, so this is also the same mechanism that creates new species).





George

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Offline thebrain13

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #24 on: 29/06/2006 01:29:20 »
I think the key issue is defense. It's been brought up that taller creatures can see more prey, but on the flip side more predators can see you. if you look at when the dinosaurs roamed the earth you might notice that most of the carnivores walked upright, while most of the herbivores walked on all four. It makes since that a trex or a pack of velociraptors would trade being seen for the ability to find more prey, because what crazy creature is going to attack a pack of raptors or a trex. The diet is another advantage to walking upright. Herbivores need to eat a lot more then carnivores so they have more weight to carry around. If cows walked upright they would look like rosie odonell, and that is clearly not an efficient design. Herbivores can more adequatley defend and carry their weight around on all fours, where the more slender carnivores can afford walking upright. So my guess for the evolution of humans would be that somewhere down the line people seperated themselves from apes with intelligence first. With their bigger brains they were able to defend themselves better and could afford being seen more by other predators in exchange for being able to see more prey which led to developing the ability to walk upright. And with their new diet they could avoid looking like rosie.[xx(]

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #25 on: 29/06/2006 12:18:48 »
People didn't evolve from apes, we shared a common ancestor.
That common ancestor wasn't overly specialized for a life in either a forested or open environment. The ones that ended up living primarily in grasslands eventually became humans, the ones that lived in forests became monkeys.
 

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #26 on: 29/06/2006 13:18:34 »
quote:
Originally posted by xetho

People didn't evolve from apes, we shared a common ancestor.
That common ancestor wasn't overly specialized for a life in either a forested or open environment. The ones that ended up living primarily in grasslands eventually became humans, the ones that lived in forests became monkeys.



Technically, people did not evolve from apes because we are apes (most authorities now no longer make a distinction between apes and humans, regarding humans as merely another branch of the ape family).

I don't know of any evidence that exists as to the actual habitat that early apes (for they would have been apes, even if they were not Chimpanzees, Gorillas, or Humans) existed in; but there seems little reason to doubt that they would have been just as specialised for that environment as later apes (including Humans) are for theirs.

Apes never became monkeys.  Monkeys are a supergroup that includes apes.  Monkeys came first, and apes then became one of the branches from the monkey family, and humans became one of the branches of the ape family.



George

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #27 on: 29/06/2006 13:27:44 »
quote:
Originally posted by thebrain13

I think the key issue is defense. It's been brought up that taller creatures can see more prey, but on the flip side more predators can see you. if you look at when the dinosaurs roamed the earth you might notice that most of the carnivores walked upright, while most of the herbivores walked on all four.



This no doubt explains why giraffes and elephants are so short, and why kangaroos walk on all fours, or why lions walk on their hind legs.

quote:

The diet is another advantage to walking upright. Herbivores need to eat a lot more then carnivores so they have more weight to carry around.



This part is true, so carnivores tend to be sleeker, but they are no more likely to be bipedal (in fact, a bipedal cheetah would not run as fast).

Back to your issue of defence, there is one point that may be relevant, and that is communal defence.  Many social animals will post lookouts that give the social group an early warning of danger, and allow them time to prepare a communal defence against the threat.  For these animals, particularly given the high visibility that inevitably derives from having a large community of animals congregating together, early detection of a threat is more important that camoflage.



George

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #28 on: 29/06/2006 15:36:04 »
Revised senario.

First the facts, humans are apes but a different species from the Chimps etc. OK so far?

10/6 million years ago our direct ancestors were an unknown species of ape already split from the ancestors of Chimps etc. Still OK?

Hypothetical senario.

Climate change has created vast areas of grassland in Northern Africa. The forest and jungle has retreated to Central Africa and all the apes have stayed deep in, or on the fringes of the forest, where they are relitively safe from preditors.

Our direct ancestors, I'll call them "Ape type x" live in small family groups on the fringes of the forest. Each group is extremely territorial and any member of another group who strays into their territory is liable to get killed and eaten, unless the offender is female in which case she will be captured and added to the dominant male's harem.

In this way each group is relitively isolated from the other groups almost as if each was on a separate island.

Now let me original senario run.



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Offline thebrain13

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #29 on: 29/06/2006 19:20:17 »
quote:
Originally posted by another_someone

quote:
Originally posted by thebrain13

I think the key issue is defense. It's been brought up that taller creatures can see more prey, but on the flip side more predators can see you. if you look at when the dinosaurs roamed the earth you might notice that most of the carnivores walked upright, while most of the herbivores walked on all four.



This no doubt explains why giraffes and elephants are so short, and why kangaroos walk on all fours, or why lions walk on their hind legs.

quote:

The diet is another advantage to walking upright. Herbivores need to eat a lot more then carnivores so they have more weight to carry around.



