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Author Topic:   Is body hair a functionless vestige?
Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 60 of 143 (565552)
06-17-2010 8:28 PM
Reply to: Message 59 by Artemis Entreri
06-16-2010 6:24 PM


Re: Anyone disagree that body hair has sensory function?
Artemis Entreri - Sorry, but my hairs are able to sense things at a threshold much lower than my bare skin. I don't believe I am unusual in this respect. I've described simple experiments that show this to be the case - a hair too fine to feel brushed across skin but can be felt by body hairs is hardly brute force. Yes, the nerves involved are within the skin and almost certainly include the feedback of erector pilori muscles. By the physics of levers even small forces can move a fine hair enough to be sensed. Clearly there is a threshold - that a speck of dust is below.

For detection of insects and ticks I have no choice, given my own everyday experiences, to conclude that vellus hairs are superior to hairless skin - and very fine vellus hairs are superior to thick heavy hairs - for detection of very small stimuli. Try brushing the very fine hairs high over cheekbones or on your nose or ears; in my case its an effort to not have the irritating tickling cause me to rub or scratch. I think the tactile sensations of skin and hairs tend to merge in our perception and I suggest you may be attributing most of what you perceive to direct skin touch rather than to the movements and vibrations of hairs. The sensations are subtly different and by paying close attention it is possible to learn to discriminate between them. The sensory function of hair insignificant? I don't think so.


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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 65 of 143 (565730)
06-19-2010 8:48 PM
Reply to: Message 61 by Blue Jay
06-18-2010 12:22 AM


No-one here says body hair is functionless?
Bluejay - you said...
"I’m not sure why you think any of us would be arguing that hair is non-functional."
Perhaps not the people here but it is a widespread meme. Try googling 'useless body parts' and you'll find source after source that includes body hair in the list. Including some that I would have considered reliable. Erector pilori muscles and goosebumps often appear there too, and, since those muscles hold hairs erect during moments of fright and hairs do have sensory function I'm also arguing that goosebumps have a related function by extending touch sensitivity to the furthest distance from the skin.

What I have encountered here is resistance to the idea that body hair, even with acknowledged sensory function, actually provides any significant benefits from this function. A lot seems to depend on the sensitivity; I maintain that hairs provide sensitivity greater than hairless skin as well as do it beyond the surface of the skin and that it has - more than once - enabled me to remove toxic parasites before they could dig in to my flesh. Some here seem convinced that I would have felt those ticks anyway - by direct skin contact. I've watched flies landing on my feet and not felt them until and unless they ventured into the hairy areas so I have to disagree. So, to me it seems obvious that hairs provide a sensitivity to touch that bare skin doesn't. I spend a lot of time outdoors, in a rural environment, where such sensitivity does still retain some usefulness. Without some rigorous, independent experimental evidence that disagreement seems unlikely to be settled here.

Now, the argument that such a function was not directly relevant to the evolution of the modern state of human body hair could have merit - I make no claim to deep knowledge on evolution - but I'm still doubtful that such a - to my mind - useful function could have been irrelevant, if only as cause for retention of what's left. Whether such sensitivity has undergone evolutionary changes is speculative; what isn't is that a thick pelage, with hairs all up against each other, would dampen small movements from further along the hair shafts and tend to reduce sensitivity to low threshold impulses. So in that sense I think that smaller, more widely spaced hairs would indeed provide greater sensitivity than the hairs of a thick pelage.

My opinions regarding thermoregulatory function aren't so strongly held although I think the argument that the change from thick pelage to thin benefits cooling from perspiration seems sound. The part the remaining hair plays seems less clear.


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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 66 of 143 (565733)
06-19-2010 9:16 PM
Reply to: Message 63 by Taq
06-18-2010 10:35 AM


Re: Anyone disagree that body hair has sensory function?
If, after evolution has reduced or taken away the primary function of a body part, it retains other functions, wouldn't one of those functions then become it's current primary function? Nitpicking? (ha, couldn't resist).
Yes, hair can hide ticks and other parasites. It can also alert us to their presence. In an age of pesticides and high fashion this may be counted as useless, except lots of people still lack ready access to either and could still find it useful to detect ticks prior to being bitten. When it really matters we can pay a lot closer attention to such somatic sensory information; I think the greatest limitation to such a sense is lack of attention and awareness so many people give it.

