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

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

Origin Of Bipedalism Closely Tied To Environmental Changes

Champaign - May 01, 2002

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

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

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

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

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

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

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

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


TOPICS: Culture/Society; Extended News; Philosophy
KEYWORDS: godsgravesglyphs; humanevolution; origins; thelatesttheory
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Comment #21 Removed by Moderator

To: Maceman
"and like sushi" - That's funny.

Seriously, though, when our 2 kids were babies many years ago we taught them to swim before they learned to walk. We thought it was a necessity since we had a pool.

They actually learned to swim as babies very easily, though they could probably do it only fairly briefly.

22 posted on 05/29/2002 9:29:51 PM PDT by Sam Cree
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To: ex con
you are kidding, right?

No. Why do you ask? You think the "Naked Ape" thing really makes more sense? I have read Elaine Morgan's book, and it makes a very compelling case. After reading her book, it's hard to consider that anyonw would take Desmond Morris seriously. She really shoots holes in his theory.

23 posted on 05/30/2002 5:41:27 AM PDT by Maceman
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To: rmlew
Do you have a link?

Here is the link

24 posted on 05/30/2002 5:45:51 AM PDT by Maceman
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To: ex con
The aquatic theory makes a lot of sense to me, particularly after my health exam. My "bad" cholesterol is a bit high, so I have to decrease my intake of red meat, and increase my intake of omega-3 fatty acids, which are primarily found in fish. There are lots of indicators that the human diet optimally should include lots of seafood. Why would that be, unless our natural environment is near bodies of water?
25 posted on 05/30/2002 6:03:19 AM PDT by SauronOfMordor
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To: Patrick Henry; Quila; Rudder; Donh; VadeRetro; Radio Astronomer; Travis McGee; Physicist...
(((ping))))


26 posted on 05/30/2002 6:23:45 AM PDT by Sabertooth
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To: Maceman
I believe that the Aquatic Ape Theory is by far the most logical evolutionary explanation of the development of the human species.

Why can't humans swim from birth?

How can we be descended from aquatic apes, and have forgotten how to do that?




27 posted on 05/30/2002 6:29:12 AM PDT by Sabertooth
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To: Nick Danger
That fails the smell test.

Does it depend on your sense of smell?

28 posted on 05/30/2002 6:51:40 AM PDT by VadeRetro
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To: Salman; Sabertooth
I have a completely different idea. As far as I know, this is an original scientific hypothesis. To prove that I'm a crackpot, I've cast my hypothesis into the form of a sonnet:

Prometheus

Some theorize that man first walked erect,
To carry simple tools, or throw a spear,
The fossil record proves this incorrect:
Walking predates tools, two million years.

Others think that walking freed the hands,
To gather and to carry precious food,
But this selects the group and not the man,
And won't select at all when times are good.

I think 'twas fire that taught the ape to stand,
It's fearful, but it's pretty, warm and bright,
One stoopéd ape picked up a fire-brand,
And banished cold, and predators, and night.

Encumbered, thus unfettered, torch in hand,
An ape, tempered by fire, became a man.

29 posted on 05/30/2002 7:11:55 AM PDT by Physicist
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To: Physicist
To prove that I'm a crackpot, I've cast my hypothesis into the form of a sonnet:

Hey now!

Actually, I believe there's some merit to your theory...

Man evolved bipedalism to make fire and free their hands for shadow puppets.




30 posted on 05/30/2002 7:17:50 AM PDT by Sabertooth
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To: Sabertooth
Man evolved bipedalism to make fire

Actually, I believe that bipedalism helped the hominids to carry fire. Making it came much later, I believe.

Fire occurs naturally. There are parts of Africa that burn every year. There are many reasons why an intelligent creature would be attracted to fire: it's interesting to look at, it gives light and heat, it scares away predators, it kills and cooks animals that lie there to be consumed.

I imagine that our ancestors made a habit out of looking for fire and staying near it. After a while, the fire dies out, and they have to move on. But wait a minute: fires can be fed and kept alive. I'll bet a chimp can learn to do that. Furthermore, it can be carried around from place to place.

Ah, but now look: the ape with the torch has gained a very serious, immediate survival advantage. Sabertooths (no offense) are suddenly no problem. Walking and seeing at night, no problem. Impressing the ladies, well, naturally.

This, I believe, solves one of the great problems of the evolution of bipedalism: a half-bipedal creature doesn't make much sense. The survival advantage conferred by partial bipedalism has to be immediate and huge, to get "over the hump".

