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Junior Member (Idle past 5862 days) Posts: 12 From: Schererville, IN Joined: |
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Author | Topic: why is the lack of "fur" positive Progression for humans? | |||||||||||||||||||||
RAZD Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Thanks Bluejay, I hope my delayed response is not too late.
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 it’s 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. Interesting. However, I have several problems here, not least of which is that I have not said there is no effect on males. First, where there is more disadvantage to the loss of hair I would expect survival selection of atavistic growth to occur, except where it was suppressed by continued selection. If sexual selection was recent comparatively then there should also be some groups with more than average atavistic women, and I would expect those groups to correlate with male atavistic growth -- if the selection for a return to heavier hair growth was an advantage. I would expect this in Tibet and the pole areas. Second, curiously, I would expect the earliest living branches to show the most complete development of less visible hair, especially in an environment where it was not a significant disadvantage. I would expect to see the most compensatory systems to counter the disadvantages of less visible hair, and thus I would also expect to see the most cross-over of effects from selection in one sex to the other in a trait that is not sex-linked. Without any selection pro or con on hair visibility in men I would expect that over time they would tend to become less visible as well, just because of the shared genes. Thus every mutation that promoted less visible hair in females would be selected, and the male offspring would inherit all the mutations not bound to sexual differentiation. Remember, that while they may represent an old lineage, this does not mean that they have not continued to evolve from a common ancestor population, so this muddies the picture. Third, I would also expect the same pattern in other "earliest living branches" and a correlation to the divergence of human population as it spread across the globe for consistency. http://news.nationalgeographic.com/...13_journeyofman_2.html
quote: A map from http://freepages.genealogy.rootsweb.ancestr.../...oChart.htm
So Australian Aboriginals would be a check on this hypothesis, as with a similar genetic age and environment, they too should be among those with less visible hair. Not very hairy chested, but lots of male facial hair, and the males have more visible back hair.NCBI Overall more visible male hair than Asians? In modern humans facial hair seems to be sex linked, so the retention of facial hair in males would mean these are the areas not subject to cross-over of selection for less visible hair in females. 2008 | Mathilda's Anthropology Blog. | Page 21
quote:(bold in the original) See J1J2 in N.Africa on the map above for Asian back migration. Also see the link between East Africa CR and Australian Aboriginal C. Unfortunately I can't tell what group(s) would the the Khoisan. And at the end of the day, there is still sexual dimorphism in these groups, and men have hair where women don't, even if it is only facial hair, and they still show more variation in degree of hair visibility.
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 couldn’t possibly have been the primal cause, because early Homo sapiens were not sexually dimorphic in terms of body hair patterns. They also would not have the benefit of further selection in the original ecology for other mutations causing less visible hair, especially where it becomes more critical to survival -- remember one of the markers of run-away sexual selection is that it drives the selection trait to an extreme condition: it is not possible for females to gain less visible hair without actual loss of hair follicles. So I don't think your conclusion is valid: there is still sexual hair dimorphism in these populations, and there is no question of sexual selection today. Thus on one hand we have an existing selection pattern and an overall result consistent with it, on the other you have some other unknown selection process, but still have sexual selection today. And you still have the problem of timing, to derive apparent bareness, the growth of subcutaneous fat and the derivation of sweating from ecrine glands, in a logical pattern consistent with the fossil record and the paleo-climates. Enjoy. Edited by RAZD, : stiles problem Edited by RAZD, : clrty Edited by RAZD, : tibet again Edited by RAZD, : rev 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) • • •
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cervical Junior Member (Idle past 5136 days) Posts: 2 From: United States Joined: |
Im new here, and i havn't read this entire thread. I hope i'm not barging in...
There are obvious reasons for hair in nature. Is there a reason for hair when you have established a means of creating shelter? What if we lost our hair simply because the hairyness no longer gave an advantage? Im no expert in evolution, but traits that offer no advantage get lost in the gene pool.
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RAZD Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi cervical, and welcome to the fray.
