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Author Topic:   why is the lack of "fur" positive Progression for humans?
Blue Jay
Member (Idle past 107 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 166 of 202 (509661)
05-23-2009 11:38 AM
Reply to: Message 163 by RAZD
05-22-2009 9:34 PM


Re: woodland forest apes and bareness selection
Hi, RAZD.

RAZD writes:

That doesn't explain the existence of males with hair similar to females, and they appear to be rather robustly represented in the population.

And females that are hairier than I am are also fairly common in the population.

Over 170 genes are involved in hair morphogenesis(according to this abstract, anyway): you can't expect there to not be noise.

-----

RAZD writes:

If reproduction is not hindered, then the androgen theory fails to explain why the apparent hairlessness of males and females is different.

Except that, curiously enough, the difference is known to be caused by androgens. That's why "androgenic hair" is the technical term for the hair that men grow and women don't.

-----

I have nothing against a sexual selection explanation for hairlessness, but the simple observation is that there are two factors involved: one makes all humans "hairless," and another makes males grow extra hair.

So, there is some mutation that causes both sexes to be equally hairless, which is what you've been asking Drew to produce. But, there is a second genetic mechanism involved, which is a side effect of male hormones. This second mechanism is acted upon by sexual selection. But, this does nothing to show what the first mechanism was for.

In fact, it is consistent with all three hypotheses so far proposed. The aquatic ape hypothesis is faulty for other reasons, but the thermoregulatory hypothesis is still intact.

I am not advocating any one of these models, but I think it should be acknowledged that the dimorphism and the "hairlessness" are not necessarily the same question, and no evidence so far presented is able to link them. Your evidence still has not explained the first mechanism.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


This message is a reply to:
 Message 163 by RAZD, posted 05-22-2009 9:34 PM RAZD has responded

Replies to this message:
 Message 175 by RAZD, posted 05-24-2009 11:45 AM Blue Jay has responded

  
arrogantape
Member (Idle past 2050 days)
Posts: 87
Joined: 09-26-2008


Message 167 of 202 (509667)
05-23-2009 12:41 PM
Reply to: Message 165 by lyx2no
05-23-2009 1:24 AM


Re: The Question Is
lyx2no,

You used Penguins to counter what the scientists wrote. I ran with that, because I think penguins look clowny, not that I really thought they looked like a penguin, with bunyons yet.... geees.

It was reported that with such large flat feet, H floresiensis had to walk like a clown. I post things from a variety of sources. They, in turn, quote Nature. New Science is a reporting site for breaking news in science. Yes they write in the vernacular.

Try fitting your feet with skin diving fins. This is an exaggeration, but you would find you have to lift your knee high. You would be ungainly. H f. could not defend themselves against big cats. There were plenty of those inland over the globe, except isolated islands.

H habilis remains are found with big cat' trash. Small 3-4 footers with simple rock tools, would be a lot better off avoiding carnivores whenever possible.

They were a strong swimmer.

h Floresiensis swam to the Island. That is a long swim, and not one for novices. Since there has been occupation on Flores for 800,000 years some early hominid made the swim.

If the anthropologists make it back to that island, and caves anywhere around the region, perhaps we can have some questions answered. I would like to see a skeleton 800,000 years old.


This message is a reply to:
 Message 165 by lyx2no, posted 05-23-2009 1:24 AM lyx2no has responded

Replies to this message:
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bluescat48
Member (Idle past 1598 days)
Posts: 2347
From: United States
Joined: 10-06-2007


Message 168 of 202 (509668)
05-23-2009 1:27 PM
Reply to: Message 167 by arrogantape
05-23-2009 12:41 PM


Re: The Question Is
h Floresiensis swam to the Island. That is a long swim, and not one for novices. Since there has been occupation on Flores for 800,000 years some early hominid made the swim.

Could you provide any credible evidence that florensis swam to flores from Africa?