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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 69 of 143 (581030)
09-13-2010 3:35 AM
Reply to: Message 68 by greyseal
09-12-2010 1:35 PM


Gradual or rapid change to our hairiness
Greyseal, you said "I don't think it's been fur for a while, but we gradually lost that hair. " I'm curious to know why you think it would have been gradual; if it was the result of a mutation reduced hairiness would have appeared in an individual, apparently out of nowhere. That it is a trait that is strong through childhood until puberty suggests to me that the fundamental 'furless' trait is independent of sexual dimorphism - the male/female differences in adulhood - that is probably a result of sexual selection.

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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


(1)
Message 71 of 143 (581128)
09-13-2010 10:15 PM
Reply to: Message 70 by greyseal
09-13-2010 5:34 AM


Re: Gradual or rapid change to our hairiness
Greyseal, I think that, if a single furless mutant successfully reproduces and has furless descendents the trait could be established within a sub-group. It doesn't have to have provided any net benefit and could even have been an initial disadvantage, so long as it was not so disadvantageous that it prevented reproductive success. Of course if it did confer advantage that makes it more likely they would demonstrate fitness (as in fitness = reproductive success). I don't see why it takes more than one to start things off; the question then becomes why the fully furred lines failed whilst the furless ones succeeded.
There are multiple ways an ugly furless mutant could go on to breed successfully especially if being thin furred confers benefits, such as better health through reduced ecto-parasite loads or better stamina and hunting success through better heat dissipation. Just having greater determination and more aggression could be enough to push more attractive rivals aside to mate successfully; being different can in itself be an incentive to try harder. Or it could be just pure luck and circumstance; the fully furred dominant males fail to return from a hunt and the barely tolerated ugly hairless one got an unexpected opportunity. I think it's a mistake to underestimate the part pure chance would have played within a very small and vulnerable foundation population.

Edited by Ken Fabos, : added a paragraph


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 Message 72 by greyseal, posted 09-16-2010 7:49 AM Ken Fabos has replied

  
Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 73 of 143 (581672)
09-16-2010 9:10 PM
Reply to: Message 72 by greyseal
09-16-2010 7:49 AM


Re: Gradual or rapid change to our hairiness
Greyseal, I am engaged in speculation and don't insist this was how it must have happened. I've been thinking about how the underlying genetics can become widespread prior to the trait revealing itself in a major way. Yes, a strong characteristic like this would not have to come about as a dominant trait passed directly to furless descendants (although I still think it could be possible).

I still think that mutations must come from single progenitors - but there may not be outward manifestation of it until the mutant gene is widespread enough to recombine with itself. Within a small population that may not be that many generations. Mutations will go on to be 'fixed' within the gene pool when enough members of the population carry it; those will all be descendants of that original mutant individual. Over enough generations it will become a case of interbreeding between members who had that progenitor; that's true of any species after enough generations.

I don't understand the processes well enough, but as I understand it some traits require the same allele to come from both parents - or for different alleles from different evolutionary lines that complement each other to combine to produce a trait. Yet that could still result in a strong change seemingly appearing out of nowhere rather than as a gradual loss of fur. Although it's occurence would be rare at first and seem confined to siblings, it could appear separately amongst groups who would not seem to be closely related.

I'm just not convinced it's purely natural selection at work. Natural selection works with what's already in the gene pool and, without some form of mutation, won't come up with new genetics. Can natural selection be responsible for such a strong divergence? Being fully furred from early childhood - as our closest ape relatives exhibit - seems fundamental; such a big change to that just seems unlikely without some serious genetic change. I really don't know, but our thinned pelage is such a strong and universal characteristic of our species through childhood until puberty that I have doubts that what we have now is purely a result of natural selection. The variations in our adult pelage on the other hand looks more likely to be a result of a subset of natural selection - sexual selection - but to me that looks to be independent of the fundamental furless trait as exhibited through childhood.