This part is true, so carnivores tend to be sleeker, but they are no more likely to be bipedal (in fact, a bipedal cheetah would not run as fast).

Back to your issue of defence, there is one point that may be relevant, and that is communal defence.  Many social animals will post lookouts that give the social group an early warning of danger, and allow them time to prepare a communal defence against the threat.  For these animals, particularly given the high visibility that inevitably derives from having a large community of animals congregating together, early detection of a threat is more important that camoflage.



George



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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #30 on: 29/06/2006 19:31:32 »
i posted that on accident, i dont know how to do the quotes right. anyways to anothersomeone, my point on defense was if you can defend yourself you can afford to be seen. Ive never seen any creature try to attack full grown elephants and girraffes. And as far as the evolution of marsupials in australia, well thats another debate.

Lastly lets not forget that dinosaurs had much longer to evolve than mammals, the giant asteroid sent them back in evolution. walking upright is a more advanced feature. Im sure if there were raptors and giant tyrannosaurs walking the earth today, girraffes elephants and kangaroos would find themselves on the extinct list.

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #31 on: 29/06/2006 19:51:33 »
The main reason why apes started to stand upright was so that they could look over the fence into next doors garden to view the neighbours wife sun bathing !! [:D]

...actually..in all seriousness..though this link to a BBC site is not specifically about posture it does mention upright and standing tall a couple of times and is very interesting http://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/mother_of_man1.shtml

Men are the same as women, just inside out !
Men are the same as women, just inside out !

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #32 on: 29/06/2006 21:00:26 »
Hi Neil
I read about Lucy many years ago but in the book I read it was a man called Lakey who found Lucy.

No matter, it still confirms that Lucy, perhaps one of our ancestors, had evolved bipedal motion long before the evolution of the human brain.

The question is. What drove the evolution of the plevic bone and the bones in the feet in one particular direction, as George has pointed out evolution works best in isolated communities.

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #33 on: 29/06/2006 21:44:02 »
quote:
Originally posted by thebrain13
my point on defense was if you can defend yourself you can afford to be seen. Ive never seen any creature try to attack full grown elephants and girraffes. And as far as the evolution of marsupials in australia, well thats another debate.



Why are the marsupials another debate?

The point is that predator animals are just as keen not to be seen as prey species (it allows them to creep up on their prey all the better – many of the big sprinters can only last a short distance, and if the start their attack too early they will in all likelihood run out of puff before catching their prey – thus, it is often the predator who is more concerned about staying low than the prey).

quote:

Lastly lets not forget that dinosaurs had much longer to evolve than mammals, the giant asteroid sent them back in evolution.



This is totally incorrect, in a number of ways.

Proto-mammals separated from reptiles about 220 million years ago, but we all started from the same point in time, and had the same time to evolve to where we are today; we merely took different paths along the road of evolution.

Nor is there any notion of being more or less advanced, or having more time to evolve.  A species evolves to make the best use of its environment; but the environment we have today is different from any environment we had in the past, just as each moment of the past also had its own unique environment.  Neither reptiles, nor mammals, nor birds (who many consider the true descendents of the dinosaurs) have had that long to adapt to the current environment because the current environment has not been around for that long.

quote:

 walking upright is a more advanced feature.



It certainly is not the case that every species would benefit from walking upright, and in fact most bipedal animals are not that good at walking at all (but some of them are quite good at flying – since they have turned their forelegs into wings).

quote:

 Im sure if there were raptors and giant tyrannosaurs walking the earth today, girraffes elephants and kangaroos would find themselves on the extinct list.



I would doubt it.

The world is a lot cooler today than it was when the dinosaurs roamed the world, and secondly, the continents were bigger so there was more space for these giant animals to roam around.

Although there was clearly a catastrophe (very possibly an asteroid impact) that caused a major overhaul of species, but species change would have had to come about sooner or later, if only to adapt to the changes going on in plate tectonics and world climate.  These changes are constantly happening, and are constantly forcing changes in species.  All that these major catastrophes provide is a moment of accelerated change that allows the species the opportunity to play catch-up with the environment.



George

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #34 on: 29/06/2006 22:00:56 »
http://en.wikipedia.org/wiki/Australopithecus_afarensis
quote:

There are differing views on how Lucy or her ancestors first became bipedal full-time.
The so-called 'savanna theory' on how A. afarensis evolved bipedalism hangs on the evidence that around 6 to 8 million years ago there seems to have been a mass extinction of forest dwelling creatures including the oldest hominins recognizable: Sahelanthropus tchadensis and Orrorin tugenensis. This triggered a burst of adaptive radiation, an evolutionary characteristic that generates new species quickly. Lucy's genetic forebears were tree dwelling apes, but in Lucy's world the trees would have been much fewer, and Lucy would have been forced to find a living on the flat savanna. Being bipedal would have had evolutionary advantages. For example, with the eyes higher up, she could see further than quadrupeds. Bipedalism also saves energy. The disadvantages of bipedalism were great—Lucy was the slowest moving primate of her time, for example, but according to the hypothesis, the advantages of bipedalism must have outweighed the disadvantages.
There had previously been problems in the past with designating Australopithecus afarensis as a fully bipedal hominine. In fact these hominines may have occasionally walked upright but still walked on all fours like apes; the curved fingers on A. afarensis are similar to those of modern-day apes, which use them for climbing trees. The phalanges (finger bones) aren't just prone to bend at the joints, but rather the bones themselves are curved. Another aspect of the Australopithecus skeleton that differs from human skeleton is the iliac crest of the pelvic bones. The iliac crest, or hip bone, on a Homo sapiens extends front-to-back, allowing an aligned gait. A human walks with one foot in front of the other. However, on Australopithecus and on other ape and ape-like species such as the orangutan, the iliac crest extends laterally (out to the side), causing the legs to stick out to the side, not straight forward. This gives a side-to-side rocking motion as the animal walks, not a forward gait.
The so-called aquatic ape theory compares the typical elements of human locomotion (truncal erectness, aligned body, two-leggedness, striding gait, very long legs, valgus knees, plantigrady etc.) with those of chimpanzees and other animals, and proposes that human ancestors evolved from vertical wader-climbers in coastal or swamp forests to shoreline dwellers who collected coconuts, turtles, bird eggs, shellfish etc. by beach-combing, wading and diving. In this view, the australopithecines largely conserved the ancestral vertical wading-climbing locomotion in swamp forests ("gracile" kind, including Australopithecus afarensis and A. africanus) and later more open wetlands ("robust" kind, including Paranthropus boisei and P. robustus). Meanwhile, Plio-Pleistocene Homo had dispersed along the African Rift valley lakes and African and Indian ocean coasts, from where different Homo populations ventured inland along rivers and lakes. However, this theory is not taken seriously by anthropologists.





George

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Offline thebrain13

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #35 on: 30/06/2006 00:29:48 »
First off I think africa, asia, and europe are plenty big enough for dinosaurs to "Roam around" As for the world being cooler back then, so dinosaurs couldn't survive theory. I think thats false because unlike snakes, frogs, turtles, or modern day reptiles, many dinosaurs were warm blooded, and some had fur. And I know mammals had technically the same amount of time to develope as dinosaurs, but mammals specialized in being smaller, dinosaurs specialized in being humongous. Dinosaurs had more time to develope as the largest creatures on earth. Mammals relatively recently adopted that role. Your statement that all creatures wont benefeit from being bipedal, I agree with. As I pointed out before in the dinosaur world carnivores tended to be bipedal, herbivores tended to be four legged, and im sure there's a reason for that. But that wasn't always the case, early in dinosaurs developement all of them were four legged. As they became more and more advanced some adopted a bipedal stature, something that may happen to modern day mammals, given a few hundred milliion years.

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #36 on: 30/06/2006 02:26:01 »
quote:
thebrain13
I think the key issue is defense. It's been brought up that taller creatures can see more prey, but on the flip side more predators can see you. if you look at when the dinosaurs roamed the earth you might notice that most of the carnivores walked upright, while most of the herbivores walked on all four.



coming back to this point, it is wrong.

The Theropods (of which T. Rex is the best known) were bipedal, but did not walk upright.  As we both have agreed, these were the ancestors of modern birds (which are also bipedal), and they also had large tails with which to counterbalance, so they ran (if the were capable of running at all – top speed estimates between 11mph and 25 mph, depending upon assumptions made – although many of its more reptilian contemporaries would probably have been slower yet)  with their bodies parallel to the ground.

They were carnivores, although whether they were bipedal because it made them better carnivores, or whether they were carnivores because the energy requirements of bipedal locomotion demanded it, is another matter.

http://en.wikipedia.org/wiki/Tyrannosaurus_rex
quote:

Some argue that if Tyrannosaurus were a scavenger, another dinosaur had to be the top predator in the Amerasian Upper Cretaceous. Top prey were the larger marginocephalians and ornithopods. The other tyrannosaurids share so many characteristics that only small dromaeosaurs remain a choice as top predators. In this light, scavenger hypothesis adherents have hypothesized that the size and power of tyrannosaurs allowed them to steal kills from smaller predators.