There is no better love between 2 people than mutual respect for each other WT Young, 2002

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Since Evolution is only ~90% correct it should be thrown out and replaced by Creation which has even a lower % of correctness. W T Young, 2008


This message is a reply to:
 Message 167 by arrogantape, posted 05-23-2009 12:41 PM arrogantape has not yet responded

    
lyx2no
Member (Idle past 2125 days)
Posts: 1277
From: A vast, undifferentiated plane.
Joined: 02-28-2008


Message 169 of 202 (509669)
05-23-2009 1:29 PM
Reply to: Message 167 by arrogantape
05-23-2009 12:41 PM


Re: The Question Is
Hi aa

We both hit the submit reply button at the same time (12:41). You were replying at the same time I was saying no need to reply. I'll keep this short and not add anything to give you cause to reply again.

I ran with that
Yeah, I like to use off the wall examples because folks are less prone to confusing the example with the argument. I couldn't count the number of times I've used a prosaic example only to find the person I was arguing with thought my interest lie in the example. Plus they're fun.

Try fitting your feet with skin diving fins. This is an exaggeration
It's a good metaphor, but my concern would be that It may be much more of an exaggeration then it would seem at first glance. Not merely due to size but also to a lack of kinesthesia. H. floresiensis would have grown up with their feet and understood how to use them as fluidly as we used our stubby, ice skate feet.

h Floresiensis swam to the Island.
Not to mention that I'd gone far astray in my own concern which was, "How do you come to this conclusion?". But that would be another thread.

Sorry for the intrusion, folks.


It is far easier for you, as civilized men, to behave like barbarians than it was for them, as barbarians, to behave like civilized men.
Spock: Mirror Mirror

This message is a reply to:
 Message 167 by arrogantape, posted 05-23-2009 12:41 PM arrogantape has not yet responded

  
arrogantape
Member (Idle past 2050 days)
Posts: 87
Joined: 09-26-2008


Message 170 of 202 (509671)
05-23-2009 1:34 PM


Bluescat, come on, you must be joking. It was a migration, performed over generations.
Replies to this message:
 Message 171 by bluescat48, posted 05-23-2009 2:57 PM arrogantape has responded

    
bluescat48
Member (Idle past 1598 days)
Posts: 2347
From: United States
Joined: 10-06-2007


Message 171 of 202 (509672)
05-23-2009 2:57 PM
Reply to: Message 170 by arrogantape
05-23-2009 1:34 PM


I agree that it was a migration what I am asking is where is evidence of swimming?


There is no better love between 2 people than mutual respect for each other WT Young, 2002

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Since Evolution is only ~90% correct it should be thrown out and replaced by Creation which has even a lower % of correctness. W T Young, 2008


This message is a reply to:
 Message 170 by arrogantape, posted 05-23-2009 1:34 PM arrogantape has responded

Replies to this message:
 Message 172 by arrogantape, posted 05-23-2009 9:13 PM bluescat48 has responded

    
arrogantape
Member (Idle past 2050 days)
Posts: 87
Joined: 09-26-2008


Message 172 of 202 (509692)
05-23-2009 9:13 PM
Reply to: Message 171 by bluescat48
05-23-2009 2:57 PM


The evidence is that it swam to Flores Island. Another thing that has me excited are the big flat feet. This is a very archaic condition. Not having the specialty bone needed to create an arch left it with a big chimp foot. H f. also has a primitive wrist bone that matches that of H habilis, known from some incomplete specimens in Africa. H habilis is about the same size as H floresiensis. That would mean there was no need for it to be a shrunk H erectus. Besides, H erectus had a modern wrist, and feet.
This message is a reply to:
 Message 171 by bluescat48, posted 05-23-2009 2:57 PM bluescat48 has responded

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bluescat48
Member (Idle past 1598 days)
Posts: 2347
From: United States
Joined: 10-06-2007


Message 173 of 202 (509696)
05-23-2009 11:09 PM
Reply to: Message 172 by arrogantape
05-23-2009 9:13 PM


The evidence is that it swam to Flores Island.