There are obvious reasons for hair in nature. Is there a reason for hair when you have established a means of creating shelter? What if we lost our hair simply because the hairyness no longer gave an advantage? There are lots of animals that build shelters to increase their survival ability, so this would not be a new thing, however one should consider the timing of the hair loss to the ability to build shelters and the needs for shelter at the time (and climate) where the individuals lived. There is also the issue of clothes and pests. http://www.newscientist.com/article/dn3807
quote: Clothes, however, would also provide an environment for pests, and there is still the massive (more than on any other ape) head hair to provide continued opportunity for the parasites. My personal opinion is that it was due to sexual selection, selection which is also evident in neoteny and long head hair (think long tail feathers for a similar selection feature). I also believe (again personal opinion) that it was well underway before man ventured onto the Savannah, as we see similar patterns of bareness in Gorillas and in Chimps, just to a lesser degree, but this indicates bareness was an existing feature in the common ancestor ape population. We also share a distribution of ecrine glands on the chest that other apes do not have. In chimps and gorillas these glands keep the bare skin areas moist and supple, and it is these glands that became the sweat glands in humans. The climate in the woodland forest ecology before the Savannah was temperate and buffered from day\night variations by the forest, thus this would enable apparent bareness without endangering survival, something the Savannah cannot do. Enjoy. 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) • • •
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arrogantape Member (Idle past 4662 days) Posts: 87 Joined: |
The new Scientific American issue has a story of h Floresiensis. The idea it is closely related to Homo Habilis has taken root. The similarities are significant. Size, brain capacity, tool making, and morphology link the two.
It seems non plausible to me that scientists staring at the Hobbit's feet don't entertain at least a fleeting thought the feet are great for water propulsion. Michael phelps had large feet, short legs, and a long powerful torso. The Hobbit is built the same, but with a downward curve of the clavicle, giving the hobbit a streamlined neck to shoulder shape. Interestingly, the artist who created the model for the Hobbit pictured in Scientific American made her buck naked. There needs to be an intensive search of shoreline caves in Africa, the middle east, all the way to Indonesia. I think it very unlikely H habilis, or H floresiensis will be found inland. They would stick to the coast, where the geology is fast changing. It's a tall order. I think islands will afford the best places to look.
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Hyroglyphx Inactive Member |
It seems non plausible to me that scientists staring at the Hobbit's feet don't entertain at least a fleeting thought the feet are great for water propulsion. Michael phelps had large feet, short legs, and a long powerful torso. The Hobbit is built the same, but with a downward curve of the clavicle, giving the hobbit a streamlined neck to shoulder shape. Exercise cannot be genetically imparted to the progeny, so it is irrelevant. That large feet incidentally may have helped its survivability is something to look at, but it obviously didn't help the little Ebu Gogo enough. "Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passions, they cannot alter the state of facts and evidence." --John Adams
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arrogantape Member (Idle past 4662 days) Posts: 87 Joined: |
Thanks for the reply. My point being that the unusual morphology of Phelps is behind his success. Long arms, long torso, short legs, long feet are great gear for swimming. The little hobbit lasted for a 100 thousand years in just that one cave. H habilis was a long survivor. The Hobbit is almost certainly derived from H Habilis, or the other way around. Whatever the genealogy hierarchy, The little guy did not swim to Flores from Africa. It was a slow procession along the shores by thousands of ancestors, beach by beach. My bet is they will never find this hominid again. Flores was unnatural as it had no large predators. That allowed the diminutive clumsy Hobbit to venture inland and establish a home there. Only on like no predator islands where you might find a cave with remains. Lets hope they do.
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RAZD Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Let's put one of your wild assertions to bed, arrogant ape:
Flores was unnatural as it had no large predators. Flores - Wikipedia
quote: Komodo Dragons are scavanger predators, fully capable of taking down full sized humans, they can be fast, and they are dangerous ambush predators. Komodo dragon - Wikipedia
quote: So they were on the island before H.floresiensis. There is also some evidence that humans (including H.erectus aka Javaman) also used the lowered sea level to walk to many places that are now islands. Enjoy. 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) • • •
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adelpit346 Junior Member (Idle past 5120 days) Posts: 11 Joined: |
Spam
Edited by AdminSlev, : No reason given.
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RAZD Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Exchange with Mr Jack from Message 49 to Message 52 on Is body hair a functionless vestige? moved here:
quote: Mr Jack Message 49 (2) IF this were true THEN the most hairless appearing humans would be the hunters and not the gatherers. Conclusion: women did the hunting while the men did the gathering. Please compare this to what you know about anthropology. African men are considerably more hairless than european men. It is quite plausible that the increased hairiness of men in Europe represents a trend of adaptation to colder conditions.
quote: Those aren't persistance hunters. Humans are the only species in the world known to persistant hunt, AFAIK.
quote: Using recent, predominantly western european fashions as evidence for long term evolutionary trends strikes me as absurd in the extreme. quote: Mr Jack Message 52 Riiight, I wouldn't dream of claiming that the present is the key to the past, and that, just because something is existing today, that it could have been existing in the past. ...yes? Sure, but using something we know has changed within the last hundred years and isn't culturally uniform as the basis for an argument is profoundly flawed. I am not aware that the sexual dimorphism in hair patterns has changed in the last ~4000 years of recorded history, nor that archeological studies of early Homo sapiens artifacts show any reference to different hair patterns. Again, the real issue is not so much explaining an apparent bareness of human beings, but to explain the sexual dimorphism that is evident between males and females. Another discriminate characteristic of humans compared to apes is the neoteny evident in humans, particularly in femalse. Neoteny - Wikipedia
quote: This would suggest that the selection for vellus hair in women is part of the neoteny selection for young appearing females. Sexual selection - Wikipedia
quote: Which explains why the hairiness in men is highly variable, while the apparent bareness of females is very consistent. Enjoy. Edited by RAZD, : spling 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) • • •
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.4 |
I agree that the dimorphism between the sexes is down to sexual selection. Or, at least, it is involved in sexual signalling. The large beard of males probably serves a similar function to a Lion's mane.