Tool use is one obvious thing that can do this, but first of all, hominids were walking several million years before their brains expanded, second of all, there's not much need to carry tools that can be obtained whenever needed (sticks and stones are everywhere), and third, use of the simplest stone tools (unfashioned rocks used as hammers) doesn't appear in the fossil record until well after bipedalism. (Recent discoveries put the gap at longer than the two million years in my sonnet, which I wrote two summers ago.)

So, I really think fire is it.

31 posted on 05/30/2002 7:39:39 AM PDT by Physicist
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To: Physicist
A couple of thoughts...

Chimps aren't fully bipedal, and make tools now.

But the rudimentary and disposable tools they make aren't likely to be the kinds of artifacts that archaeologists will find in a few million years.



32 posted on 05/30/2002 7:45:20 AM PDT by Sabertooth
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To: Sabertooth
Why can't humans swim from birth?

Why can't humans WALK from birth? Obviously, we must not be land animals.

Seriously, human infants can swim. I once saw a video of an experiment in which a young infant was put in water, and it instinctively began kicking and paddling with its arms. Apparently, this ability disappears rather quickly in an early child's development, unless it is nurtured. I understand that it disappears entirely after the first six months or so.

Moreover, the Aquatic Ape theory holds that we (obviously) never completed the transition to a purely aquatic species, like whales, or even sea lions.

33 posted on 05/30/2002 8:16:19 AM PDT by Maceman
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To: Maceman
Moreover, the Aquatic Ape theory holds that we (obviously) never completed the transition to a purely aquatic species, like whales, or even sea lions.

Glad you brought that up.

Have you noticed that only the fully aquatic cetaceans have shed their body hair? But isn't the aquatic lifestyle Elaine Morgan's explanation for why humans are almost hairless?

Further, we've got all kinds of fossils of the various families of aquatic mammals. Water is good for fossil-making.

Where are the aquatic ape fossils?




34 posted on 05/30/2002 8:24:13 AM PDT by Sabertooth
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To: Physicist
Hmmm. Does evidence for campfires (as opposed to natural fires) predate tools?
35 posted on 05/30/2002 8:29:13 AM PDT by VadeRetro
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To: Sabertooth
Have you noticed that only the fully aquatic cetaceans have shed their body hair?

If I recall correctly (I haven't read Elaine Morgan's book since 1969), she makes the point that other semi-aquatic animals, such as hippopotami, have also lost most of their hair.

Besides, we have not completely lost our hair -- certainly not to the point of dolphins and whales. Moreover, the hair that remains on us grows in patterns that are more consistently found in aquatic mammals that still have their hair. This pattern tends to follow the flow of water over the bodies of a forward swimming animal.

Now here's one for you -- how come none of the other primates cry salty tears, which is something only associated with aquatic mammals?

36 posted on 05/30/2002 8:38:19 AM PDT by Maceman
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To: Maceman
Moreover, the hair that remains on us grows in patterns that are more consistently found in aquatic mammals that still have their hair.

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

Now here's one for you -- how come none of the other primates cry salty tears, which is something only associated with aquatic mammals?

I don't know. Do otters have salty tears?

Are their non-aquatic non-primates with salty tears?

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

But we also don't have a single fossil of an aquatic ape.




37 posted on 05/30/2002 8:54:36 AM PDT by Sabertooth
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To: Sabertooth
BTW, are you just opposed to the Aquatic Ape theory because you favor the kind of Savannah Ape theory espoused by Desmond Morris, or because you oppose the idea of evolution altogether? Do you prefer the creation story of Genesis?

In any event, Regarding our ongoing debate about the Aquatic Ape, perhaps you will find this article -- particularly the part called "Interpreting the Power of Water" -- to be of interest. I did.

The Natural Child Project - All children behave as well as they are treated.


 

Releasing the Brakes with Water
(Excerpt from Chapter 15 of The Scientification of Love)
By Dr. Michel Odent

Learning from women

My own interest in the powerful influence of water on human beings developed at a time when I was exploring how the environment might influence the physiology of birth. It was apparent that many laboring women are attracted to water, wanting to have a shower or a bath. One day I went to a shop in the high street of our town and I bought an inflatable blue children's paddling pool.1 This was the beginning of the history of hospital birthing pools. As soon as the pool was installed I was faced with the most intriguing aspects of the human fascination with water. I could tell countless stories about laboring women whose attraction to water was so irresistible that they frustrated the best laid plans of the hospital staff. As soon as the tap was turned on, some of them could not wait to get into the pool and stepped in while there was no more than an inch of water in the bottom. The first lesson we learnt was that while the laboring woman is anticipating getting into the pool - hearing the noise of running water and seeing the blue water in a room that was painted blue with dolphins on the walls - it was as if a brake was already being released.