What evidence all you are saying is that they swam there? What evidence that they didn't walk there over the course of 20,000 years. Flat feet or no flat feet.


There is no better love between 2 people than mutual respect for each other WT Young, 2002

Who gave anyone the authority to call me an authority on anything. WT Young, 1969

Since Evolution is only ~90% correct it should be thrown out and replaced by Creation which has even a lower % of correctness. W T Young, 2008


This message is a reply to:
 Message 172 by arrogantape, posted 05-23-2009 9:13 PM arrogantape has not yet responded

    
Meddle
Member
Posts: 159
From: Scotland
Joined: 05-08-2006


Message 174 of 202 (509698)
05-23-2009 11:17 PM
Reply to: Message 172 by arrogantape
05-23-2009 9:13 PM


That Nature article...
Another thing that has me excited are the big flat feet. This is a very archaic condition. Not having the specialty bone needed to create an arch left it with a big chimp foot.

I found the Nature article on the analysis of H.floresiensis feet being hosted on the institution website of one of the authors. Although H.floresiensis feet are indeed large compared to modern humans, the relative proportions of the feet are comparable to bonobos, which are smaller than the common chimpanzee. While your earlier comparison of the size of feet being akin to 'skin diving fins' was as you say an exaggeration, it would appear to be misleading.

Edited by Malcolm, : No reason given.


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 Message 172 by arrogantape, posted 05-23-2009 9:13 PM arrogantape has not yet responded

  
RAZD
Member
Posts: 18455
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.9


Message 175 of 202 (509755)
05-24-2009 11:45 AM
Reply to: Message 166 by Blue Jay
05-23-2009 11:38 AM


Re: woodland forest apes and bareness selection
Hi Bluejay,

As Jon (Message 164) has pointed out, the sexual selection was for young appearing females, rather than hairlessness per se, the logical result is that selection is NOT for bare, just the hair pattern of children in females, which explains the retention of vellus hair on females as well as on males, while the terminal hairs are selected against in females but not in males.

We have other evidence of the selection for youthful appearance as neoteny also explains the retention of the youthful face shape in humans, the face shape you see in young chimpanzees and gorillas, and to a lesser extent in the older hominids.

Studies have shown that this desire for youthful appearing female mates is still strong today, so we have evidence of an active mechanism, we have evidence of how that mechanism operates, and we don't need to propose some additional mechanism, especially an additional mechanism that is at variance with the fossil evidence AND at variance with the existing pattern of hair development.

See Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution thread again (message 1):

quote:
This is observed in many species, and in humans there are several theories on the issue of "beauty" but one of the consistent factors involved is that the more beautiful faces are averaged (see average face-ness: click) -- more on this in humans later.
...
The question can also be investigated by what is considered beautiful (women) or handsome (men) and does it show a skewed pattern. This goes back to the average face issue raised above: "average face-ness" was not enough to fully explain the whole pattern in the experiment as there was also a clear bias in the data for youth (see babyface-ness: click), and the summary comments on this include these statements (read Summary: click for the whole summary):
(1) The results of our study are quite surprising. Compound (i.e. morphed) faces were, on average, regarded as being more attractive than the original faces. ...
(2) For female faces, it could be shown that babyface attributes - such as large, round eyes, a large domed forehead and small, short nose and chin lead to a rise in attractiveness values.
(3) To sum up, our study shows clearly that the most attractive faces do not exist in reality, they are morphs, i.e. computer-created compound images you would never find in everyday live. These virtual faces showed characteristics that are unreachable for average human beings.

They also found "averaged" but not "babyfaced" beauty applied to males and thus it looks like human beauty involves both and (average individual icon} for many features and a skewed {extreme individual icon} tending towards idealized younger looking sexually mature females. That this also demonstrates the same pattern of run-away sexual selection noted for breasts, buttocks and bareness is not likely to be an accident.