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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 75 of 143 (582374)
09-21-2010 12:36 AM
Reply to: Message 74 by greyseal
09-20-2010 7:21 AM


Re: Gradual or rapid change to our hairiness
Greyseal - I don't see how mutations can derive from anything except individuals - whilst a specific mutation can occur independently the chances of that aren't high wheras a mutant gene will be passed to descendents and, as long as that line doesn’t die out, will almost certainly become part of the gene pool.

From Introduction to Evolutionary Biology - by Chris Colby - "Substitution is the replacement of an allele by another in a population. This is a two step process: First a mutation occurs in an individual, creating a new allele. This allele subsequently increases in frequency to fixation in the population." Whist allele substitution is one of several forms of mutation the idea that it derives from individuals seems implicit within Colby's writing on it. So I think you will find that I'm correct that mutations arise in individuals and a mutation becomes more common within the gene pool with successive generations through being passed on to direct descendents. For relatively small and isolated groups of proto humans there's no reason to believe very close relatives were necessarily prevented from mating and even if direct incest (parent and offspring or between siblings) was not practiced it doesn’t take many generations before a small population shares common ancestors. Also what is beneficial, neutral or deleterious could be skewed by possession of intelligence and ability to use tools; the ability to change behaviour to overcome physical limitations looks to be a long standing trait of our lineage.

Whilst natural selection is the way adaptation happens it is selection between existing variants; (Colby - "The opportunity for natural selection to operate does not induce genetic variation to appear -- selection only distinguishes between existing variants.") Ongoing evolution depends upon genetic variation which ultimately comes from mechanisms other than natural selection of which mutation is the most fundamental. ( "In order for continuing evolution there must be mechanisms to increase or create genetic variation and mechanisms to decrease it. Mutation is a change in a gene. These changes are the source of new genetic variation. Natural selection operates on this variation.")

I find it unlikely that the kind of reduction of fur (that's so strong that it pervades our species but not our nearest relatives) could get that way purely by natural selection from within a fully furred population without some kind of mutation - was our proto human hairiness that variable? Surely we are talking relatively small numbers within a not very fecund species with long maturation times. Whilst mutation would be rare, it would be more likely - so long as not seriously deleterious - to be passed on and become fixed within the gene pool.
Complex traits don't tend to be about genes in isolation, yet a gene that changes the way hair growth responds to biochemical signals during growth maybe could be down to small genetic changes. Note that I said unlikely it's all natural selection; I'd actually like to discuss this with people with a strong grounding in evolutionary biology and the evolution of hair. But most of all I still want to know why the clearest remaining physical function of body hair - it's sensory function - seems to be entirely absent when it comes to understanding how we ended up with a pelage the way it actually is. Isn't the point to understand how we got to be the way we actually are? Evolutionary anthropologists like M.Rantala and N.Jablonski have not, so far as I can discern, correctly identified this function of body hair and seem to discuss body hair like it is vestigial and has no real function. Given how wrong that is how can their speculations on it's evolution be considered to have a sound foundation?


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Replies to this message:
 Message 76 by greyseal, posted 09-23-2010 6:05 AM Ken Fabos has replied

  
Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 77 of 143 (583534)
09-27-2010 8:50 PM
Reply to: Message 76 by greyseal
09-23-2010 6:05 AM


Re: Gradual or rapid change to our hairiness
Greyseal - whilst I don't fully understand evolutionary processes, I don't think you do either although I have to say thanks for making me think about this more deeply than I otherwise might have.

To start, the offspring of parents aren't mutations even though they aren't exact copies; the differences would be a result of recombination not mutation. Just what role recombination plays in producing traits that have not existed previously is something I admit to not fully understanding but mutation is when genes replicate with ‘mistakes’. These mistakes are random and won’t appear in response to environmental or other factors, just get carried, replicated or lost according to the fitness (reproductive success) of the random individuals that carry them. Past the initial occurance they probably shouldn’t be called mutations but the changed gene in later generations seems to be called that for the sake of convenience.