Beyond daily practice

Some time afterwards I began to realize how universal that tremendous attraction to water is during labor. In tropical countries, in places where quiet water was available, women often gave birth close to a river, or a lake or the sea. The aborigines of the west coast of Australia used to walk in shallow water before giving birth on the beach. It is probable that women relaxed and even gave birth in warm calm water in places as far apart as what is today called Columbia and Panama, some of the Polynesian islands, or some of the southern Japanese islands. It is also probable that in countries with non-tropical climates, the attraction to water in labor may have been stifled simply because hot and cold water from the tap was not available. However, this attraction could express itself in other subtle ways. At the beginning of this century, when most babies were born at home, the father used to spend hours boiling water. This ritual could be seen as an unconscious attempt to include water in the process of birth.

The similarities between the mysterious influence of water on the birth process and the erotic power of water are striking.2 It would take volumes to make an in depth study about the way in which the erotic power of water has been an inspiration to poets, painters, film makers, novelists, advertising agents, or restaurant owners, for example. And where do a young couple dream of going when they plan their honeymoon?

A watery environment also seems to beneficially affect the "milk ejection reflex". Certain breastfeeding advisers know how to take advantage of the sound of water. It can help women who have to express their milk with a breast pump if they do it in the shower. What is more, the "oceanic" feeling of mystical emotions is more likely to manifest itself on a beach, or by a river, or a lake.

Interpreting the power of water

It is easy to convince anyone of the mysterious effect of water on our human neocortical brakes. The real question is, Is this effect an aspect of our mammalian condition, or is our powerful relationship with water a specifically human trait? After all, all mammals, including the primates, spend their fetal life in water; yet there are some compelling reasons to claim that humans beings should be studied in depth from that point of view.

Today there is a tendency to consider Homo as a primate who adapted to living on the coast during certain phases of the evolutionary process. Any study of human nature should start from one fundamental and inescapable question : what sort of environment was homo originally adapted to?

In the case of other species of mammals in general - and primates in particular - it is easy to answer such a question. It is clear, for example, that the common chimpanzees were originally adapted to the African tropical forest and spent much of their time in the trees, while baboons adapted to the drier areas of Arabia and Africa and lived mainly on the ground. As for Homo, scientists can only offer hypotheses and theories.

In the current scientific context, it is well accepted that Homo separated from the other chimpanzees about six million years ago. Until recently, the favorite scenario was that our ancestors abandoned life in the trees to live on the open plain. According to the "Savannah" theory this change of habitat is the crucial factor that precipitated the emergence of Homo. Yet today there are many serious reasons to dismiss the "Savannah" theory - principally because the presumed period for the emergence of savannah conditions in Africa has been reassessed by new dating of the explosion of different species of hoof-footed mammals, pollen analysis, and closer examination of fossils of small mammals found in association with fossils of hominids.3 It appears that the emergence of the savannah occurred after the origin of the human family. Furthermore, we must bear in mind that the bones of our ancestor, the famous Lucy (Australopithecus Afarensis) were found eroding from the sand, lying among turtle and crocodile eggs and crab claws. And the bones of an older Australopithecus, found near Lake Rudolph in Kenya in 1995 were surrounded by many fossil vertebrates including fish and aquatic reptiles.4

We must also keep in mind that even though the human family emerged several million years ago, Homo Sapiens - the modern human being - is a young species. It is worth noticing that the oldest known footprints of a modern human being - dating back 117,000 years ago - have been found on the shore of a South African lagoon.

At the very time of the collapse of the "Savannah" theory, an alternative hypothesis - often called the Aquatic Ape theory -is gradually gaining ground and filling the gaps. Quite independently, Max Westenhofer in Berlin (as early as 1942)5 and Alister Hardy in Oxford in 19606 underlined that several of the differences between Homo and the other apes suggest an adaptation to a semi-aquatic environment. Since these pioneering works, the aquatic ape theory has developed and has been constantly updated thanks to the enthusiastic, creative and persevering work of Elaine Morgan.7,8,9 

Although, from a genetic perspective, we are a sort of chimpanzee (sharing 98.5% of our genes), dozens of features make us different from our close relatives. All these features are compatible with an adaptation to the coast.