The closest one can think of what T. Rex might have been capable of as a hunter might be the hunting behaviour of Secretary Birds.

http://en.wikipedia.org/wiki/Secretary_bird#Diet
quote:

The Secretary Bird is largely terrestrial, hunting its prey on foot, and besides the caracaras (such as Polyborus plancus) is the only bird of prey to do so habitually. Adults hunt in pairs and sometimes as loose familial flocks, stalking through the habitat with long strides. Prey consists of insects, small mammals, lizards, snakes, young birds, bird eggs, and sometimes dead animals killed in brush fires. Larger herbivores are not hunted, although there are some reports of Secretary Birds killing young gazelles.
Young are fed liquified and regurgitated insects directly by the male or female parent and are eventually weaned to small mammals and reptile fragments regurgitated onto the nest itself. The above foodstuffs are originally stored in the crop of the adults.
Secretary Birds have two distinct feeding strategies that are both executed on land. They can either catch prey by chasing it and striking with the bill or stomping on prey until it is rendered stunned or unconscious enough to swallow. Studies of this latter strategy have helped construct the possible feeding mechanisms employed by dinosaur-like terror birds that once walked the earth five million years ago.



But you will note that the Secretary Bird will only take on prey very much smaller than itself.

Ornithomimosauria, another bipedal  theropods, but much smaller, and faster, than T. Rex, was probably a herbivore, or at least an omnivore (these were the closest theropods to modern birds)..

quote:
thebrain13
many dinosaurs were warm blooded, and some had fur.



The theropods, which include all the bipedal carnivores you speak of, as far as I am aware in no cases had fur.  They probably were warm blooded, and at least the smaller ones probably had feathers, but the larger ones probably were more keen to dissipate heat effectively, and so dispensed with the feathers.

quote:
thebrain13
And I know mammals had technically the same amount of time to develope as dinosaurs, but mammals specialized in being smaller, dinosaurs specialized in being humongous. Dinosaurs had more time to develope as the largest creatures on earth. Mammals relatively recently adopted that role.



The earliest of the theropods, the Eoraptor, which was also a carnivore,but only about a meter tall, and 10 kilos in weight.

Changes in size are fairly easy and quick to change (just look at the diversity one can get in dogs, all within one species).

The problem with big animals is that they need a lot of feeding, and a lot of space.  I cannot really see T. Rex surviving in a dense forest – it would need open grassland or marshland (where its long hid legs would allow it to wade through the marshes, while its weight would have been less of a problem if it was partially submerged).



George

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #37 on: 30/06/2006 02:44:22 »
quote:
Originally posted by GordonP
Our direct ancestors, I'll call them "Ape type x" live in small family groups on the fringes of the forest. Each group is extremely territorial and any member of another group who strays into their territory is liable to get killed and eaten, unless the offender is female in which case she will be captured and added to the dominant male's harem.

In this way each group is relitively isolated from the other groups almost as if each was on a separate island.

Now let me original senario run.



What you describe is pretty much how chimps behave anyway.  It is not enough to create the level of isolation required.

The first question you have to ask is whether the changes are sex linked or not.  Since there is a sexual dimorphism in any species with regard to pelvic bone structure, there is little reason to believe that this change is linked to a sex gene.  Thus, even with the regular influx of females from the outside, it would still quickly dilute and genetic abnormality in the pelvic bone structure of Ape type x.

The other issue is that we do not know, and at present, have no reason to suspect, that full time bipedalism arrived at the time that the human lineage separated from the other apes.

If full time bipedalism did arrive at the same time that the two branches split - why did it happen then.  Was it merely coincidence, or was it a related factor.

For two species to split, you must create two distinct breading groups.  Clearly, geographic or environmental separation is the easiest and most obvious reason for two breading groups to separate, but then you would expect changes in physiology to follow the separation and not be coincident with it.

It is ofcourse possible that the separation of breading groups happens not because of geographic separation, but because the two groups find it difficult to interbreed.  Although we have been looking at bipedalism merely in terms of what advantages (and disadvantages) it brings to locomotion, what we have not looked at is how the changes in pelvic structure effect both child birth and sexual behaviour.



George

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #38 on: 30/06/2006 08:55:53 »
quote:

What you describe is pretty much how chimps behave anyway.  It is not enough to create the level of isolation required
.


The ancestors of chimps and the ancestors of my hypothetical type x lived different lifesyles. The chimps spent most of the time in the trees, where the use of a tool as a weapon offers no real advantages as both hands are needed to move quickly through the tree-tops. Type x spent most of the time on the ground where the ability to stand upright during combat with weapons offers massive advantages during a fight to establish who is the dominant male. The level of isolation required is maintained by cannibalism. Even as recently as a few hundred years ago cannibalism was practised by some humans.

quote:

The first question you have to ask is whether the changes are sex linked or not.  Since there is a sexual dimorphism in any species with regard to pelvic bone structure, there is little reason to believe that this change is linked to a sex gene.  Thus, even with the regular influx of females from the outside, it would still quickly dilute and genetic abnormality in the pelvic bone structure of Ape type x.


