The aquatic theory uninterrupted?

[Bernt]

Here it goes again, I am not a person who easily gives in to people obstructing my search for information. Now I hope all the saboteurs will stay in the last thread if they have more at heart. It may be a long shot, but well, let us all hope.

Possible aquatic adaptions in man: All compared to chimps and other relevant mammals.

-Body hair
-Subcutanous fat
-Diving reflex
-Prefrence for watery environments
-Breath control

I may have missed some from the previous thread, so those who feel important ones have been left out, post. What evidence indicates these traits qualifying as aquatic adaptions, and what other functions may they eventually have served?

Punctuated equilibrium vs gradual evolution may be relevant if (as I asked many times) it could account for something regarding the aquatic theory (both pro or con) which gradualism cannot. If not, the issue should be debated elsewhere.

 

[CEngelbrecht]

Additions:
-Preference for sexual conduct
-Offspring behavior
-Bipedal

 

[CEngelbrecht]

Addition:
-Aquatic adaptation of hair & limbs

 

[Bernt]

So the total list would be:

-Body hair
-Subcutanous fat
-Diving reflex
-Prefrence for watery environments
-Breath control
-Preference for sexual conduct
-Offspring behavior
-Bipedalism
-Aquatic adaptation of hair & limbs

 

[Bernt]

Lets discuss them one at a time?

What evidence is there for lack of fur (little body hair) being an aquatic adaption?

CEngel wrote: "* The lack of fur doesn't work on the Savannah unless you are very big (like the elephant or rhino). The use of fur in the water only works when you're very small (like the otter). The human size is in between. * The lack of fur and presence of the fat layer speaks for the AAP. Also, the turn of the hairs on the human body is quite different from the rest of the Pan group. Each of you, look at your lower arm: The hairs turn slightly away from the elbow and to the outer side. On the chimp the hairs grow up towards the elbow. This is to indicate that the human hairs have turned to fit the swimming moves and the course of the water across the skin.

-So since humans are not big enough to profit from lack of fur on land, and not small enough to profit from fur in the water, the lack of fur is an aquatic adaption... Perhaps... but if and only if we do not find other good candidates for adaptive value of lack of fur in our ancestors. May lack of fur have come about as a result of wearing of clothes perhaps, making us able to take on and off fur when needed? I need more evidence to be convinced.

-The point about human hairs having turned to fit swimming moves and this being an aquatic adaption seems problematic. First we need to know of a function of the hairs turning/ their angle. Do they increase swimming speed? If I shaved them off and/or glued on hairs with different profiles, would you be able to measure any difference in aquatic ability? If not, how do they function? Evolution would not select for anything that does not lead to increased survival/ reproduction. Alternatively they may just be random, or a byproduct of another adaption.

 

[Kim Eslinger]

Swimmers shave the hair off their bodies to enhance their speed in the water...thus the adaptation of thinning hair would be a speed adaptation, not necessarily a survival issue.

 

[Erik]

Wouldn't speed be directly related to survival? Faster means better able to eat, and better able to avoid being eaten.
Eric F was saying something about hairs on the human body helping to initiate the MDR.
Cheers,
Erik Y.

 

[efattah]

Other things which need to be considered:

- Hypoxia induced blood shift/bradycardia (i.e. dive reflex without immersion)
- Sweat based cooling system is extremely inefficient when it comes to conservation of water; humans must live near massive sources of fresh water, unlike animals
- Some people say the webbing between the fingers and toes is a sign
- Here's another one: 40m limit for scuba diving is no coincidence, but corresponds exactly to the maximum practical breath-hold diving depth. Think about this--it may not be obvious at first, then you'll understand.
- Prevalence of myopia in the world: something like 60% of the world is myopic, and no other organ has such a poor success rate; all marine mammals are myopic on the surface because myopia on the surface makes your vision better underwater; myopia on the surface is also extremely unfavourable for survival in the savannah
- Remember the recent study of those diving children who could see amazingly well underwater



Eric Fattah
BC, Canada

 

[Bernt]

Swimming speed is increased by shaving (not much but enough to be measured), but Engels argument is that the remaining hair on our arms for instance is a swimming adaption. Shaving those hairs off would reduce swimming speed if this were true. In my view the remaining hairs do not stand strong as an adaption.

