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Author Topic: EVOLUTION OF THE HUMAN BODY POSTURE  (Read 29539 times)

Offline xetho

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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.
 

another_someone

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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
 

another_someone

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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
 

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.



G W Pipes
 

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


 

Offline thebrain13

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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.
 

Offline neilep

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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 !
 

Offline GordonP

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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.

G W Pipes
 

another_someone

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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
 

another_someone

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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
 

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.
 

another_someone

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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
 

another_someone

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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
 

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.    







G W Pipes
« Last Edit: 30/06/2006 13:38:29 by neilep »
 

another_someone

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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).



George
 

ROBERT

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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 »
 

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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another_someone

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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.



George
 

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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
 

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 »
 

another_someone

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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
 

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 »
 

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
 

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

 

The Naked Scientists Forum

Re: EVOLUTION OF THE HUMAN BODY POSTURE
« Reply #49 on: 01/07/2006 21:17:10 »

 

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