My understanding (mostly from Colby’s Introduction to Evolutionary Biology ) is that, whilst the same mutation can occur independently, it's an extremely low probability random event. This fits with my own thinking about the size of a genome and the random nature of mutations. The same beneficial (or at least not seriously deleterious) mutation occurring independently across a larger population is very unlikely. Should similar traits arise out of different genetic changes, I doubt they would be carried universally or breed true. Having a mutation arise in an individual, be inherited by descendents and spread through the gene pool through successive generations looks both reasonable and much more likely than arising independently. As Colby concisely puts it - genes mutate, individuals are selected and populations evolve. I can only refer back to Colby's online article which refers to mutations several times as occuring first within individuals. I can only believe he does correctly summarise evolutionary processes; natural selection selects between existing traits, those traits arose from mutations in individuals and were spread through following generations by inheritance. He refers to the equation 4*N for the number of generations for a mutation to reach fixation, where N is the effective breeding population. For a small tribe of proto humans (below 100), that rarely mate outside it that would be in the hundreds generations – multiplied by 20 years per generation ( which is probably overgenerous) we’re talking around 100,000 years or less. That is the time before that population all had that common ancestor. This would be even faster when mating choices aren’t random as that would reduce the effective breeding population that carry that changed gene – and for homo sapiens we know that mating options are ‘assortative’ as in we tend to mate with people like us. Less hairy with less hairy? That would lead to a sub-sub- population with that trait. If it’s associated with greater fitness (reproductive success) the relative numbers of furry to furless would shift in favor of the latter.

I think that traits that are common to our entire species have to predate it's major diaspora and even if some traits could have developed independently within reproductively isolated sub-groups, having them develop within all sub-groups would be so unlikely as to be effectively impossible. So I believe that furlessness predated our species spreading far and wide.

You said - "unless they were immediately bald like us, chances are there will be further mutations reducing hairiness, which would again confer better survivability, which would once again mean that more and more of the population (over time) has this new-new gene change." I suppose that could occur except that I think 'further mutations reducing hairiness' would not be likely; all mutation is random and beneficial mutations rarer than neutral to deleterious ones. Chances are the appropriate mutations will not happen when or because it’s needed. I suppose that would lead to slow development of this trait, but would an incremental change to hairiness really provide better survivability or reproductive success?

I have to admit that how far natural selection can take a trend such as toward reduced hairiness is a valid question and I’m still uncertain about it; selection of the least hairy from each generation might continue that trend further than I might initially expect. But that depends on that trait providing clear advantage - or more strictly speaking having natural selection favour the reproductive success of those with less hair over those that don't. What I don’t think is clear is that incremental changes to reduced hairiness would have enough benefit, generation to generation, to give greater reproductive success; heat dissipation – the most established advantage that is claimed for reduced hairiness - is a result of two significant changes; more watery and abundant sweat as well as reduced hairiness. (Tougher skin is also a related trait that humans appear to possess, but I don’t want to complicate this too much). Each trait by itself may not have conferred great advantage and it was when the two combined that this gave significantly better heat dissipation, thus greater endurance in hot conditions and consequently gave those with them superior hunting and gathering range and ability. When the benefits of changes to hairiness without change to sweatiness are pared down even further by occurring as small incremental ones they are even less likely to result in selection in favour of them. Gene flow - mixing of previously separate gene pools - would, if these separate traits evolved within separate groups, result in less fur and more watery sweat being combined and again that clear advantage would first appear in individuals and siblings, not across the population over a long time. But prior to more abundant perspiration the impacts of thinned fur, even if arising rapidly, may have been marginal or even detrimental if severe cold, was still a limiting factor. Similarly, had greater perspiration come first there may have been disadvantages since greater water loss without much better heat dissipation would have limited, not extended, their range for hunting and foraging.

