A New Twist on the Aquatic Ape Theory

[gwolf]

Largenton, to make sure I really understand you, are you saying that regardless of species or regardless of previous physiology, increasing one's intake of fish DHA always increases cranial capacity? If this is so, perhaps it explains the increasing cranial capacity of hominids with a fishy diet. If not, why is it relevant?

Also, are you further claiming that only fish and not mollusks or crustaceans are a source of this protein?

George Wolf

[gwolf]

First, let me apologize for not giving a more complete account of the freezing water rescues I've read about. In fact in the accounts I've read about from North America, upon rescue, a tracheotomy is performed to aid breathing, and until the patient is stabilized in some other ways, a coma is usually induced.

Muchy, thank you for all that information on the Mammalian Dive Reflex (MDR), which certainly adds some perspective to all of this. At first I thought a falsifiable test had been discovered, but on reflection I'm not so sure.

It is stated by Muchy that the MDR is weaker in humans than in ceteceans and other oceanic mammals. I will now posit that this is exactly the right thing for an amphibious hominid while in lake water that is close to skin temperature. Our immersed hominid functions at full capacity on the surface or in dives not exceeding standing height. However, on deeper dives, the reflex does what it is supposed to do. I don't know the temperatures at depth in the rift lakes, but I'm quite familiar with diving in temperate mountain lakes after two months of summer. As you may know, cold water is denser than warm water, and so always sinks to the bottom. Thus the deeper you dive, the greater the difference between water temperature and body temperature. At depth in a temperate mountain lake, the water is noticeably colder. If this is also true of the Rift Lakes, the deeper our hominid dove, the greater the chance that the full dive reflex would be triggered.

You have again said what somebody else said, which is that "human skin is not fit for staying in water a long time." I don't envision our hominid remaining immersed for more than about two hours at a time. I don't know about you, but I've been immersed that long and survived quite well, other than my fingertips and toe tips becoming wrinkled. As I've said before, I envision a particular type of amphibious existence, for which I think some evidence exists. I certainly don't mean a fully aquatic hominid in the sense that a cetecean is aquatic.

Finally, I think that by "kajak" you actually mean the word spelled kayak in English; the enclosed one-man seal skin boat used by the Inuit and Ainu.

Thanks for your response,

George Wolf

[gwolf]

Oh, one more thing:

Then there is the "escape the cat"-idea. Big cats are not necessarly afraid of water nor is this an intrinsic feature. Look at tigers, some races of domesticated cats, smaller african cats and so on. The fact that lions tend to stay out of the water can not be extrapolated to every species of cat.

A band of hominids would fear lions most of all, as they would be the hardest for them to fend off. As a group, they'd at least have a chance against the smaller (swimming) cats, who would be at more of a disadvantage in water over their heads than would a swimming, diving hominid. In addition, the cat would fear crocodiles, and possibly not know that the hominids had killed them off.

George Wolf

[DavidMcC]

Largenton, if fish consumption lead inevitably to brain development, that we woud have to abandon Darwinian evolution, which insists that natural selection has something to do with it. I thought that fish consumtion was useful to enable brain development, but wasn't sufficient to ensure it, otherwise, even pelicans would be geniuses!

[Muchy]

[...]
You have again said what somebody else said, which is that "human skin is not fit for staying in water a long time." I don't envision our hominid remaining immersed for more than about two hours at a time. I don't know about you, but I've been immersed that long and survived quite well, other than my fingertips and toe tips becoming wrinkled. As I've said before, I envision a particular type of amphibious existence, for which I think some evidence exists. I certainly don't mean a fully aquatic hominid in the sense that a cetecean is aquatic.

I've read the thread, but I'm not very convinced. All the adaptions you mentioned seem to be either existant in the whole mammalian kingdom or do not in particular point to aquatic lifestyle. In addition, we and in fact all apes and monkeys alike lack a lot of features commonly found in semi-aquatic animals (I'm thinking of beavers, otters, ..) or fully aquatic sea-animals (whales, dolphins, ..) and have some which are disadvantages in water. I do not doubt that some of our ancestors may have lived along shorelines and, as I would expect them to do, integrated that into their behaviour and life, but given that we are ill-adapted to water I can not envision a large benefit from living in an environment so dangerous as water (drowning, hypothermia, easy prey due to low speed, density-difference between eye and surrounding water, thus poor vision, open ears and nostrils)

Finally, I think that by "kajak" you actually mean the word spelled kayak in English; the enclosed one-man seal skin boat used by the Inuit and Ainu.

Yes, in principle, but I had a softer definition in mind, as for me any long, thin boat with a single "seat" is a "kajak", for example those here

It's rather hard, especially on more complicated topics, to think in german and, at the same time, type in english. I'm sorry and apologize for that mistake.

M.

[DavidMcC]

Muchy, I agree we don't see well in water, but are our noses not the only ape noses that can be partially constricted (slowing down water penetration, especially with the mouth shut), even though they didn't get to complete the process. Perhaps the water got too cold before this, like other adaptations, could get any further.
I have noticed that some arguments against (semi-)aquaticism rely on the imperfection of it, missing the point that no-one claimed it had time to go to any kind of completion, or that strong ties to the land constrained it in any case.