 

[Kim Eslinger]

Precisely my point.

 

[Erik]

Ahhh....sorry I missed that Kim.
Cheers,
Erik Y.

 

[Roan]

I'm a little confused. When Bernt & others in these two (I think provocative and very entertaining) threads have written about hair for aquatic adaptation only working on small mammals (otters); what about seals and sea lions? I believe their hair helps to insulate them from cold as well as provides a complete barrier to water coming in much contact to their skin. I think they evolved from an already haired proto-bear; but why would'nt an evolving aquatic ape develop hair like our pinniped friends? Given the great efficiency with which cold water conducts temperature (warmth) from out of our nekid bodies would'nt our relative lack of hair argue against an aquatic ape?

 

[efattah]

Correct me if I'm wrong, but most seals & sea lions evolved in cool/cold water, while humans (according to the aquatic ape theory) evolved in 28-30C water.

Fur usually only found in cold water species....?


Eric Fattah
BC, Canada

 

[Bernt]

Possible reasons why we lack fur:
1. Aquatic adaption. Function: Increase swimming speed (reduce drag).

2. Better thermoregulation. History: Culture/Clothes possibleized taking weather protection on and off in response to different weather.

3. Thermoregulation on land as a result of bipedal locomotion in the open. I.e sweating instead of panting.

Which should we choose and why?

 

[Roan]

I can accept that about the aquatic ape theory: that it happened in relatively warm waters, hence the lack of hair or fur. However, there is a Hawaiian Monk Seal and there were both a Carribean and a Mediterranean Monk Seal :waterwork that are now extinct. They haul out on warm beaches fully furred and said fur does not slow them down in the water. Perhaps they retained their fur after evolving in colder climes and spreading out to warmer areas. It seems depending on how much time our aquatic buddy spent in the water and of course how warm or cold it was, insulation would be a main concern. Are we talking about an aquatic ape who was almost seal-like in the amount of time spent in the water or more like a gatherer at the seashore? I read somewhere that in time of Early Man, women were the gatherers at the seashore, thus their thighs and hips are more endowed with "insulation."

Seriously though, that is perhaps my question: exactly how aquatic was this ape? Could humans ever really swim fast enough (fins or not) for the loss of hair to really matter enough for that adaptation to take place? I'd appreciate responses to any of my questions/points that are relevent to the thread. I'll also review previous posts and perhaps I'll look up the original (Hardy) sources.

 

[efattah]

Another point is the shape of the human nose, sloped downward like that of the probiscus monkey, and unlike other apes (preventing water in the nostrils).

Eric Fattah
BC, Canada

 

[Shadowkiller]

Incidentally it is the size of the human nose, and its outward bend that is "blamed" for the large mammary glands of the human female...:hmm
Other primates have much flatter nostrils, thus the infant is not as prone to accidental suffocation.

Anyway the point being, that a larger nose must have a serious advantage, otherwise it would not be selected for. Wether that implies an aquatic adaption is conjecture since modern humans don't look much like our ancestral "chimp".

Living near (not necessarily in) the ocean has the bonus of providing mental stimulation (shapes, motion, materials) as well as the necessary food for building larger brains.

The Terry Pratchett Book "The Science of Discworld" covers this subject too I think...

 

[kenten]

i remember something about women breasts having no necessitiy for being so big unlike other apes.
may there be some aquatiq explanation for this other than aesthetics

one more proof for aquatic adaptation was the use of vocal cords by being able to control breath

 

[Will]

A couple of points,

Digital webbing is result of a developmental malfunction. A hand or foot starts out as essentially a paddle, which undergoes controlled atrophy between the bones to become digitised.

If we're talking about hair, we have to mention the abundant growth we have on our heads in comparison to everywhere else. I can't see any evolutionary benefit for the aquatic ape in this.

 

[Shadowkiller]

Originally posted by kenten
i remember something about women breasts having no necessitiy for being so big unlike other apes.

They are necessary so our infants don't have their noses squashed and suffocate. A flat nose, like that of a chimp doesn't have that problem. Flat breast, flat nose means that the nostrils will be blocked. The shape of the human female breast allows space for the infants nostrils to remain clear.

Not sure what that has to do with water...
I doubt very much if the early humans were great divers. Much more likely they were sea shore scavengers, with the occasional bobbing for shellfish thrown in.