Over 170 genes are involved in hair morphogenesis(according to this abstract, anyway): you can't expect there to not be noise.

So any one of them could have been used to produce the effect of bare skin rather than the one that was chosen by selection. Any one of them could have been used to promote universal bare skin, if that is what the driving selection mechanism was finding beneficial. That none of them were actually selected to produce bare skin, leads to the logical conclusion that bare skin was not the desired result.

Except that, curiously enough, the difference is known to be caused by androgens. That's why "androgenic hair" is the technical term for the hair that men grow and women don't.

Which causes the "desired" result - younger appearing women that have still retained juvenile pattern hair. As noted before, arrested development is a common result in many species, when reproductive ability is reached before a feature is fully formed. This too is logical, as then the energy is put into reproduction rather than further development of the already reproductively successful organism.

I have nothing against a sexual selection explanation for hairlessness, but the simple observation is that there are two factors involved: one makes all humans "hairless," and another makes males grow extra hair.

Males do not grow extra hair, they have retained more of what would be normal hair if selection for female appearance were not involved. The male patterns of hair is due to combination of non-selection in males (so retained hair features are selected out) and cross-over effects where males inherit the result of selection in females.

So, there is some mutation that causes both sexes to be equally hairless, which is what you've been asking Drew to produce.

But male bareness has not been selected for, as there are plenty of phenotypes available to produce the effect while hairy patterns are still evident in the population, nor do we see any continued selection effect for bareness in males the way we do in females.

But, there is a second genetic mechanism involved, which is a side effect of male hormones. This second mechanism is acted upon by sexual selection. But, this does nothing to show what the first mechanism was for.

No, there is one selection force acting on a number of genes, with positive result in females and non-relational results for males.

In fact, it is consistent with all three hypotheses so far proposed.

Only one of which explains all the evidence. The "Savannah" theory can be ruled out because it doesn't explain features that evolved before the Savannah ecology. Hair loss in other cursorial hunters in the same environment does not occur (see dogs), so it is contradicted by other evidence.

Similar for the aquatic ape theory: it is contradicted by sexual dimorphism in hair patterns.

The aquatic ape hypothesis is faulty for other reasons, but the thermoregulatory hypothesis is still intact.

One other reason being a complete absence of any supporting evidence.

But it is not a thermoregulatory hypothesis, it trys to explain the loss of a thermoregulatory feature. That seals and otters are perfectly capable of thermoregulation with full fur shows that this argument does not explain the retention of fur in these organisms.

I am not advocating any one of these models, but I think it should be acknowledged that the dimorphism and the "hairlessness" are not necessarily the same question, and no evidence so far presented is able to link them. Your evidence still has not explained the first mechanism.

Ok, then add this up:

  • No loss in the number of hairs in either males or females. This rules out any selection for loss of hair. ::Not explained by aquatic adaptation.
  • What is selected is arrested development of hair at a juvenile pattern, similar to many other features selected (see neoteny above). ::Not explained by aquatic adaptation.
  • Terminal hair on female legs is still part of the modern pattern of hair development. This is the part most in the water, the part under high drag when kicking during swimming -- ie this pattern in women is not consistent with the aquatic adaptation conjecture (while none of the male pattern is consistent with the aquatic ape conjecture). ::Not explained by aquatic adaptation.
  • Selection for younger and barer appearing women is still very active in our population, as would be expected for a run-away sexual selection mechanism.} ::Not explained by aquatic adaptation.
  • Humans living in coastal ecologies since prehistoric times show no additional adaptation nor retention of any feature that is of benefit to living in that ecology compared to Tibetans as a control. ::Not explained by aquatic adaptation.
Sexual selection explains all the evidence, it is consistent with the fossil evidence, it is consistent with the hair patterns in chimpanzees and gorillas, especially while breast-feeding.