The mutation of the hip bone would not be diluted because of the power the dominant male held. As undisputed leader of the group he would father most if not all of the next generation. (Getting to close to one of his females while he was anywhere near would lead to a bad beating or could be fatal). With perhaps 4 or 5 breeding females in the group he could father many offspring, a fair percentage of which would carry the gene for mutated pelvic bone, both male and female.

When the next generation matured one of the males with the mutated gene would take his place. Within a few generations the mutated gene would be common to most of the group and only the male with the most extreme mutation would have an advantage in the fight to be the dominant male.

The influx of the odd captured females would not dilute the gene pool instead some of her offspring would inherit the upright gene.    







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« Last Edit: 30/06/2006 13:38:29 by neilep »
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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #39 on: 30/06/2006 14:26:22 »
quote:
Originally posted by GordonP
The ancestors of chimps and the ancestors of my hypothetical type x lived different lifesyles. The chimps spent most of the time in the trees, where the use of a tool as a weapon offers no real advantages as both hands are needed to move quickly through the tree-tops. Type x spent most of the time on the ground where the ability to stand upright during combat with weapons offers massive advantages during a fight to establish who is the dominant male. The level of isolation required is maintained by cannibalism. Even as recently as a few hundred years ago cannibalism was practised by some humans.
Quote

Gorillas also spend their entire life on the ground, because they are just too heavy to climb trees.  The difference is that they still live in the forest, so their visibility is limited, and everything they do is nearby.  They also are herbivores (with the exception of a few insects), so they don't need to run after their food, whereas Chimpanzees are omnivores who do chase and hunt other monkeys (and even have been observed to resort to cannibalism).

Quote
The mutation of the hip bone would not be diluted because of the power the dominant male held. As undisputed leader of the group he would father most if not all of the next generation. (Getting to close to one of his females while he was anywhere near would lead to a bad beating or could be fatal).



What happens in practice is that a male will hold on to a harem that is just as large as he can manage.  What in fact this means is that he does not quite manage to hold on to this size of harem, and quite often some of the females will sneakily wonder off for a quickie with some other male.  If the ground living apes and tree living apes can interbreed, there is no reason to assume that regular (if not frequent) interbreeding will not occur.  Either a tree living ape will come down to the floor, quickly mate, and rush back up into the trees where the ground living ape cannot follow; or a tree living male will quickly drop down to the ground (while the dominant male) is distracted elsewhere, have a quickie with one of the females, before disappearing back up into the trees.

Ofcourse, as I said, it depends upon whether the two groups can efficiently interbreed.

The different in posture does have significant implications for breading.  One different is ofcourse that humans are uniquely capable of mating face to face; but another difference is that all non-human female apes have a large pink vaginal swelling when they are on heat, whereas the upright posture of human females does not make that practical, and thus the ways in which a human male can tell if a human female is on heat must be different to that which most other apes use (humans use colour of cheeks and lips and size of breasts  as important cues; although both human and non-human apes can still use smell, and ofcourse behavioural changes).  If a male cannot properly tell that a female is on heat, then he will be less motivated to mate with her, and thus simply changing the cues for mating can often be enough to separate two groups into distinctly separate breeding groups.

Ofcourse, none of this explains how one group became habitually tree living and another habitually ground living if they shared the same space, and were still interbreeding (what we have explained is that once they were separated into these two groups, they may not easily reintegrate – but the separation had to come about first, and this would most logically still require geographic isolation of a very small group).



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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #40 on: 30/06/2006 16:39:26 »
No-one in this thread has put forward the temperature regulation argument for an upright posture:-

" Many mammals have complex chambers with moist linings in the nose and a heat exchange system to keep the blood cool as they pant to speed up evaporation. This was not an option for early hominids as they did not have a muzzle in which to house a cooling system. However, an upright posture would solve many of the problems, especially combined with a reduction in body hair. Upright walking means that less of the body surface is exposed directly to the sun at midday, while heat can be lost faster and any breezes are more likely to cause evaporation of sweat and so cool the body down. Retaining hair on the top of the head and perhaps the shoulders acts as a shield for the areas directly exposed to the sun.

An improved ability to control body temperature would mean that our ancestors could forage around midday, when there was less competition and fewer predators nearby. If this is correct, hair loss probably occurred relatively early in evolution, and is linked to bipedalism. "
http://www.fortunecity.com/emachines/e11/86/human.html
 
 
« Last Edit: 30/06/2006 16:43:31 by ROBERT »

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #41 on: 30/06/2006 17:08:49 »
What I envisage is a group of apes that are extremely territorial and permit no other apes in their territory, neither tree dwellers or ground dwellers.

Each group of type x won't permit intrusion by members of other type x groups or even tree dwelling type y's or z's, the penalty is to be eaten.