I'm unconvinced by the argument that hairlessness* of humans represents sexual selection. What I really don't buy is your argument-from-recent-porn. * - Yes, technically we're not hairless. You know what I mean.
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.4 |
This would suggest that the selection for vellus hair in women is part of the neoteny selection for young appearing females. Humans, male and female, are not neotenous. We have numerous paedomorphic traits (acquired at different points in our evolution) but the relative paedomorphy of traits reflects differing selective pressures through human evolution not a neotony event.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Humans, male and female, are not neotenous. We have numerous paedomorphic traits (acquired at different points in our evolution) but the relative paedomorphy of traits reflects differing selective pressures through human evolution not a neotony event. This is a fine distinction; and I'm not convinced by your selectionism. It is at least plausible that (hormonal?) changes favored because they produced one selectively advantageous pedomorphic trait could as a side-effect have induced another which was neutral or even somewhat disadvantageous.
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.4 |
This is a fine distinction; and I'm not convinced by your selectionism. It is at least plausible that (hormonal?) changes favored because they produced one selectively advantageous pedomorphic trait could as a side-effect have induced another which was neutral or even somewhat disadvantageous. It is plausible for that to happen, yes, almost all genes have multiple effects. However, the differing timing of the various paedomorphic traits means that there has been no overall neotony of the human form but rather multiple incidences of paedomorphy. Hairlessness could be non-adaptive, but I find it unlikely. If hairlessness was a neutral trait we'd expect it to be more randomly distributed through populations.
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Dr Adequate Member (Idle past 305 days) Posts: 16113 Joined: |
Hairlessness could be non-adaptive, but I find it unlikely. If hairlessness was a neutral trait we'd expect it to be more randomly distributed through populations. Not neceassarily. Consider the possibilities that (a) it was a side-effect of an adaptation for a non-neutral trait, which is what I suggested; or (b) it got fixed at some time before the human population was small and undispersed.
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RAZD Member (Idle past 1426 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi Mr Jack, sorry to take so long getting back to you.
I agree that the dimorphism between the sexes is down to sexual selection. Or, at least, it is involved in sexual signalling. The large beard of males probably serves a similar function to a Lion's mane. Or the different facial hair patterns seen in males of many species of primates.
I'm unconvinced by the argument that hairlessness* of humans represents sexual selection. What I really don't buy is your argument-from-recent-porn. * - Yes, technically we're not hairless. You know what I mean. Curiously, being unconvinced does not imply that it is not true, just that you have trouble accepting it based on the information available. And it isn't an "argument-from-recent-porn" that I am making. What I've said is that IF this pattern of sexual selection still exists, that we should see evidence of it. Particularly, if it is due to runaway Fisherian sexual selection, we should see evidence that goes beyond what is possible. These studies have been done on facial characteristics for female beauty, with the result that an unreachable childlike appearance is found more desirable than what is genetically possible at this time. Apparent bareness also fits this model, not just in modern porn but also in a whole industry devoted to hair removal: Hair - Wikipedia
quote: Again I refer you to the "Venus" razor ads. And to documentation that "male hair pattern" in women is considered an undesirable medical condition. It's multiple lines of evidence pointing in the same direction.
Message 94 Humans, male and female, are not neotenous. We have numerous paedomorphic traits (acquired at different points in our evolution) but the relative paedomorphy of traits reflects differing selective pressures through human evolution not a neotony event. Neoteny\paedomorphy\tomatoe quibble. Meaning is the same in the end. So you are claiming a number of discrete events while I am considering an overall long term trend that takes advantage of various mutations along the way, due to Fisherian runaway sexual selection that brings us to modern humans from ancestral apes. If what is being selected are juvenile features in women capable of reproduction, then we should see a number of juvenile features in a state of arrested development when compared to other apes, and when compared to males. Vellus hair is a juvenile feature.
This is the current average sexual dimorphism in humans, where the shaded areas are where androgenic (or terminal) hair grows. The bare portions are where vellus (or juvenile) hair grows. Then there is the issue of blond hair ... ... and this
Enjoy. Edited by RAZD, : added last image 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) • • •
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