Bipedalism - standing, walking and running upright - has been at the root of the theory from the beginning. Both Westenhofer and Hardy suggested that bipedalism was first adopted under duress, by ancestors of the human family confronted by the necessity of wading through water. It is well known that human babies can walk in shallow water before being able to walk on dry land. It is also noticeable that the only primate in the wild who regularly walks on two feet is the proboscis monkey of Borneo - a primate that is frequently constrained to walk in shallow water. One possible scenario among others is that some of our ancestors were isolated on an island when a part of East Africa was covered by the sea.

 When ancestors of the human family established bipedalism as their usual mode of locomotion, favorable conditions were met for a dramatic development of the brain. An upright posture is easily compatible with an increased head weight (we can only carry heavy weights on our heads when we are upright). Also, the coastal food chain is the best possible environment in which to find unlimited quantities of all the nutrients that are essential for brain development. Among these nutrients are the long chain omega-3 fatty acids that are abundant and preformed in seafood.10 As soon as they had access to the coastal food chain our ancestors had an ideal balance of nutrients from the land and from the sea at their disposal, and so could develop their full potential.11,12

In the 1990s a further factor has added its weight to the list of scientific data supporting the aquatic ape theory, which is our better knowledge of the specific nutritional needs of the developing brain. Until now it was impossible to explain why the human brain is four times bigger than the brain of other chimpanzees and that, in terms of the proportion of gray matter to the total brain mass, there is no difference between homo and unrelated mammals such as dolphins. One of the most mysterious aspects of human nature for modern biologists is that we have to feed an enormous brain yet our body is not very efficient at making one of the molecules ("DHA") which is essential to meet the needs of the nervous system.

Nakedness has been identified as one of the most specifically human traits since the biblical book of Genesis. It was being discussed as a scientific mystery at the time of Darwin, who rejected the notion that it was our best protection against the many skin parasites found in tropical regions, arguing that, if it was the case, other animals living in the tropics would have got rid of their hairy coats to cope with the same problem. In fact, any attempt to interpret human nakedness should start with a reminder of the main function of fur, which is to protect from variations in temperature by maintaining a layer of air around the body. In water there is no need for fur. The absence of hair is a characteristic of most sea-mammals. The only ones that keep their fur are those that can get out of the water and stay on land in a cold climate, such a seals, otters and beavers. Our subcutaneous layer of fat is as mysterious as our nakedness. It is not a feature we share with other apes although it is a point we have in common with many mammals adapted to the sea. In addition, we sweat in order to control our body temperature, and of all mammals we have the highest sweat production. Sweating has long been considered an enigma, or a mistake of nature as it depletes the body of large amounts of water and salt. This makes no sense at all to those thinkers who see humans, first and foremost, as primates who keep the characteristics of a fetus or a baby until adulthood. (In fact the human baby does not control its temperature by sweating for the first few weeks after birth). New interpretations of this sweating mechanism become possible when we consider human beings as primates who have adapted to environments where water and salt are freely available. In fact, fur seals are the only other mammals who sweat when they are overheated on land (they sweat on their naked hind flippers). Therefore sweating is yet another human trait that is compatible with adaptation to the coast.

We might focus on many other intriguing human traits such as the triangle of skin we have between our thumbs and forefingers (similar to the webbing on a duck's feet), the fact that our big toes are jointed to the others, the anatomy of our respiratory tract, or the number of blood cells per cubic millimeter. All these features suggest that we are adapted to a semi-aquatic environment.

Another feature peculiar to humans is the expression of emotion with tears. This is not incompatible with an adaptation to the sea, since marine iguanas, turtles, marine crocodiles, sea snakes, seals and sea otters weep salt tears, while land mammals have no tears or any sort of nasal salt gland. The human lachrymal glands might be interpreted as a vestige of an extra mechanism for eliminating salt. 

We might also look at one of the main obvious differences when you compare a photo of a man and a photo of a chimpanzee. One has a nose and the other only has two breathing holes. The long nose is a feature we have in common with the proboscis monkey who is a swimmer adapted to the coast. 