[DavidMcC]

One aspect that hasn't been considered here (or anywhere else to my knowledge) is how much phenotypic plasticity we may (or may not) have with respect to an aquatic lifestyle. I know that human babies are much more confident in water (even love it!) if they have been introduced to it in the first few months of their lives, but I don't know what happens if many generations spend a lot of time in water, nor do I know how the babies of other non-aquatic mammals behave if introduced early to water - would they like it as much as human children?

Most phenotypic changes due to plasticity would quickly revert once the diet and/or lifestyle went back to a non-aquatic one, making it hard to get good evidence without doing possibly socially unacceptable experiments!

[Muchy]

Muchy, I agree we don't see well in water, but are our noses not the only ape noses that can be partially constricted (slowing down water penetration, especially with the mouth shut), even though they didn't get to complete the process. Perhaps the water got too cold before this, like other adaptations, could get any further.
I have noticed that some arguments against (semi-)aquaticism rely on the imperfection of it, missing the point that no-one claimed it had time to go to any kind of completion, or that strong ties to the land constrained it in any case.

I will try to inquire that. I honestly don't know. The modern human nose is not able to close, even if I apply external pulling force (as muscles can only pull). If the nasal cartilage would be less stiff one could maybe close the nose with a well trained m. nasalis. Anyways, that is speculation. I'll see if I can find anything in my books.

Concerning your second statement, I am well aware of that. While typing my last response, I thought about adding that it of course could be that some features have not fully developed or, once out of the water finally, were so heavily selected against they dissapeared quickly. I then decided I will try to include only things which I think are very basic and can not evolve quickly and in need and dissapear again within reasonable time, as the timeframe discussed here is rather small.

M.

[gwolf]

Muchy, again I repeat my mantra from an earlier reply. It isn't sufficient to say that hominids lack certain features of other mammals that are either aquatic or amphibious. Please continue to enumerate them to see if we can find a falsifiable test. So far we haven't, and I personally lack confidence in any of theories that show h.sapiens as fully terrestrial with only terrestrial ancestors.

Mr. McCall has pointed out that the evidence points to h.sapiens being a generalized or transitional creature rather than a highly specialized one, as any cetecean would be. I think the recent arrival of hominids in the fossil record, and genetic tests comparing human DNA with that of other apes seems to bear this out. Perhaps more dramatic evidence of this is the demonstrated current adaptability of the species to just about every terrestrial environment on the planet from torrid to arctic. It seems to happen despite such local adaptations as skin color.

I want to stir the pot a little bit more with h. sapiens' sexually dimorphic hair patterns. Does any other ape exhibit this? If not, this looks to me like another adaptation for an amphibious existence. Competition swimmers often shave their bodies to reduce water drag, including their heads. Male pattern baldness looks like a natural "shave." Young males have a full head of hair, it appears just long enough to attract a mate. Females retain a full head of hair, but have hair growth suppressed more than males over the rest of their bodies. As I further understand, there are people in Africa with a lot more suppressed hair growth in both sexes. If this is the case, I propose that this advances the theory of the amphibious ape (the most appropriate term now) as follows. North Africans, Europeans and Middle Easterners being descendants of older evictees from the rift lakes, would naturally have been less adapted to lake life and therefore be more hirsute. This only partially explains people in the Orient, one group of which has more hair than the other. However, in Japan at least the less hairy people are known to be more recent arrivals than the Ainu, who have more hair. Further, both groups are said to be hairier than other oriental peoples.

I'm still having fun with this.

George Wolf

[JeffLee]

Where did he first use the term?

http://paleobiol.geoscienceworld.org/cg ... ract/8/1/4

fricken spell check keeps messing /e x a p t i o n/ into exadaption. >.>

I think the amphibious migrating lake dweller makes the most sense. Austrolopithecus would have used stones to open bivalve mollusks. Being too small or not smart enough to challenge the crocs, it would have started with smaller water holes. It would have escaped the big cats in the water and big crocs in the trees. Its bipedalism would both have helped fishing and migrating. I didn't say it in my initial "fantasy," but there are still people in the tropics who fish while immersed to their necks.

the thing is, you say it's convincing, but i can't see things your way. you apparently know something i don't because i haven't seen much of anything in the way of evidence.

the thing is, AAH seems to have things going both ways (IMO). they want sexual selection to go for the thinner ape, why? did the females find members of their species suffering from pneumonia to be particularly attractive? [surely you don't suggest the waters where 37C ^^]

it has apes going to water for food but does not show any significant gains in DHA until late erectus, despite the apparent enablement of growth via the fish heavy food supply and the pressures that were being exerted towards a bigger badder brain. [before the growth spurt in largeys data brains were still being selected for as evidenced by tools and the fossil record].

it also has apes going to water to "escape" predators but does not show any morphological traits suggesting that they were adapting themselves towards the standard swimming styles that would have both increased their food supply and provided protection from freshwater sharks and gaters. all to escape a fruit laden terrestrial landscape that still had enough forest cover to protect the apes from the odd predatory cat, cats that, assuming they were rather chimpanzee like, probably avoided them. [large cats can and do eat large apes like chimps but it is a rarity- to the point where it can and in some instances has been, ascribed to the actions of 'risk taking' individuals rather then a species hunting species situation where they are sympatric.]
http://cat.inist.fr/?aModele=afficheN&cpsidt=4499883

Easy to kill a croc? that's an opinion i am not inclined to share. ^^ BTW can you tell me the page/chapter of that new guinea hunter/gatherer claim in 'guns germs and steel', I'd like to read that.

