Duvenoy

I myself, find the question very interesting. I would love to know the reason(s) the ancient hominids became bipedal. On the other hand, (here comes an outrageous speculation supported by no evidence what so ever) could it be that the common ancestor was bipedal and the apes later dropped to a 4 footed gate? The fossil record has yet to say and perhaps it never will. It's my understanding that great ape fossils are very scarce. Without them, piecing together the earliest history of hominids looks to be difficult at best.

doov

Vorkosigan

Things have moved on and Ergaster probably ism’t around any more, but I don’t know why he answered a question asked of Vorsigan arising from his statement: “No scientist I know of attributes all of humankind's unique features to evolution in a savannah biome. They all have much richer and more diverse views of the possibilities.”
I wanted to know more information about these “richer and more diverse views of the possibilities.”

Well, for starters, as I said, not all of humankind's unique features stem from the natural environment. Many, I would argue, arise from our unique sociality.

This thread has come up with some very interesting ideas, but those who reject the AAT as trash don’t seem to have trashed it so well that its advocates have had to change their minds.

Since AAT has been raised and rejected since it was first proposed back in the 1930s in its most primitive form, I don't hold out any hope that believers will give it up.

In any case, this may be a good thing; the orthodox view needs challenges, and once in a great while the challengers are right.

Ergaster

</strong>

I'm around. I don't spend much time on weekends on the internet (I have a family), and the AAT topic had sort of got sidetracked (although I suppose it's nice to know that some people can squeeze their nostrils shut...)

I answered the savanna question because it persists as a misunderstanding. I believe it was you who said, in response to Vorkosigan: "I am a moderately well-informed lay person who is under the strong impression that our scientific leaders are stuck like glue on the savannah scenario. If I’m wrong, then I am delighted to hear it, but why hasn’t news of these “richer and more diverse” possibilities seeped out?"

Yes, I was responding to THIS statement in order to try to emphasize the point that "our scientific leaders" (assuming by that you mean "professionals in the field" are NOT stuck on the "savannah scenario". It is a point I made several days ago. I was puzzled, therefore, given that it has already been said to be a false perception, why you repeated it as if it were true. Especially puzzled since you had referred to my post in which I said it, so I knew that it was not simply because you missed the post.

</strong>

And I asked you several pertinent questions with a bit of discussion in order to judge how much detail and in what fashion I should respond. You seem to have ignored them in their entirety. There is a VAST body of professional literature on the origin of bipedalism and related subjects, and it would be impossible to do justice to it in the absence of any notion of how much, if any, independent research you are willing to do, or how much background knowledge you possess in order to evaluate some of the claims and hypotheses. It's easy to give sound-bite responses, but how meaningful is it, really?

</strong>

Calm down. Nobody "attacked" you, and nobody implied you were *anything*. But go back and reread what you wrote. It would be quite easy to infer from your *own words* that if media accounts get garbled, then it is the fault of the scientist. You may not have intended for this inference to be made, but it certainly can be.

I asked you those questions because I know for a fact that the media has reported things that certain scientists did not say, or has completely messed up the context of a certain discovery, or has reported a discovery with the focus on controversy and not science. I am not "accusing" you of this; I am trying to determine what restrictions and requirements science reporters work under. I assume they differ for different media. I agree with you to the extent that one should try to provide accurate information to the media, so how should scientists go about it from their end?

(Just as an observation--and this IN NO WAY implies anything about you personally--many paleoanthropologists have a very jaundiced view of the popular media and the way it reports human evolution. And it's not just because of nasty dispositions on their part...)

</strong>

Well...history suggests that true advocates of *any* fringe idea will rarely change their minds. Certainly not during brief internet exchanges. The best we can do is try to emphasize that the body of evidence against AAT is far larger than any evidence for it, but exploration of the depth of that evidence is beyond the scope of a discussion board.

</strong>

This goes back to some of the questions I tried to get you to address. In one of them I was trying to make the point that "dramatic" is a subjective evaluation of YOURS, and many if not most of the experts would actually disagree with you. Perhaps it is a matter of perspective, since most evolutionary biologists are accustomed to viewing humans as a part of the continuum of nature, and not apart from it. We have satisfied ourselves that the differences between us and chimps are qualitative and not quantitative. From our perspective, the differences between humans and horses, say, are dramatic. The differences between humans and chimps are not.

Bipedalism certainly is a unique adaptation among *currently living* primates, but (again, going back to my original questions and points), there is suggestive evidence that it may not have arisen only once. That is, 6 million years ago, some sort of bipedalism may have been a rather more common adaptation among early hominids thatn we tend to think. We do know for a fact that there were a large variety of Miocene apes, and if the anatomical analysis is reliable then at least one of those apes (unrelated to humans) evolved a kind of facultative bipedal shuffling gait before our ancestors got on two feet.