Enjoy.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
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This message is a reply to:
 Message 166 by Blue Jay, posted 05-23-2009 11:38 AM Blue Jay has responded

Replies to this message:
 Message 176 by Blue Jay, posted 05-25-2009 12:09 PM RAZD has responded

  
Blue Jay
Member (Idle past 107 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 176 of 202 (509837)
05-25-2009 12:09 PM
Reply to: Message 175 by RAZD
05-24-2009 11:45 AM


Re: woodland forest apes and bareness selection
Hi, RAZD.

RAZD writes:

Bluejay writes:

Over 170 genes are involved in hair morphogenesis(according to this abstract, anyway): you can't expect there to not be noise.

So any one of them could have been used to produce the effect of bare skin rather than the one that was chosen by selection. Any one of them could have been used to promote universal bare skin, if that is what the driving selection mechanism was finding beneficial. That none of them were actually selected to produce bare skin, leads to the logical conclusion that bare skin was not the desired result.

Lots of things could have been, but arent. You cant make an argument about evolution from what didnt happen unless you accept teleology as a valid explanatory framework.

The fact is that one mutation did happen, and it would have worked well enough: theres no reason to think that something else should have happened. You dont need bare skin to improve the efficiency of perspirative cooling over hairy skin.

Besides, I can turn it back on you: If the fact that were not completely bare disproves the evaporative cooling hypothesis, then how does the fact that men are generally less attracted to 12-year-olds than to 20-year-olds not disprove sexual selection for younger-looking females?

You dont have to take everything to the extreme to make it work.

-----

RAZD writes:

But male bareness has not been selected for, as there are plenty of phenotypes available to produce the effect while hairy patterns are still evident in the population, nor do we see any continued selection effect for bareness in males the way we do in females.

If you take away a male's ability to produce or respond to androgens (testosterone specifically, I think), you get a male (usually underdeveloped and feminized) with female pattern body hair (here is Wikipedia on the subject). So, the dimorphism in hair pattern is due to a hormonal mechanism. That the non-androgenic pattern of body hair in humans is different from the typical pattern for other apes shows that something else (independent of androgenic dimorphism) caused our hairs development to be arrested before the terminal stage.

It might be sexual selection for younger-looking females that is secondarily inherited by males.
It might be natural selection for increased efficiency in perspirative cooling.

The obvious answer is that the dimorphism does not need to be explained by whatever this mechanism turns out to be, because the dimorphism already has an independent explanation that can very readily and easily be observed.

So, you need to produce evidence other than dimorphism to show that our relatively underdeveloped hair is due to sexual selection.

-----

That males have no stabilizing selection for a specific amount of body hair is also meaningless, because we havent lived on the savannahs for a long time. However, I would like to point out that there is a difference in mean hairiness between African and Caucasian men, which is consistent with the savannah hypothesis.

It could indicate that Caucasians started growing more hair after they went to Europe, or that there was continued selection in Africa for males to be less hairy (either sexual or natural selection may be the case). But, whatever the case, it is not explained by sexual dimorphism.

-----

RAZD writes:

The "Savannah" theory can be ruled out because it doesn't explain features that evolved before the Savannah ecology.

What features evolved before the savannah ecology?
And, what do these features have to do with the loss of terminal hair in humans?

-----

RAZD writes:

Hair loss in other cursorial hunters in the same environment does not occur (see dogs), so it is contradicted by other evidence.

Why doesnt the observation that dogs, hyenas and cats dont sweat fully explain the disparity?

Homo is the only alleged cursorial hunter on the savannah that uses evaporative cooling as a major thermoregulatory mechanism on its entire body, and thus, is the only cursorial hunter who stands to gain thermoregulatory advantages from losing its terminal hair.

The appeal to other cursorial hunters as negative evidence fails.