It appears then that the fossil evidence favors nobody in this. We know that monkeys avoid being mired in mud the way large animals like hippos could, so this makes it more likely that the fossils are found where hominids died or were taken as prey.

that's what I'm saying, that line of evidence favours no one in this issue. [well technically it favours me because i never entered it as evidence, but lets not interrupt my evil behind the scenes laughter].

Are you willing to prove to me that the same fish intake that is supposed to be "healthy" for humans is likewise "healthy" for chimpanzees?

What? three things:

- as far as i know the health effects of eating specific food simply isn't studied in chimps.
- wouldn't that be shooting myself in the foot anyway? if i prove it is then you have a line for the CA to jump into the waters, if the humans have an advantage now you have selection. >.>
- I was talking about tolerance for red meats anyway, since we both eat those and we know we do it better. [which suggests to me that our diet was richer in red meats throughout our evolution].

Ah, but the waters I'm talking about are close to skin temperature already, so the loss of fur won't neccessarily mean a cold Australopithecus. On the other hand, if subcutaneous fat does come along, that opens up a few more lakes for settlement, or makes it easier to explore deeper water.

"The data sets will be used to drive numerical simulations designed to explore the impact of climate forcing mechanisms and feedbacks during the middle Pliocene. Estimates of middle Pliocene global warming suggest that temperatures were approximately 2 degrees C greater than today."
http://directory.ei.columbia.edu/displa ... jectid=547

what lakes do you know [outside of Iceland or volcanism] that can get close to 37C? do we have evidence of these lakes being heated by some means?

As previously mentioned, climb the trees to avoid the crocs and dive in the water to avoid the cats. The trees would make it easier to spot crocs in a new lake, or maybe even let them live with the crocs -- assuming you had good lookouts and only entered the water when you could see the crocs as they swam.

Why bother with the water? two birds one stone [or in this case, tree].
Parsimony.

I can't comment on objections to the hypothesis that I haven't seen!

It's up there somewhere, in his first post i believe.

We don't have to talk about arid environments, then. I think the invention of the ancient equivalent of the canteen (a gourd most likely) would still be needed to pursue prey as relentlessly as as you suggest.

why? wolves don't need them, they pant we sweat. they got the short end of that bargain.

is better adapted than one afraid of water (as some primates are).

a trait many humans share with primates.

I'm saying that all along, some hominids got evicted. Some of them happened to find other environments where they thrived.

all along what?

geh, i need structure. ^^ dates, locations, lakes, local geology, radiation, paths of least resistance, chains of lakes going to Asia and Europe for erectus sites or a 'point' where you think erectus left the water [animal bones and erectus tools like to hang around each other, and their is a distinct lessening of sexual dimoprhism suggesting a co-operative social structure]. was habilis a precursour to the landbound hunters? I want predictions and testable results. I crave it... my precious... the fat hobbits knows! err. ignore that last bit. >.> [damn hobbiteses, I'm looking at you LB1].

I'd read all the rest of the posts but... honestly, just got home and i don't give a fudge right now. ^^

[Muchy]

Muchy, again I repeat my mantra from an earlier reply. It isn't sufficient to say that hominids lack certain features of other mammals that are either aquatic or amphibious. Please continue to enumerate them to see if we can find a falsifiable test. So far we haven't, and I personally lack confidence in any of theories that show h.sapiens as fully terrestrial with only terrestrial ancestors.

That's great. Being inquisitive is a very good fuel for science. Yet I think that I will now present a slightly different mantra, which is
"You present a hypothesis. You prove it."
As far as I know, the aquatic ape theory is not widely supported. Therefor the basis on which we have to base our exploration is that homo sapiens has not been semi-aquatic and it's ancestors neither; it's therefor up to you to provide facts which can be considered evidence for a diverging theory. So far I am not convinced, and that is my crucial point, of your hypothesis because those things mentioned can either be found in other mammals which are not aquatic and I suppose that's not due to convergent evolution but common ancestors and because they often are not an aquatic feature.

Concerning the insufficiency(???) of pointing out that other semi-aquatic animals have features we have not: I give you that, yes. We could have come up with something new. Yet I still think it's valid to ask questions. If we had been on our way to a semi-aquatic life, we should see some basic evidence, like closeable eyes and ears or adaptions of the eye and ear to cope with dense water for instance. Maybe you could list what you consider evidence (in a bulleted list), maybe I've overlooked it too eagerly. Additionally, it is insufficient to point out which feature we (at least it seems so) share with aquatic animals.