Reduced parasite loads from thinned fur also has it's complications - thick fur can protect against some kinds (e.g. mosquitos and small biting flies) whilst providing better habitat for others (lice or fly maggots in wet matted fur) or change how easy they are to locate and remove (ticks). Also the disease carrying aspects can make specific parasites more and less significant; as long as mosquitos don’t carry disease we can tolerate more of them but when they do –and the disease is serious – that can heavily impact a population and do so quickly. So, by having more of the body more easily scrutinised visually, some parasites are made easier to physically remove whilst we could be more vulnerable to others. Still, shorter thinner hair's finer sensitivity to low threshold tactile sensation gives greater sensory awareness of the presence of some kinds of parasites, so, depending on which parasites and diseases, being thin furred could have mattered greatly to the health and consequently the reproductive success of the individuals who became the foundation parents of our species. Insects are well known for being able to adapt quite quickly so slow, incremental changes in our ancestors may not confer much advantage given that parasites can adapt quickly enough to keep up. In this respect rapid change could confer more advantage than incremental change to hairiness. So we get back to luck and chance.

Chance as it effects individuals (individuals are selected both by the relative advantage and disadvantage of the traits they carry as well as by life's chances) would play an important part. A beneficial mutation that might go on to have enormous advantage could easily be lost if the initial individual carrying it meets random misfortune. Harmful mutations, at least the most serious ones, by their nature, tend to die out and not get passed on. And those are still more common than mildly deleterious through to beneficial mutations. That's why I see chance and luck in both the right mutations arising and the individuals with them surviving as playing a crucial role in us being the way we are.

PS I wonder if some of this discussion has relevance to The common ancestor thread? I've been a bit busy to get involved in it.


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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 78 of 143 (588768)
10-28-2010 7:20 AM


Sensory function of hairs predates insulation?
I recall reading - just a reference in comments on another forum but unfortunately can't find it again - to speculation that the earliest function of hair was sensory. It seems to be a universal characteristic of hairs to transfer tactile impulses to sensory nerves within the skin. Presumably hairs existed before their role as insulation; did they transmit tactile impulses before then? Did they have muscles to hold them erect? Goosebumps may have had the role of extending the reach of tactile hairs long before they acquired the role of signaling to predators. It would mean that they are not vestigial, as they still perform this function.

(Edit p.s. - Since found the reference to this article - http://onlinelibrary.wiley.com/...1600-0625.2003.00069.x/pdf although it doesn't really explore sensory function prior to (or during or after) hair/fur as insulation, rather sees a mechanoreceptor role as an early intermediary step to hair as we recognise it. It looks like the author is one more academic of evolution of hair that fails to recognise the near universal tactile sensory function of hairs. That seems implicit in this sentence... "Later, as endothermy was gradually perfected in early mammals, perhaps a Jurassic event when they occupied the nocturnal niche (11), an insulatory boundary was further improved by multiplication of nontactile hairs." ... which I take as differentiating hairs that are clearly specialised for tactile function - such as Vibrissae hair (whiskers) - from those that aren't. One more who should know better that has failed to notice that even the non-specialised ones retain a tactile sensory function.)

Edited by Ken Fabos, : Added p.s.


  
Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 92 of 143 (611662)
04-09-2011 6:47 PM
Reply to: Message 80 by Robert Byers
04-08-2011 3:40 AM


Robert, a bit of speculation is fine but I'm not impressed so far. If patterns of hair growth respond to wetness of climates we'd see such patterns in geographic distributions. We don't. That hair has some capability to wick water away from the skin has some basis but an innate ability for hair patterns to 'respond' hasn't been shown; I believe that our characteristics evolved but the specifics of how we came to have the hair functions and patterns we do has not been (may never be) clearly explained. To what extent it's chance and how much it's adaptation interests me - I happen to think our body hair function very well as part of our tactile sensory system and extreme sensitivity of fine hairs around eyes and ears suggest some degree of adaptation. I don't mind indulging in a bit of speculation about it, but I don't think this response to wetness idea, as presented, is anything that throws any light on it.