-----

RAZD writes:

Ok, then add this up:
No loss in the number of hairs in either males or females. This rules out any selection for loss of hair. ::Not explained by aquatic adaptation.
What is selected is arrested development of hair at a juvenile pattern, similar to many other features selected (see neoteny above). ::Not explained by aquatic adaptation.
Terminal hair on female legs is still part of the modern pattern of hair development. This is the part most in the water, the part under high drag when kicking during swimming -- ie this pattern in women is not consistent with the aquatic adaptation conjecture (while none of the male pattern is consistent with the aquatic ape conjecture). ::Not explained by aquatic adaptation.
Selection for younger and barer appearing women is still very active in our population, as would be expected for a run-away sexual selection mechanism.} ::Not explained by aquatic adaptation.
Humans living in coastal ecologies since prehistoric times show no additional adaptation nor retention of any feature that is of benefit to living in that ecology compared to Tibetans as a control. ::Not explained by aquatic adaptation.

Youre talking to Bluejay now, not Arrogantape: I have already rejected the aquatic ape hypothesis.

Note also: I acknowledge that there is no loss in the number of hair follicles. However, I will continue to use the terms hairless, bald and hair loss (always in quotation marks) to refer to the defecit of terminal hair, because underdeveloped hair and arrested development of terminal hair make very awkward sentences. But, know that this is not a point of contention between us.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


This message is a reply to:
 Message 175 by RAZD, posted 05-24-2009 11:45 AM RAZD has responded

Replies to this message:
 Message 177 by RAZD, posted 05-25-2009 4:21 PM Blue Jay has not yet responded
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RAZD
Member
Posts: 18455
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.9


Message 177 of 202 (509867)
05-25-2009 4:21 PM
Reply to: Message 176 by Blue Jay
05-25-2009 12:09 PM


Re: woodland forest apes and bareness selection
Hi again Bluejay,

Lots of things could have been, but arent. You cant make an argument about evolution from what didnt happen unless you accept teleology as a valid explanatory framework.

The fact is that one mutation did happen, and it would have worked well enough: theres no reason to think that something else should have happened.

Agreed. It's the old forensic question/s of "means, motive and opportunity" to figure out what most likely occurred in the past.

We could say that the means is genetic mutations, the motive is natural selection for increased ability to survive and reproduce, and the opportunity is an ecology where the changes can take effect (or we could say that the mutations provide the opportunity, natural selection provides the means, and the ecology provides the motivating force - your pick). We also need to explain all the evidence, not just what happened, but the timeline for when it happened.

You dont need bare skin to improve the efficiency of perspirative cooling over hairy skin.

Which does not explain why horses sweat (profusely) and yet there are no bare horses I am aware of. Thus perspiration does not explain the arrested development of hair, nor does it explain why females would be more affected than males.

Instead we see that ecrine glands are already existing on the chests of other apes, and thus are most likely to exist on out common ancestors -- ie the ability to sweat pre-dates the division of humans from chimpanzees and gorillas, although at that stage it was used to keep bare-ish skin soft and supple, as in on breasts during feeding (as seen in chimps and gorillas).

Besides, I can turn it back on you: If the fact that were not completely bare disproves the evaporative cooling hypothesis, then how does the fact that men are generally less attracted to 12-year-olds than to 20-year-olds not disprove sexual selection for younger-looking females?

Pedophiles and child pornography do show that some men are much more attracted to 12-year-olds than to 20-year-olds. You also have many cultures where marriages take place with 12-year-old women and old(er) men.

The fact remains that IF cursorial hunting and the sweating ability of the hunter causes selection for bare skin, that then the barer sex should be the one doing the hunting.

You dont have to take everything to the extreme to make it work.

I'm not taking it to the extreme, rather I'm looking at the evidence that selection has gone to one extreme end in hair development in women, and I note that this is one of the signs of runaway sexual selection. Then I note that this pattern is not extreme in men.

Don't you agree that a species with a more advanced selected feature would the one more affected by selection process?