Mr. McCall has pointed out that the evidence points to h.sapiens being a generalized or transitional creature rather than a highly specialized one, as any cetecean would be.

Hm. One might think we are highly specialiced. We are highly specialiced, social prediction machines. That may be human specialization. Other animals can do almost everything better. Most land animals ranging from 30 to 270cm (about 1 to 9 feet) are faster than we are. Most land animals have better or more specialized orientation and recognition organs. And so on. Yet no animal we know has the cognitive features we have. We're specialized in survival by thinking and adapting based on our observations.

Well your next paragraph is a good ending to my paragraph, too, so I'll leave it as it is.

I think the recent arrival of hominids in the fossil record, and genetic tests comparing human DNA with that of other apes seems to bear this out. Perhaps more dramatic evidence of this is the demonstrated current adaptability of the species to just about every terrestrial environment on the planet from torrid to arctic. It seems to happen despite such local adaptations as skin color.

and then hairlessness

I want to stir the pot a little bit more with h. sapiens' sexually dimorphic hair patterns. Does any other ape exhibit this? If not, this looks to me like another adaptation for an amphibious existence. Competition swimmers often shave their bodies to reduce water drag, including their heads. Male pattern baldness looks like a natural "shave." Young males have a full head of hair, it appears just long enough to attract a mate. Females retain a full head of hair, but have hair growth suppressed more than males over the rest of their bodies.

I'll adress the swimmer-point later in this posting.

Male baldness is a sign of your body aging and is due to high testosterone levels iirc. The same process that ultimately makes man bald is partly responsible for prostate cancer. Female humans actually have the same problem, but lower levels of testosterone keep them from becoming fully bald. And, by the way, old men tend to become hairy everywhere else. I do not know if a massive beard, lot's of body hair or ear hair is a good indicator of aquatic life. Our early ancestors did, to further my point, probably never reach an age sufficient for serious hair loss, anyway.

And then there is the really crucial point: Hairlessness is not a distinct aquatic feature. If you look at mammals, you quickly notice that bigger animals tend to be hairless, smaller not. Otters, beavers, muskrats and platypoda are not hairless.
Seals and sealions show some hair. As we go on to finally reach whales, which are arguably bigger, there is nearly no hair left.

Of course whales have very specialised skin. Porpoises show skin patterns resembling sharks. Orcas also have specialized skin. All fully-aquatic hairless animals have skin of a different type (and even seals show that particular adaption) which has a different top layer and does not get soaked with water.

So which mammals are hairless? Extremly large (elephants, rhinos), extremly fast-swimming, those naked moles and us.

Why is that? Large mammals have a severe problem with thermoregulation. The bigger you are, the lower the volume/surface-ratio, thus less heat dissolves. Being hairy adds to that problem. Moles live underground. Being a fast swimmer hair can be a problem. But totally smooth skin is not good either, which is why modern swim suits are rigid and show a flakey pattern.

As I further understand, there are people in Africa with a lot more suppressed hair growth in both sexes. If this is the case, I propose that this advances the theory of the amphibious ape (the most appropriate term now) as follows. North Africans, Europeans and Middle Easterners being descendants of older evictees from the rift lakes, would naturally have been less adapted to lake life and therefore be more hirsute. This only partially explains people in the Orient, one group of which has more hair than the other. However, in Japan at least the less hairy people are known to be more recent arrivals than the Ainu, who have more hair. Further, both groups are said to be hairier than other oriental peoples.

So Africans are more amphibious and thus have less hair. Orientals which live in northeast africa and asia on approximately the same latitude as africans are not, which is only partially explained by your hypothesis. People in europe and northern asia are rather hairy allthough there are arguably more rivers and seas in moderate climates, yet the northernmost humans, the inuit, which presumably left first, do not show much body hair, and that is not because the are semi-aquatic (unless they have lot's of blubber to not immediately freeze, of which I'm not aware of)

How those that even partially fit? We should probably look at how which group of humans got where they are now before we discuss that.

Now back to the main point, fast swimming.

A study made in the seventies shows that shaving may reduce drag and increase the swimming speed of humans by about 3-4%. An olympic swimmer clocks in at about 6 miles per hour. Any predator hunting swimming humans, shaven or not, will have them for lunch. So does it make us faster? Probably, but not fast enough. Additionally, the best surface pattern for swimming seems to be rather rigid; look at the skin of fast swimming animals like sharks or some whales. There also is a book with the title "Animal skin" or "Mammal skin", I can not remember exactly, which discusses an experiment that shows that bare skin in sealions is worse in reducing drag then the particular fur they have. And how should hairlessness be a selection criteria if early homids did not swim a lot? While wading hair won't matter. It's the upright position that makes wading extremly exhausting and slow, not body hair. And why is there so much hair on our heads? Why is it that we can not swim well, but show high dexterity on land? Hairlessness seems to be an advantage and a disadvantage if you look at it closely. And it is a disadvantage in water if you happen to be blubberless.