Of coarse the dominant male will have to be constantly watching the other males in his group and will not always be successful in preventing the odd meeting. However as I said it is sufficient for him to father MOST of the next generation, that way a significant number of the next generation will inherit the mutated gene. After a few generations the mutated gene will have spread through the majority of the population, males and females alike,as the dominant ape is almost certainly going to possess the mutated gene.

A few more generations and every member of the group will possoss the gene. Then the biggest and strongest ape will once again become the dominant ape until another mutation happens allowing one individual to remain upright for even longer than the rest.

Darwin said that evolution is very much like the life of a soldier, long periods of time pass when nothing much happens, interspersed with short periods of frantic activity.

The evolution of bipedel motion would have been one such short period of frantic activity and with my sex and violence theory COULD have happened in perhaps a few hundred generations. Overnight in evolutionary terms.

     



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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #42 on: 30/06/2006 17:46:12 »
quote:
Originally posted by GordonP
What I envisage is a group of apes that are extremely territorial and permit no other apes in their territory, neither tree dwellers or ground dwellers.

Each group of type x won't permit intrusion by members of other type x groups or even tree dwelling type y's or z's, the penalty is to be eaten.



You are also assuming an efficiency that does not exist in nature.

The fact is that tree dwelling apes will always have a quick escape available from the ground dwelling aped, and actually do not have that much to fear from them, unless they get particularly sloppy.  In fact, I would so so far as that if a troop of tree dwelling apes felt threatened by a ground swelling ape, collectively they probably would have little difficulty in dispatching it  (one tree dwelling ape creates a distraction to draw the ground dwelling ape into a trap, while the others drop ontop of him and overwhelm him with their numbers (even if the tree dwellers were smaller, as they probably would be, they could not be that much smaller if they still able to interbreed, and a ground dweller would never fight off a troop of 4 or 5 tree dwellers once they have landed ontop of him).

quote:

Of coarse the dominant male will have to be constantly watching the other males in his group and will not always be successful in preventing the odd meeting. However as I said it is sufficient for him to father MOST of the next generation, that way a significant number of the next generation will inherit the mutated gene. After a few generations the mutated gene will have spread through the majority of the population, males and females alike,as the dominant ape is almost certainly going to possess the mutated gene.



But why would the dominant male always have the mutated gene?

Firstly, if a mutated male breads with an unmutated female, there is only a 50% change that the offspring will carry the mutated gene, thus both genes would continue to survive in the population in perpetuity (the exact percentage of the population carrying the gene may vary, depending on the advantages the gene bring; but it will neither will ever actually be eradicated from the population).

Secondly, if the ground dwellers and tree dwellers can interbreed, then even if the gene holds a benefit to the ground dwellers, it actually hold a disadvantage to the tree dwellers (if this were not the case, and if we accepted the simplistic suggestion that the gene that was less advantageous would have died out, then the tree dwellers would have died out, and we know this is not the case, they simply formed a separate breading population).  Thus, there would be a ready pool of unmutated genes still able to interbreed with the mutated genes, and each would be in constant competition with the other throughout the combined population of tree and ground dwellers.

quote:

Darwin said that evolution is very much like the life of a soldier, long periods of time pass when nothing much happens, interspersed with short periods of frantic activity.

The evolution of bipedel motion would have been one such short period of frantic activity and with my sex and violence theory COULD have happened in perhaps a few hundred generations. Overnight in evolutionary terms.



With this I agree with (except that I am not aware that Darwin actually said that, since I thought it to be a post Darwinian concept), it is the question of whether it could have happened within a population that was still in the geographic proximity of the larger population that I disagree with.

As I said, it is also still open to question whether the separation of mainstream apes from humans happened synchronously with the advent of full time bipedalism, or whether they happened at different times.  It may have been, in my view, either possibility.



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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #43 on: 30/06/2006 17:53:57 »
quote:
Originally posted by ROBERT

No-one in this thread has put forward the temperature regulation argument for an upright posture:-

" Many mammals have complex chambers with moist linings in the nose and a heat exchange system to keep the blood cool as they pant to speed up evaporation. This was not an option for early hominids as they did not have a muzzle in which to house a cooling system. However, an upright posture would solve many of the problems, especially combined with a reduction in body hair. Upright walking means that less of the body surface is exposed directly to the sun at midday, while heat can be lost faster and any breezes are more likely to cause evaporation of sweat and so cool the body down. Retaining hair on the top of the head and perhaps the shoulders acts as a shield for the areas directly exposed to the sun.

An improved ability to control body temperature would mean that our ancestors could forage around midday, when there was less competition and fewer predators nearby. If this is correct, hair loss probably occurred relatively early in evolution, and is linked to bipedalism. "
http://www.fortunecity.com/emachines/e11/86/human.html



The issue of protection from the Sun is more of an issue on open savannah than it is in forest conditions.

It is certainly true that many mammals pant to release heat, but equally many others do not.