</strong>

That may be true, but apparently (I need to check a source or two) bipedal wlaking is more energy-efficient than quadrupedalism.

The evidence for bipedalism precedes that of stone tools. Of course, we don't have much evidence of anything other than stone tools for early hominids, and no evidence even of stone tools from a time that might coincide with the origin of bipedalism.

The problem with scientific explanations is that, at some level, they have to be testable. It is easy to come up with all kinds of scenarios about how humans eventually became upright, but most of them suffer from the fact that they are not and can never be testable. The best of them are consistent with other evidence, such as anatomy and functional morphology, phylogeny, and taphonomy, but I fear many of them can never be anything more than interesting scenarios plausible to a more or less variable degree.

In other words, we can and do know that humans and their extinct relatives *were* bipedal, and we can examine *how* they were bipedal (i.e. the ways in which the bipedalism of our ancestors differs from our own), and we can try to establish what the precursor to bipedalism was (the evidence seems pretty strong now that the last common ancestor of humans and African great apes was a knuckle-walker, but this has long been a controversial point), and if the fossil record of hominids from the relevant time period continues to improve, we may well be able to one day establish whether bipedalism was a one-time event or occurred more than once in closely-related lineages.

Unfortunately, we will probably never be able to establish exactly *why* humans became bipedal--that is, what *exact* environmental pressures led to its adoption. There is far too much that we need to know about the past environmental and social circumstances of our ancestors that we can never recover. However, as I mentioned above, some ideas are more in line with the available evidence than others, but unfortunately AAT is not among them. For example, it is simply specious to cite "fear of water" or "ability to close nostrils" as evidence for it in the absence of any evidence whatsoever of whether our ancestors had such a fear or ability or not. Chimps are our closest *living* relatives with 6 or so million years of evolution behind them. They are not proxies or models for the LCA of chimps and humans. Most of the evidence cited for AAT is of a similar sort as those two examples. Certainly there is no *fossil* evidence which supports the scenario.

atrahasis

Could somebody please give sites with enough information on the following::[LIST][*]The possible origin of speech in Homo Sapiens[*]All arguments explaining why homo sapiens lost hair[*]All arguments explaining why the the transition from Homo erectus to Homo sapien is too sudden compared to the one from homo habilis to homo erectus:::

By so doing you will have educated one more lay person in your life and thus acomplishing one the fundemental goals of an infidel...

Let the mystery be taught by the wise to the wise

Stephen T-B

Thank you, Ergaster, for that long, considered, interesting and helpful reply.
I was taken-aback by your tone earlier on.
Journalists operate under many constraints, as I am sure you realise, and one of them is to get people to read their articles.
This usually means the journalist - or the sub who handles his copy, or the news editor who has an over-view of what’s going on - will select a highlight, and this very often has the effect of distorting the message.
I’ll give you an example: a scientist identified a virus in the saliva which might have accounted for some cot deaths. He called a press conference (or his university did) at which this finding was described. One journalist asked: “Does this mean that a mother who kisses her baby might pass on the virus to it?”
The scientist believed the chances of this happening to be extremely unlikely, but he could not absolutely rule it out, and he said as much.
You can imagine his feelings when next day he opened the paper and read that a mother’s kisses could kill her baby.
I do know that scientists and other experts grow very wary of journalists, and with good reason.
For myself, I am not a science journalist: I am an all-purpose features writer on a paper which does not give me a steer as to the line my articles should take, and I have 1,000 to 1,500 words in which to get across the subject I am writing about. It is inevitable, however, that I will sometimes give an emphasis which the person I’m interviewing hadn’t anticipated. (Mrs Jones: “Our annual bed race raised £15,000 for cancer relief and 42 teams took part.” Journalist: “Did all the teams finish the race?” Mrs Jones: “All but one.” Journalist: “What happened?” Mrs Jones: “The 80-year old team member who was helping to push the bed had a heart attack and was rushed to hospital.” I can promise you that Mrs Jones would be very disappointed by the report of her event as carried in the next day’s paper.) The fact is that journalists and those they talk to very often have a different agenda, but if I’ve interviewed a scientist then I will almost always check my article through with him or her before putting it through for publication, simply to avoid making stupid mistakes.
Thanks to your last post, I now have a much better grasp than I did have of the topic under discussion. I do think that we tend to be drawn to simplistic solutions (Creationism being the most simplistic of all) and that the appeal of AAT is / was its simplicity. I am happy to accept that the story is, in fact, enormously complex and might take a great deal of unravelling.