If you take away a male's ability to produce or respond to androgens (testosterone specifically, I think), you get a male (usually underdeveloped and feminized) with female pattern body hair (here is Wikipedia on the subject). So, the dimorphism in hair pattern is due to a hormonal mechanism. That the non-androgenic pattern of body hair in humans is different from the typical pattern for other apes shows that something else (independent of androgenic dimorphism) caused our hairs development to be arrested before the terminal stage.

If you block the males ability to produce testosterone altogether the default pattern of development is female, complete with fully formed female genitalia and breasts (just no fallopian tubes or ovaries). So if you block normal male development, you are left with development inherited via the X gene from females.

Curiously this "default" pattern of development includes the female hair patterns as have been selected in females, and thus - again - showing that the selection occurred in the female genes and that any effect on males is what they inherit from the selection in females.

It might be sexual selection for younger-looking females that is secondarily inherited by males.
It might be natural selection for increased efficiency in perspirative cooling.

So then why are the running sweating hunters less affected by this selection than the non-running non-hunting gatherers and protectors of children? This is why the Savannah fails to explain the evidence: the selection should be more extreme in the males and it isn't.

Males are probably significantly less effective at cooling than females, due to body mass to surface skin ratios, while at the same time exercising more?

However, I would like to point out that there is a difference in mean hairiness between African and Caucasian men, which is consistent with the savannah hypothesis.

But not with Tibetans, who have less hair than Africans.

What features evolved before the savannah ecology?

Bipedal gait is one that is now generally accepted to pre-date the Savannah theory. This used to be the major argument for the theory.

The existence of bare skin in other closely related apes means that the common ancestor likely had bare skin areas, particularly on the chest, and especially on the female breasts. Thus this likely predates the split of humans and chimps and gorillas.

These bare areas are kept soft and supple through moisture from the ecrine glands that cover the chests of these apes, but not of older common ancestor apes, where they are limited to hands and some other specific areas. These same glands are what are now developed on humans to cover more areas and used for one form of thermoregulation via sweat.

Thus both bipedal gait and some bare skin areas protected by proto-sweat glands pre-date the Savannah. This gave the upright barechested hominid a pre-adapted advantage when the Savannah ecology arose: it could extend it's territory into the open patches and still survive happily in the wooded jungle groves -- where, not incidentally, fossil evidence places them.

Cursorial hunting does not require, nor necessarily benefits from, replacing fur with arrested hair development.

Sweating horses do not require, nor would they necessarily benefit from, loss of hair (would a completely shaved horse run faster or longer?)

Homo is the only alleged cursorial hunter on the savannah that uses evaporative cooling as a major thermoregulatory mechanism on its entire body, and thus, is the only cursorial hunter who stands to gain thermoregulatory advantages from losing its terminal hair.

So why don't horses, that sweat, lose their hair in order to survive being caught by wolves, cursorial hunters with fur? If it was a superior method or a survival benefit of any kind, then why are there NO bare horses, while horses that have bare spots are considered diseased? Why aren't racing horses shaved?

http://answers.yahoo.com/question/index?qid=20090111144941AAicK0W

Youre talking to Bluejay now, not Arrogantape: I have already rejected the aquatic ape hypothesis.

Note also: I acknowledge that there is no loss in the number of hair follicles. However, I will continue to use the terms hairless, bald and hair loss (always in quotation marks) to refer to the defecit of terminal hair, because underdeveloped hair and arrested development of terminal hair make very awkward sentences. But, know that this is not a point of contention between us.

And "apparent bareness" is also awkward. Nonvisible hair?

Question: why do "blonds have more fun" -- how do blonds evolve in a cursorial hunting or aquatic ape or sexual selection model?

Enjoy.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 176 by Blue Jay, posted 05-25-2009 12:09 PM Blue Jay has not yet responded

  
RAZD
Member
Posts: 18455
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.9


Message 178 of 202 (510125)
05-27-2009 10:30 PM
Reply to: Message 176 by Blue Jay
05-25-2009 12:09 PM


Sequential evolution rather than multiple at once features
Hi Bluejay,

Just adding another element to the discussion: timing.