I'm still having fun with this.

After typing all that I found a page dealing with some of your points. I will not change my posting as I think it is not honest to do so, but I will add the book is called "Mammal skin". You can look for yourself.

[url="http://www.aquaticape.org/hair.html"]Aquatic Ape/Hair[/url]

M.

[gwolf]

the thing is, you say it's convincing, but i can't see things your way. you apparently know something i don't because i haven't seen much of anything in the way of evidence.

the thing is, AAH seems to have things going both ways (IMO). they want sexual selection to go for the thinner ape, why? did the females find members of their species suffering from pneumonia to be particularly attractive? [surely you don't suggest the waters where 37C ^^]

Wherever did you get THAT idea? "Skin temperature" (approx 23C) is not the same as "body temperature," except around the anus and sometimes the auxilia.

You have provided me with another possible argument in favor of the amphibious ape. I note that in humans the anus is deep between the buttocks, unlike the other primates, where it sits closer to the outside world adjacent to the ischial callouses. Why would it be so far retracted, especially since this makes fecal soiling much more of a problem for humans than for other mammals? I will speculate that the buttocks insulate the anus when the body is immersed, thus making it easier to maintain rectal temperature properly.

it has apes going to water for food but does not show any significant gains in DHA until late erectus, despite the apparent enablement of growth via the fish heavy food supply and the pressures that were being exerted towards a bigger badder brain. [before the growth spurt in largeys data brains were still being selected for as evidenced by tools and the fossil record].

Does this mean you are certain that DHA automatically enlarges the brain?

it also has apes going to water to "escape" predators but does not show any morphological traits suggesting that they were adapting themselves towards the standard swimming styles that would have both increased their food supply and provided protection from freshwater sharks and gaters. all to escape a fruit laden terrestrial landscape that still had enough forest cover to protect the apes from the odd predatory cat, cats that, assuming they were rather chimpanzee like, probably avoided them. [large cats can and do eat large apes like chimps but it is a rarity- to the point where it can and in some instances has been, ascribed to the actions of 'risk taking' individuals rather then a species hunting species situation where they are sympatric.]
http://cat.inist.fr/?aModele=afficheN&cpsidt=4499883

As a result of these exchanges, I suggest water as a place to flee only from lions, which is not an insignificant problem. When I checked references on freshwater sharks I discovered nothing claiming that they have ever inhabited the Great Rift Valley in Africa. So they weren't a problem.

Easy to kill a croc? that's an opinion i am not inclined to share. ^^ BTW can you tell me the page/chapter of that new guinea hunter/gatherer claim in 'guns germs and steel', I'd like to read that.

I've already dealt with that. Incidentally, crocodiles are not the only reptiles that can be killed so easily and dramatically. I've seen dramatic footage of a Bushman seizing a poisonous snake by the tail and giving it a sharp, thrashing shake. The thing immediately went limp, it's lightly built skull fractured and neck broken. I'm looking through my copy of Jared Diamond's book, but since I didn't annotate it, I think it will take awhile to find.

[That the fossil record favors nobody is] what I'm saying, that line of evidence favours no one in this issue. [well technically it favours me because i never entered it as evidence, but lets not interrupt my evil behind the scenes laughter].

It does? Each of the exchanges between terrestrial and amphibious ape advocates has been a trade-off. To test the hairy aquatic ape problems, we'd need to dress somebody up in a hair suit and have them swim off against somebody without one. The limits to the diving reflex don't mean much in rift lake waters. The problems with human skin not "designed" for immersion are moot if the hominid doesn't remain immersed for more than two hours. The problems with insulating fat distribution mean little if the water is close to skin temperature. Salinity varies from lake to lake, so the amphibious ape theory stands as long our ape avoids the most saline or "soda-y" lakes.

Are you willing to prove to me that the same fish intake that is supposed to be "healthy" for humans is likewise "healthy" for chimpanzees?

What? three things:

- as far as i know the health effects of eating specific food simply isn't studied in chimps.
- wouldn't that be shooting myself in the foot anyway? if i prove it is then you have a line for the CA to jump into the waters, if the humans have an advantage now you have selection. >.>
- I was talking about tolerance for red meats anyway, since we both eat those and we know we do it better. [which suggests to me that our diet was richer in red meats throughout our evolution].

From what I've heard and read of the years, we may indeed digest meat in general better than the pongids but digestion of meats is most efficient with fish.

Ah, but the waters I'm talking about are close to skin temperature already, so the loss of fur won't neccessarily mean a cold Australopithecus. On the other hand, if subcutaneous fat does come along, that opens up a few more lakes for settlement, or makes it easier to explore deeper water.