Amen-Moses

The current term used to describe the environment of our oldest bipedal relatives is "Mozaic", many papers that are purely interested in the bones themselves do not go very far in describing what this term means but if you sidestep slightly into different fields of Geology, e.g Paleobotany, which are much newer disciplines, you start to get a better idea of what they actually mean. The closest laymans term (that I use a lot) which really gives a decent picture is "Flooded forest" or you may see the term "wet arboreal".

Now these terms do not mean that the environment is permanently flooded (after all very few trees can cope with this) but a seasonally flooded forest which may be dry for maybe 2 months of the year and swamplike for a few months but flooded (at varying depths from year to year) for over 6 months of the year.

This describes some areas of the Congo today, areas bordering Bonobo land and the Zambeze basin (both rich in humans) but in the past described huge tracts of Eastern and North Eastern Africa all the way up to present day Yemen. These areas have two things in common: 1) they have been through several cycles of almost total inundation and virtual drought as sea levels rose and fell (as opposed for example to the reasonably steady environments of the upper Congo where the Chimp/Bonobo split seems to have occured) and 2) They are areas rich in hominid finds.

I believe strongly that these were the sort of extreme environmental pressures that drove human evolution rather than some steady change from arboreal to savannah environments.

Or to put it another way, without those sea level changes and without the Rift Valley I don't think hominids would ever have evolved.

Amen-Moses

Ergaster

Hm.

First, some clarification: I did my graduate research on the paleoecology of Olduvai Gorge and Koobi Fora. I may be uniquely qualified (here, at least), to address this particular post. At any rate, I don't often get a chance to drag out the result of two years' worth of intensive reading.

So...all I can say is...just about all of Amen-Moses' post is erroneous in one way or another.

First problem. Paleoecology is not an obscure field in human evolution. There is an enormous body of literature out there. It is common practice for the first published article on a major new fossil to be accompanied by an article on the geological and paleoecological context of the find.

Second. The term "mosaic" in hominid paleoecology does *not* mean "wet arboreal" or "flooded forest". It means pretty much what it appears to mean: that within the context of the specific find, the evidence suggests a mix of habitats within fairly close proximity of each other. This evidence is drawn from several avenues, largely the makeup and proportions of the fauna, but also including things like depositional history, paleopedology, palynology, kinds of sedimentary deposits, soil carbonates, and others.

Third. Since the geological and faunal context for the earliest fossil bipeds is easily available in the literature, it is a simple matter to actually check and see if the habitats of these hominids corresponds to what Amen-Moses says it is. The short answer is: it does not. There is zero suggestion for "flooded forests" or anything remotely resembling the Congo basin or the scenario Amen-Moses claims.

The long answer (in no particular order):

Vignaud et al. 2002. Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature 418:152-155.

This paper provides the geological context for the recently-announced hominid skull from Chad. The environment is reconstructed as being diverse: wetlands and probably a lake with some gallery forest but a considerable amount of grassland and possibly even desert in close proximity. Just out of interest, 55% of the fossil mammals are of grassland-dwelling antelopes. Note the term "mosaic" ...the TM 266 vertebrate fauna contemporary of the Toros-Menalla hominid suggests a mosaic of environments, from gallery forest at the edge of a lake area to a dominance of large savannah and grasslands. (p. 155).

Pickford M & Senut B. 2001. The geological and faunal context of Late Miocene hominid remains from Lukeino, Kenya. C.R. Acad. Sci. Paris, Sciences de la Terre et des planetes 332:145-152.

This article accompanied the announcement of the 6-million-year-old Orrorin tugenensis hominid last year from Kenya. The environment is reconstructed as an alkaline lake with nearby dense woodland or forest, but a predominance of open woodland. The dominant fossil mammal is an ancestral impala.

Woldegabriel et al. 2001. Geology and paleontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia. Nature 412:175-178.

This paper accompanied the announcement of Ardipithecus ramidus kadabba last year. Since fossils came from two different localities, there are actually two somewhat differing habitats sampled. One is predominantly moist forest or dense woodland (not "flooded" by any means) with nearby grasslands, and the other is more open, grassy woodland. This is a similar environment to that of the original Ar. ramidus discovery.

These three articles describe the paleoenvironments of the oldest currently-known hominids which are claimed to have been or probably were bipedal. Forest and woodland are common components of these habitats, but in all of them the predominant fauna are rather more open and dry-adapted antelopes. There is no evidence of very wet forest, or of seasonal flooding of several months' duration, or really of any sort of flooding at all (I suppose it need not be mentioned that virtually *all* fossils are preserved in aquatic environments simply because those are depositional environments. Terrestrial environments tend to be erosional and thus do not preserve fossils, with rare exceptions). Therefore, there seems to be no evidence in the literature for the kind of wet or water-logged habitat that Amen-Moses proposes.

Further investigation of the literature shows that as hominids get younger (i.e. as we move into australopithecine times), the habitats tend to get drier. Of course, by that time, hominids were firmly-established bipeds.