To me the major problem with the Savannah Theory is timing - several things have to evolve at the same time for it to work: the bareness plus sweating to regulate heat during the day to prevent hyperthermia and the subcutaneous fat layer to regulate heat during the night to prevent hypothermia. And it has to be done in a short period of time, as the evidence shows hominids expanding with the Savannah.

Much easier to envisage evolution of bare areas as sexual signalling, this being enhanced by upright posture, and the expansion of ecrine glands in the increasing bare areas. The wooded forest and the pre-Savannah climate means that the nights are not cool enough to need the warmth of the subcutaneous fat layer, and this evolves later after the bareness has expanded to the point where it is needed, and as the climate changes. Then the ecrine glands become more versatile as sweat glands when the hominids move into the Savannah, pre-adapted to take advantage of the opportunity.

Enjoy.


we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

This message is a reply to:
 Message 176 by Blue Jay, posted 05-25-2009 12:09 PM Blue Jay has responded

Replies to this message:
 Message 179 by Blue Jay, posted 05-28-2009 12:57 PM RAZD has acknowledged this reply
 Message 180 by Blue Jay, posted 05-31-2009 11:14 PM RAZD has responded

  
Blue Jay
Member (Idle past 107 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 179 of 202 (510186)
05-28-2009 12:57 PM
Reply to: Message 178 by RAZD
05-27-2009 10:30 PM


Re: Sequential evolution rather than multiple at once features
Hi, RAZD.

Sorry I'm taking so long on this. I'm trying to get a reply together, but it's turning out to be a lot more work than I really want to put in to EvC, and my field work is starting to pick up now that the rain is gone.

But, I'll have some stuff to present soon (probably not nearly as spectacular as I want it to be, though).

Thanks.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


This message is a reply to:
 Message 178 by RAZD, posted 05-27-2009 10:30 PM RAZD has acknowledged this reply

  
Blue Jay
Member (Idle past 107 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 180 of 202 (510512)
05-31-2009 11:14 PM
Reply to: Message 178 by RAZD
05-27-2009 10:30 PM


Re: Sequential evolution rather than multiple at once features
Hi, RAZD.

Sorry I took so long on this: it took me this long to solidify my thoughts.

Here is my argument against sexual selection as the mechanism for hairlessness in humans:

Human males do not have a random distribution of body hair patterns. Asian males are predominantly hairless, and Caucasian males are predominantly hairy. African males are intermediate, having both hirsute and bare patterns. This 1960s study has the hairiest and barest chest hair patterns being the two most common groups in African American men, creating a bimodal pattern, which could suggest disruptive selection, in which both hairiness and bareness are selected for.

Interestingly, when you look even closer, you see a different picture. The earliest living branches of humanity, the Khoisan and Pygmies, have very bare-chested males (Google "Khoisan people" or "pygmies" and count how many hairy-chested males you see: none of them wear shirts, so it's easy to tell), and its actually the later-branching groups that account for the hairiness in African males. This implies that bareness is the initial condition for male Homo sapiens, and that hairiness in males is atavistic. Thus, the atavistic hairiness of males explains the dimorphism, not the hairlessness of females.

Thus, while sexual selection for bare skin seems to be prevalent today, and may very well be the cause of sexually dimorphic hair patterns in Caucasians, it couldnt possibly have been the primal cause, because early Homo sapiens were not sexually dimorphic in terms of body hair patterns.


-Bluejay (a.k.a. Mantis, Thylacosmilus)

Darwin loves you.


This message is a reply to:
 Message 178 by RAZD, posted 05-27-2009 10:30 PM RAZD has responded

Replies to this message:
 Message 181 by RAZD, posted 06-04-2009 10:59 PM Blue Jay has not yet responded

  
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