"The data sets will be used to drive numerical simulations designed to explore the impact of climate forcing mechanisms and feedbacks during the middle Pliocene. Estimates of middle Pliocene global warming suggest that temperatures were approximately 2 degrees C greater than today."
http://directory.ei.columbia.edu/displa ... jectid=547

This data seems to make it easier rather than harder for hominids to become lake-amphibious.

what lakes do you know [outside of Iceland or volcanism] that can get close to 37C? do we have evidence of these lakes being heated by some means?

Moot question. See my response further back.

As previously mentioned, climb the trees to avoid the crocs and dive in the water to avoid the cats. The trees would make it easier to spot crocs in a new lake, or maybe even let them live with the crocs -- assuming you had good lookouts and only entered the water when you could see the crocs as they swam.

Why bother with the water? two birds one stone [or in this case, tree].
Parsimony.

I already talked about the lions, although this may not be necessary to prove the amphibious ape hypothesis. Merely feeding on mollusks and later fish would do it.

We don't have to talk about arid environments, then. I think the invention of the ancient equivalent of the canteen (a gourd most likely) would still be needed to pursue prey as relentlessly as as you suggest.

why? wolves don't need them, they pant we sweat. they got the short end of that bargain.

We need water because we sweat, not in spite of it. Plus, hominids are bigger than wolves, exponentially multiplying their heat disposal problems.

is better adapted than one afraid of water (as some primates are).

a trait many humans share with primates.

I suggest that this is a problem induced by not being raised around water. As previously pointed out, even juvenile pinipeds won't swim until they get a forceful maternal dunking.

I'm saying that all along, some hominids got evicted. Some of them happened to find other environments where they thrived.

all along what?

geh, i need structure. ^^ dates, locations, lakes, local geology, radiation, paths of least resistance, chains of lakes going to Asia and Europe for erectus sites or a 'point' where you think erectus left the water [animal bones and erectus tools like to hang around each other, and their is a distinct lessening of sexual dimoprhism suggesting a co-operative social structure]. was habilis a precursour to the landbound hunters? I want predictions and testable results. I crave it... my precious... the fat hobbits knows! err. ignore that last bit. >.> [damn hobbiteses, I'm looking at you LB1].

I'm also interested getting falsifiable data. Would you provide me with a research grant to help me pursue this? I can't help you with the hobbits unfortunately. Where do they fit in between h. habilis and h. sapiens?

I'd read all the rest of the posts but... honestly, just got home and i don't give a fudge right now. ^^

I know the feeling. I'm having trouble keeping my eyes open.

George Wolf

[hecate]

Catching fish does not require a big brain. Lots of animals with smaller brains manage quite well. To be effective hunters however, especially for humans who have no resources such as great speed, claws or teeth we do need to be smart and have a big brain. Our brain consumes about 20% of our total energy supply even when we don't use it.

As the big forests in Africa gave way to savannas, meat (which has much greater nutritional value than plants) became available in great quantities. Humans had to be smart to be able to organize a hunt, divide food among non hunting members etc. And without the benefits other predators have, we just had to use our brains.

Now I find this a much more likely scenario than a swimming ape.

[DavidMcC]

A study made in the seventies shows that shaving may reduce drag and increase the swimming speed of humans by about 3-4%.

Muchy, as I mentioned in an earlier thread on the AAH, that low figure bears out the point that humans are more or less as hairless as necessary for efficient swimming, which would have helped for getting food in water. A more interesting experiment would be to measure the effect of shaving a chimp (as the nearest thing to the common ancestor) on his/her swimming efficiency! Of course, this might be difficult to carry out(!), but is more relevant to an alternative explanation to why we might have become hairless originally (ie, alternative to the cooling hypothesis of the savanna theory).

[DavidMcC]

Catching fish does not require a big brain. Lots of animals with smaller brains manage quite well. To be effective hunters however, especially for humans who have no resources such as great speed, claws or teeth we do need to be smart and have a big brain. Our brain consumes about 20% of our total energy supply even when we don't use it.

As the big forests in Africa gave way to savannas, meat (which has much greater nutritional value than plants) became available in great quantities. Humans had to be smart to be able to organize a hunt, divide food among non hunting members etc. And without the benefits other predators have, we just had to use our brains.

Now I find this a much more likely scenario than a swimming ape.

Hecate, I totally agree. However, the hypothesised semi-aquatic period (starting >6MYa) was well before the savanna period (~1.7MYa, from melanocortin MC1 dating - see old thread). The real question is not what gave us big brains (conclusively shown to be the savanna period), but what made us hairless and bipedal, and a separate species from chimps. In other words, what created the hominins from a hominid? That is a different speciation event altogether, as far as I am concerned.

[DavidMcC]

I think a problem in many of these detailed discussions on specific features is that animals' features/organs usually have multiple functions, and therefore their adaptation to changed circumstances is more complex than may at first appear, due to the multiple trade-offs involved. Hair is a good example. Head hair has at least two functions in humans: protection against UV (the skin on the head is particularly vulnerable to the damage which may cause anencephalic babies) and possibly to allow a plump, floating baby to hang on to mother in water, assuming that the tendency for that hair to pull out easily in modern women is a post aquatic change.
Also, comparisons with completely different mammals can be misleading. For example, the hair on an otter is highly water repellant and traps air bubbles, which reduces drag in water. Human hair does not - leaving the bare skin as the better surface to minimise drag. (Whether some fast predators can still catch us is irrelevant if the point is to get food without exhaustion, for example.)
Edit: I deleted the issue of thermal insulation of the head, because that was probably irrelevant at 6MYa.