Four. Amen-Moses seems to be proposing that the Rift Valley somehow was repeatedly inundated by rising sea levels. There is absolutely no evidence in the geological record of the rift valley(s) that this ever occurred. He is correct in that the rift valley(s) are the focus of the majority of hominid sites, but they are also the focus of virtually all *hominoid* and other fossil primate sites as well, going well back through the Miocene into the latest Oligocene (about 30 million years ago). In other words, the geological and environmental contexts of the rift valley(s)sites have been studied for a long time, now. The trend, if there is one, has been towards increasing aridity, and not cycles of flooding.

Speaking from my own research (and the references are too numerous to mention), there certainly is no evidence of any such occurrances at Olduvai Gorge or the Turkana Basin (Omo, Koobi Fora, and West Turkana localities), although admittedly those are late Pliocene/Pleistocene in age.

For an overview of the field of paleoecology and ancient ecosystems, try:

Behrensmeyer et al. 1992. Terrestrial Ecosystems Through Time: Evolutionary Paleoecology of Terrestrial Plants and Animals. Chicago: University of Chicago Press.

For a specific look at the African hominid and hominoid paleoenvironments, and whether there is any evidence for Amen-Moses' claim, try:

Andrews P and Humphrey L. 1999. African Miocene environments and the transition to early hominines. In T. Bromage and F. Schrenk (eds.): African Biogeography, Climate Change, & Hominid Evolution. New York: Oxford University Press, pp. 282-300.

Partridge et al. 1995. The influence of global climatic change and regional uplift on large-mammalian evolution in East and Southern Africa. In Vrba, Denton, Partridge and Burckle (eds.): Paleoclimate and Evolution with Emphasis in Human Origins. New Haven: Yale University Press, pp. 331-355.

Pickford M. 1990. Uplift of the roof of Africa and its bearing on the evolution of mankind. Human Evolution 3(1):1-20.

There are many other references, of course.


[ September 16, 2002: Message edited by: Ergaster ]</p>

Peez

First, I would not call south sea islanders "semi-aquatic", but that is a semantic argument. Second, the latter comment is unsupported. In our culture ("Western") we tend to cook nearly everything, including sea food, but even now the great majority of things that we eat raw are not sea food: fruit, many vegetables, and most dairy products. In any event our eating habits have evolved culterally and it is perhaps dangerous to draw too many conclusions from them. Do you have a reference for this? My ancestors lived on an island, but I cannot close my nostrils (nor can, as far as I know, anybody that I know). Reference? Note that close relatives of the elephant have been known to have thick fur. This suggests that there has been enough time to evolve a fur coat since the most recent common ancestor of elephants evolved. Why haven't elephants evolved such a coat? Perhaps the same could be said of other mammals. This sounds like another "just so story". We know that humans with stone age technology survived quite nicely on the savanah. Naturally you are entitled to your opinion, as are creationists. I am not saying that the AAT is on the same footing, but neither is it seriously considered by scientists.

Peez

[ September 17, 2002: Message edited by: Peez ]</p>

Peez

That is a semantic question, but in any event it would be strange to define them as "semi-aquatic" merely because they eat seals (I would not consider the osprey or grizzly bear "semi-aquatic", but they eat fish. Are you defining "semi-aquatic" as anything that eats fish? I am not sure about what you mean by "long distances, but you seem to be basing your evaluation of the AAT on rather vague notions of what constitutes a semi-aquatic animal, and some assumptions about how good certain animals are at swimming. Of course not, they are all closely-related. Like many other semi-aquatic animals they have relatively short limbs, especially hind limbs. They are quadrapeds on land, have a thick, rich pelt, very small external ears, and a terminal nose entirely unlike ours. Reference please. I have yet to see anyone close their nostrils. I have yet to see anyone of any ancestry who can close their nostrils (I live in an area where people who have descended from the areas mentioned are relatively rare). Some dive, many do not. The fact that humans dive does not in any way suggest that we had a recent semi-aquatic ancestor.

Peez

Peez

This implies that you know something about the swimming abilities of quite a few animals. After all, your comment is meaningless unless you know something about this area. Could you please provide references for your position that few mammals could "swim 21 miles in extremely cold and rough seas". How effecient do you think that we are, relative to an otter (for example)? Where did you get this information? On what do you base this assertion? You seem to be just imagining that sea otters might be this way, then stretching that into an assertion that they are that way. I fail to see your point here. It would not be surprising if bears that lived in an area where there are opportunities to swim might be better swimmers than those who do not. That does not make the bears that live in an area with at least some water "semi-aquatic" by any definition that would not also include wolves, coyotes, foxes, cougars, lynxes, bobcats, deer, moose, elk, porcupines, white-footed mice, snowshoe hare, etc.

Peez