The point is, whether we are talking about heat regulation, or predator avoidance; there had to be a local environmental change that forced one groups of apes to become bipedal, while another group remained arboreal.  Clearly, this had to be a change in the environment, otherwise bipedalism would have happened earlier.  Clearly it could not have effected everywhere, otherwise no ape would have remained  arboreal.



George

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #44 on: 30/06/2006 19:34:19 »
quote:

"You are also assuming an efficiency that does not exist in nature."
.

On the contrary, many animals have clearly defined territories which they guard jealously.


quote:

"But why would the dominant male always have the mutated gene"?


Because the mutated gene gives an obvious advantage in a fight for the right to be dominant male.
quote:

"Firstly, if a mutated male breads with an unmutated female, there is only a 50% change that the offspring will carry the mutated gene, thus both genes would continue to survive in the population in perpetuity (the exact percentage of the population carrying the gene may vary, depending on the advantages the gene bring; but it will neither will ever actually be eradicated from the population)".


True if we are talking about one mating but if the mutated male has almost inclusive rights to all the females in the group then we are talking about 50% of the next generation carrying the gene. He maintains almost exclusive rights because of the advantage he has in personal combat due to his mutated gene. His successor in the next generation will almost certainly carry the gene and have the same advantage. When he starts mating with his generation of females 50% of them will also be carrying the gene, so any mating such a female will result in 100% of the offspring carrying the gene and 50% of his offspring will carry the gene when mating with a female that does not carry the gene. Therefore 75% of the next generation will carry the gene. Allowing for the odd bit of hanky-panky by the other males, 50% of which will be carrying the gene anyway, let's say 60% of the second generation. By the 4th or 5th generation the gene will be carried by 99% of the group.

 

quote:

Darwin said that evolution is very much like the life of a soldier, long periods of time pass when nothing much happens, interspersed with short periods of frantic activity.


I believe I read that in "Origin of the species" or it may have been in "The descent of man". Also the quote may not be word perfect but the meaning is clear.





G W Pipes
« Last Edit: 30/06/2006 20:36:02 by neilep »
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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #45 on: 01/07/2006 01:43:44 »
quote:
Originally posted by GordonP

quote:

"You are also assuming an efficiency that does not exist in nature."
.

On the contrary, many animals have clearly defined territories which they guard jealously.



But never 100% successfully.

quote:

quote:

"But why would the dominant male always have the mutated gene"?

Because the mutated gene gives an obvious advantage in a fight for the right to be dominant male.



Obviously not in every situation, otherwise there would never have survived any non-mutated genes.

The problem is that it is not enough to show how ape x survived, you must also demonstrate a situation where both ape x and ape y survive, and yet they remain as separate species.  Simply arguing that you believe you have found a way that would cause ape x to triumph over the inferior ape y will not suffice.

quote:

True if we are talking about one mating but if the mutated male has almost inclusive rights to all the females in the group then we are talking about 50% of the next generation carrying the gene. He maintains almost exclusive rights because of the advantage he has in personal combat due to his mutated gene. His successor in the next generation will almost certainly carry the gene and have the same advantage. When he starts mating with his generation of females 50% of them will also be carrying the gene, so any mating such a female will result in 100% of the offspring carrying the gene and 50% of his offspring will carry the gene when mating with a female that does not carry the gene. Therefore 75% of the next generation will carry the gene. Allowing for the odd bit of hanky-panky by the other males, 50% of which will be carrying the gene anyway, let's say 60% of the second generation. By the 4th or 5th generation the gene will be carried by 99% of the group.



But this does not work as simply as that.  There are many deleterious inheritable genes in existence in the human population, and yet despite the fact that they should reduce reproductive efficiency for the individual, a small percentage of humans still keep getting born with those genes.  The fact that the gene is deleterious ensures that its frequency remains low, but it is never totally eradicated from the population (and this remains true as long as the population remains large).
 

quote:

quote:
Originally posted by GordonP
Darwin said that evolution is very much like the life of a soldier, long periods of time pass when nothing much happens, interspersed with short periods of frantic activity.


I believe I read that in "Origin of the species" or it may have been in "The descent of man". Also the quote may not be word perfect but the meaning is clear.



http://en.wikipedia.org/wiki/Punctuated_equilibrium
quote:

Punctuated equilibrium (or punctuated equilibria) is a theory in evolutionary biology which states that most sexually reproducing species will show little to no evolutionary change throughout their history. When evolution does occur, it happens sporadically (by splitting) and occurs relatively quickly compared to the species' full duration on earth. Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which hypothesizes that most evolution occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis).