[hecate]

Catching fish does not require a big brain. Lots of animals with smaller brains manage quite well. To be effective hunters however, especially for humans who have no resources such as great speed, claws or teeth we do need to be smart and have a big brain. Our brain consumes about 20% of our total energy supply even when we don't use it.

As the big forests in Africa gave way to savannas, meat (which has much greater nutritional value than plants) became available in great quantities. Humans had to be smart to be able to organize a hunt, divide food among non hunting members etc. And without the benefits other predators have, we just had to use our brains.

Now I find this a much more likely scenario than a swimming ape.

Hecate, I totally agree. However, the hypothesised semi-aquatic period (starting >6MYa) was well before the savanna period (~1.7MYa, from melanocortin MC1 dating - see old thread). The real question is not what gave us big brains (conclusively shown to be the savanna period), but what made us hairless and bipedal, and a separate species from chimps. In other words, what created the hominins from a hominid? That is a different speciation event altogether, as far as I am concerned.

I thought Hominines was one of the mammal groups that adapted to the open grasslands as soon as this biome appeared, about 8 Mya, and their fossils are relatively well known. The earliest to my knowledge are Sahelanthropus tchadensis (7–6 MYA) and Orrorin tugenensis (6 MYA). You want to go further back up in time ?

[DavidMcC]

Hecate, it isn't a question of how far back, more a question of whether it is sufficient to characterise the changes occurring to the African terrain from 6-7MYa simply as simply the appearance of open grassland, given the high sea levels and high temperatures around that time.

[Largenton]

it has apes going to water for food but does not show any significant gains in DHA until late erectus, despite the apparent enablement of growth via the fish heavy food supply and the pressures that were being exerted towards a bigger badder brain. [before the growth spurt in largeys data brains were still being selected for as evidenced by tools and the fossil record].

Does this mean you are certain that DHA automatically enlarges the brain?

Since people haven't examined my article on DHA which I gave a reference too earlier, I'll give the link (http://www.north.londonmet.ac.uk/ibchn/ ... ds1999.pdf) and a quote.

DHA is required for brain
structures and growth. The biochemistry implies that the expansion of the human brain
required a plentiful source of preformed DHA. The richest source of DHA is the marine
food chain while the savannah environment offers very little of it. Consequently H.
sapiens could not have evolved on the savannahs.

From said article. Also an attempt to explain why in general terms concerning mammals to reptiles, birds, etc.

Mammalian brain size is larger in relation to body size compared to the previous egg laying
amphibians, reptiles and fish. The difference could be explained by the evolution of the
placenta. The placenta enables nutrients and energy to be focused continuously on the
development of one or a small number of progeny throughout the critical time of brain
development. In the human, 70% of the calories transferred by the placenta to the fetus is
devoted to brain growth. The placenta is a rapidly growing vascular system with a high
requirement for w6 fatty acids especially AA. In 42 species so far studied, AA and DHA
are major acyl constituents with the precursors being virtually absent. So the emergence of
the w6 fatty acids may have added the missing biochemical link, liberating genetic
potentials for vascular development and hence the evolution of the placenta, mammary
gland and the larger brains of the mammals.

Please notice that we are talking about the womb situation at the time as well.

Explanation on the differences between Australopithecus and Homo Erectus and Sapiens in brain capacity......

Australopithecus spp. are unremarkable in their apparent encephalization throughout their
evolutionary history as far as can be deduced from the fossil record . No australopithecine
has a cranial capacity much over 500 cm3 (7 ), despite the existence of the genus for over 3
Myr. Contrast this to genus Homo, whose cranial capacity doubled from H. erectus to H.
sapiens in a span of at most 1 Myr (Table 1). The Homo spp. fossil evidence and
encephalization quotient (EQ) values do not support a slow, linear Darwinian progession
towards modern intelligence, but rather a sudden, exponential growth of relative brain size
in the last 200,000 years or so.
The earliest evidence for modern H. sapiens is found in Africa. Homo spp. in general are
associated with lake shore (lacustrine) environments in the East African Rift Valley, while
Australopithecines are associated more with forested areas (8,9). Thus far, evidence for
precocious cultural development of Homo sapiens is exclusively confined to lacustrine and coastal marine environments. Lakeshore sites in the Rift Valley have yielded fairly
sophisticated stone tools as old as 260 kyr associated with H. sapiens remains. The
implications of this land/water habitat providing brain specific nutrients has largely been
overlooked.

Just a few things which needed to be raised. So what this is saying is that DHA is the molecule that encourages brain development.