Another intriguing phenomenon needs interpretation and is also supportive of this new vision of homo sapiens. Consider the fact that the two wonder drugs of the last half of this century are fish oils and aspirin. It has been claimed that these can remedy an astonishing variety of conditions and, particularly specifically human diseases. Fish oil capsules have been found to reduce the risk or the effects of coronary heart disease, hyper-cholesterolemia, hypertension, psoriasis and other skin diseases, migraines, painful menstruation, different forms of rheumatism, dyslexia, attention deficit disorder, poor adaptation to darkness, allergic diseases, ulcerative colitis, Crohn's disease, pre-eclampsia, fetal growth retardation, and even some cancers. As for aspirin, it is undoubtedly the most commonly used medicinal agent in the world, and, like fish oils, can modify the metabolism of an important family of cell regulators called prostaglandins. It is as if a very large number of humans are finding they need the same sort of correction to their metabolism of prostaglandins. Theoretically, from a biochemical point of view, people who have easy access to the sea-food chain would have no need of such correction. Perhaps these modern panaceas offer us a new perspective from which to explore human nature.

This new vision of homo sapiens as an ape adapted to life on the coast represents such a radical change in the current understanding of human nature that it will take a long time to digest it. It signifies another vital aspect of the scientific revolution going on today. It is developing at the same time as the scientification of Love. It helps us to understand why human beings feel more secure in a watery environment and enables us to interpret the magic power of water on human beings.

Summary

There are similarities between the erotic power of water, the mysterious power of water on the birth process and the way in which an aquatic environment can be used to facilitate lactation. Water, as a symbol, helps humans to feel secure in a great variety of circumstances. What is the root cause of these cross-cultural effects?

References

1 Odent M. Birth under water. Lancet, 1983:1476-77.
2 Odent M. Water and Sexuality. Arkana (Penguin), 1990.
3 Leakey R, Lewin R. Origins reconsidered. Little, Brown. 1992.
4 Leakey MG, et al . New four million year old hominid species. Nature, 1995;376:565-71
5 Westenhofer M. Der Eigenweg des menschen. Mannstaede and Co. Berlin, 1942.
6 Hardy A. Was Man more aquatic in the past? New Scientist, 1060;7:642-5
7 Morgan E. The Descent of Woman. Souvenir Press, London 1972.
8 Morgan E. The Aquatic Ape. Souvenir Press, London 1982.
9 Morgan E. The Scars of Evolution. Souvenir Press, London 1990.
10 Crawford M, Marsh D. The Driving Force. Heinneman, London 1989.
11 Odent M, McMillan L, Kimmel T. Prenatal care and seafish. Eur. J. Obstet. Gynecol. 1996;68: 49-51.
12 Odent M. The Primary Human Disease: An evolutionary Perspective. ReVision, 1995;18, 2:19-21.

Excerpted and reprinted by permission of the author from Chapter 15 of The Scientification of Love.

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38 posted on 05/30/2002 9:14:22 AM PDT by Maceman
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To: Maceman
BTW, are you just opposed to the Aquatic Ape theory because you favor the kind of Savannah Ape theory espoused by Desmond Morris, or because you oppose the idea of evolution altogether? Do you prefer the creation story of Genesis?

As for Genesis, I believe it is a divinely inspired allegory for the origins of man, of which I believe evolution is an important facet.

I believe in evolution because I believe in the standard biological interpretation of the fossil evidence. As for anthropology, we have a long way to go before we've got the whole story figured out...

But we've got fossil evidence for savannah apes, and none for aquatic ones.

And it's a heck of a lot easier to make a fossil in water than on a savannah.

Further, our closest relative, the chimpanzee, is a lot closer to being a savannah ape than an aquatic one. In fact when you look at living primates, you don't find an aquatic one in the bunch.




39 posted on 05/30/2002 9:23:12 AM PDT by Sabertooth
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To: Sabertooth
Chimps aren't fully bipedal, and make tools now.

But the rudimentary and disposable tools they make aren't likely to be the kinds of artifacts that archaeologists will find in a few million years.

True, but they also aren't the kind of tools that anybody would need to carry around. You'd want to carry around either tools that were difficult to make or tools that couldn't be easily and immediately obtained. Furthermore, I would expect rude stone hammers to be employed early on in the toolmaking tradition. It's not out of the question that sophisticated organic-material toolmaking existed long before it occurred to anyone to pick up a rock to crack a nut, but it seems unlikely, in my opinion. It's somewhat surprising to me that chimps don't do this even now, and it's certainly surprising that early hominids didn't do it, but they just didn't.

40 posted on 05/30/2002 9:28:44 AM PDT by Physicist
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