Punctuated Equilibrium's History


Punctuated equilibrium originated as an extension of Ernst Mayr's concept of genetic revolutions by peripatric and allopatric speciation. Although the workings of the theory were proposed and specifically identified by Mayr in 1954, most historians of science recognize Niles Eldredge and Stephen Jay Gould's 1972 paper as the principal source of its acceptance (by both paleontologists and evolutionists) and as the foundational document of a new and serious paleontological research program (Mayr 1992: 25-26, Shermer 2001: 102-113). Punctuated equilibrium differed from Mayr simply in that Eldredge and Gould had placed considerably greater emphasis on stasis, whereas Mayr was generally concerned with explaining the morphological discontinuity (or punctuational patterns) found in the fossil record.
The Eldredge and Gould paper[1] was presented at the Annual Meeting of the Geological Society of America in 1971. The symposium focused its attention on how modern microevolutionary studies could revitalize various aspects of paleontology and macroevolution. Tom Schopf, who organized that year's meeting, assigned Stephen Jay Gould the topic of speciation. Gould recalls that "Eldredge's 1971 publication [on Paleozoic trilobites] had presented the only new and interesting ideas on the paleontological implications of the subject—so I asked Schopf if we could present the paper jointly." (Gould 2002: 775) They did. According to Gould "the ideas came mostly from Niles, with yours truly acting as a sounding board and eventual scribe. I coined the term punctuated equilibrium and wrote most of our 1972 paper, but Niles is the proper first author in our pairing of Eldredge and Gould." (Gould 1991)



The idea you speak of only came to the for around 1954.



George

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #46 on: 01/07/2006 08:57:04 »
I have over simplfied the theory in order to save typing.

Of course a group will never defend it's territory with 100% success but it is not neccessary for the group to be totally isolated. Indeed I have said that the gene pool may have been affected by capured females. This will not matter in the long run.

Point two. The mutated gene does not have to offer an advantage in every situation. But only in a fight to be dominant male. In such a situation the ability to stand upright longer than your opponant offers a massive advantage when you have a weapon like a baseball bat in your hand. Even if the other male picks up such a weapon his inability to stand upright for more than a few steps makes the weapon almost usless. The male with the mutated gene will win every time.

x and y. After many generations x is walking almost upright most of the time. They still eat almost anything edible. x eats y.

Despite the comlexities of reproduction it is neccessary only for the ape with the mutant gene to father a significant number of the next generation. As one of the next generation with the gene will become dominant male (as I have explained above) the gene will quickly dominate the gene pool. We are talking about a group with a population of perhaps 15 to 20, or less.

Regarding the Darwin quote, it doesn't really matter where I read it.

G W Pipes
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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #47 on: 01/07/2006 10:49:49 »
quote:
Originally posted by GordonP
I have over simplfied the theory in order to save typing.

Of course a group will never defend it's territory with 100% success but it is not neccessary for the group to be totally isolated. Indeed I have said that the gene pool may have been affected by capured females. This will not matter in the long run.

Point two. The mutated gene does not have to offer an advantage in every situation. But only in a fight to be dominant male. In such a situation the ability to stand upright longer than your opponant offers a massive advantage when you have a weapon like a baseball bat in your hand. Even if the other male picks up such a weapon his inability to stand upright for more than a few steps makes the weapon almost usless. The male with the mutated gene will win every time.

x and y. After many generations x is walking almost upright most of the time. They still eat almost anything edible. x eats y.

Despite the comlexities of reproduction it is neccessary only for the ape with the mutant gene to father a significant number of the next generation. As one of the next generation with the gene will become dominant male (as I have explained above) the gene will quickly dominate the gene pool. We are talking about a group with a population of perhaps 15 to 20, or less.




The point is none of that addresses the issue of how both x and y survive, for the descendents of both branches are with us today.

Everything you have said so far has said that x will survive, and y will not – but that is not the situation we observe today.  In today's world, we have both the descendents of the homo branch of apes (designated as your x), and the other ape families (designated as your y).  In the real world, x did not universally triumph over y, nor y over x, but each has survived despite the other.  You have failed anywhere to explain how this mutual survival took place.

quote:

Regarding the Darwin quote, it doesn't really matter where I read it.



I agree, it matters not at all – it was just my going off at a tangent.



George
« Last Edit: 01/07/2006 10:50:25 by another_someone »

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Offline GordonP

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #48 on: 01/07/2006 12:43:19 »
Perhaps I've not made myself clear. I never intended to infer that all the apes disappeared, obviously the rest of the apes are still with us.

All am am trying to say is the within the group the apes with the mutation outbread those that did not posses it. And either infiltrated other similar groups with the same result or killed them.

G W Pipes
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Offline GBSB

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Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #49 on: 01/07/2006 21:17:10 »
I discovered why humans adopted bipedal stance.
I think it would be best to post it as new topic.
Please visit my new topic; “DISCOVERY-WHY HUMANS ADOPTED BIPEDAL STANCE”.

I will be glad to hear any comment and/or question

Luka Tunjic