[DavidMcC]

Largenton, I for one, wouldn't deny the truth of your statement concerning the role of fatty acids in brain growth. (BTW, I suspect people didn't read your reference because you hadn't previously given a URL!)
As someone has already pointed out, swimming and diving for fish would not produce the selective pressure for actual evolutionary brain growth, even though the process would have been ebabled by the diet. I'm sure you would agree that brain size increase doesn't come cheap, so there had to be strong pressure for it. That pressure only came in the savanna hunting period, several million years after the proposed semi-aquatic period, therefore, that is when it actually occurred, regardless of the fish content of our diet at the time (the fatty acids do not have to come from fish).

[Largenton]

Can I ask what exact evidence do we have that our evolution took place on the savannahs, when most of the early finds for us come from the Rift Valley? After all, the idea of "Man the hunter" is kindof becoming second place to the other ideas of our development, like Man the Gatherer, Man the Scavenger, etc.

I agree that brain size doesn't come cheap, that is extremely obvious, however, the brain also requires extra DHA to increase the development of it. So there are possibly two factors, the food with those fatty acids to boost brain power and the exertion.

Personally for this I would like to suggest two things. Firstly, an explanation which encompasses both ideas and also another explanation for the brain stimulus.

Now in modern hunter gatherer societies we usually have men doing the hunting and women doing the gathering (if we look at people like the San). The men do an activity which requires concentration, social co-ordination and isn't too reliable, they may not catch anything at all to be honest. The women on the other hand, do the gathering and this is more reliable, you know where the food is meant to be, you can get it quite easily. The article I referenced, suggests that the women collected shellfish which are usually quite numerous. It is entirely possible that the shellfish could be providing that staple in the diet for DHA. Other factors to increase the brain could also be explained by the idea of tool-making, something which, considering the way that homo sapiens make their tools, requires a lot of spatial imagination in order to make the tool in the specific way.

[DavidMcC]

Largenton, the reason given for most of the fossils being in the Great Rift Valley (GRV) is that that is where fossils would be most likely to form, as it usually requires water, and the great rift valley was once a sea (during the early pliocene, which started about 5.3MYa, according to maps published by the Naval Research Labs, Washington, by a certain Leon La Lumiere, and cited by Elaine Morgan in her book, "The Aquatic Ape").
The fact that fossilization generally requires water is used to weaken the aquatic ape hypothesis (AAH), as it implies that it is only because of the need for water to produce fossils that the fossils are found mainly in the GRV, rather than because the hominids stayed with the water. Personally, I think they would have wanted to stay with the water once they found the fresh water of the River Awash (Ethiopia) in any case. The valley of the River Awash lies within part of the GRV. (Adaptation first to sea water, then to fresh water is part of the AAH.)

[DavidMcC]

The question of whether homo actually evolved on the savanna as opposed to by the waterways is a moot point, Largenton. I think it could have been because the water bodies in the savanna might have been as seasonal millions of years ago as they are now.

[Largenton]

One other question, are we talking about the same evolution phase? Because you are mentioning 5.3mya which to me is just slightly out of the range of homo sapiens and erectus which I have been discussing. And despite you saying that it was 5.3 mya, what was it like 2 mya?

I'll admit part of the problem is that fossilisation mostly occurs in those particular regions, however, what about the Tectonic ideas proposed by Bailey...... here

The problem with being on the plains is that for us, we aren't protected. We are slower animals that hunt in the day, not good considering that predators like lions and leopards are around. Bailey makes a good point that the hills of the Rift provide good protection against this, in fact the Hamadryas Baboons use the basalt cliffs of the Rift Valley today to shelter. I think there is more chance that we evolved in Rift Valley as we also refer to the DHA article, most animals that use the savannah adapt in different ways to what we have. What the article also notes is that the people of the Rift Valley have the most diverse mitchondrial DNA of any ethnic group. Please could you read the article I have noted here as most of my argument hinges on that and attacks the Savannah Ape theory.

Please also note that the particular phase I am discussing is not 6mya which the original aquatic ape theory comes from, I am discussing the development of us as a species in this area.

[gwolf]

The question of whether homo actually evolved on the savanna as opposed to by the waterways is a moot point, Largenton. I think it could have been because the water bodies in the savanna might have been as seasonal millions of years ago as they are now.

I think there is a bit more evidence favoring the rift lakes. Little water holes aren't going to have the large fish that the lakes will have. Instead, they'll have killifish. They're tiny, short lived and have eggs that can withstand some drying. I doubt they'd sustain a band of hominids that easily. H. Sapiens also appear to favor the lakes and forests instinctively. Again and again people tell me that walking around in old growth forest "calms them down." They are attracted to the interiors of cathedrals, which duplicate the lighting and trees with narrow stained glass windows and heavy pillars. Also favored are the "moderate" temperatures of the highlands, and the fact that people over and over again have preferred to live near permanent bodies of water. Finally, people who've learned to swim at a young age keep going back to it, even though it may serve no particular function. And whether they like to swim or not, most people also bathe.

People often talk about summer life on a mountain lake as "idyllic." High in the rift valleys, there was such a place with a permanent summertime.

George Wolf