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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 100 of 143 (612023)
04-12-2011 6:11 PM
Reply to: Message 95 by Robert Byers
04-12-2011 1:22 AM


"...What is the hair doing!"
It demonstrably does have a sensory function. It does other things too, including (in places) wick moisture away from the skin, protect from UV exposure and provide insulation but it definitely does tactile sensitivity as well and it does it extremely well. All hairs have this capability but around eyes and ears the sensitivity is notable (leaving aside eyelashes which I'd say are clearly an extreme adaptation for tactile sensitivity) - the nearly invisibly fine vellus hairs on skin around these vital organs alert us to the presence of very small insects by their sensitivity - my own experience is the resulting sensations are so strong it takes a conscious effort not to rub or scratch. I'd say that this is a useful function and, around eyes and ears, a far more useful function than the ability to wick away water.

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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 132 of 143 (613348)
04-24-2011 7:58 PM
Reply to: Message 131 by Robert Byers
04-21-2011 10:20 PM


This hypothetical ability to quickly adapt to wetness - very quickly if the entire history of homo sapiens is a few thousand years - would cause strong and clear variations according to geography and climate within human sub populations. We don't see that. Such an 'oversensitive' adaptive ability that simply stops or gets 'stuck in the gear' isn't a real explanation for why we don't.

Sorry but this transient adaptive ability of hair to respond (before getting stuck in gear) to wetness is pure conjecture without basis in evidence.

Women more hairy than men? I think that perception is more about modern social rituals involving scissors and razors than innate physiological differences between men and women; take away those rituals and men are more hairy than women, if not in all the same places - similar density of head hair plus extra on face and rest of body.

As for insulation being the primary function of hair I'd have to disagree; the sensory function is a more fundamental function of hair and (as I pointed out before) looks to predate hair/fur as insulation - right back to the precursors of mammals. Colour, thickness, distribution and growth patterns are all highly variable but the ability to pass tactile sensory signals to receptors in the follicles and surrounding skin looks to be a universal characteristic of hairs that has never been lost.

I think YEC's should stick with 'because God made it that way' and not bother with attempts to sound sciency.

Edited by Adminnemooseus, : Blank lines.


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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 138 of 143 (644307)
12-17-2011 2:42 AM


Does this vindicate my arguments?
Check out this article about a recent publication in Biology letters about the role of hairs mechano-sensory function with respect to ectoparasites. Why it's taken so long for anyone to notice that the sensory function is both real and useful - and give it genuine consideration when exploring human evolution is as much a mystery to me as them questions of how our 'hairlessness' evolved.

Edited by Ken Fabos, : fix link

Edited by Ken Fabos, : No reason given.


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 Message 139 by Granny Magda, posted 12-17-2011 8:16 AM Ken Fabos has replied

  
Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 140 of 143 (644393)
12-17-2011 1:59 PM
Reply to: Message 139 by Granny Magda
12-17-2011 8:16 AM


Re: Does this vindicate my arguments?
Granny Magda @139, people here also disputed that hairs even have a sensory function. That's something nobody should even need to have pointed out! Doesn't theirs work or something?

Meanwhile Nina Jablonski in Sci-Am listed known functions of human hair but left out what is, for fine vellus hair, it's most distinct and clear function - sensory.

You will find that this article explores the idea that the mechano-sensory function of hairs probably predates it's function as thermal insulation and even predates the forms that we think of as mammals. ie it's not vestigial but may be the original function; it still has that function and it may still be continuing to be it's primary function.

I think it's a universal function and mammal hairs that have lost their sensory capability would be a rare exception. But if no-one asks the question how do we know the answer?

A bit combative aren't you? Not that it upsets me - these forum often are. I found this one an interesting debate that stimulated my thinking. And I don't claim great expertise, just an occasional ability to point out the obvious when all around me no-one appears to be noticing it.

The sensory function of body hairs ought to be obvious to everyone and I'm still very dismayed that leading scholars in this field appear not to have even acknowledged - until well after this thread began - that it has any relevance to the evolution of our misleadingly named 'hairlessness'.


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Ken Fabos
Member (Idle past 553 days)
Posts: 51
From: Australia
Joined: 05-09-2010


Message 142 of 143 (646195)
01-03-2012 4:00 PM
Reply to: Message 141 by Robert Byers
12-30-2011 1:19 AM


Re: Does this vindicate my arguments?
Robert, the papers I've linked to suggest that sensory function is a fundamental function of hair and probably preceded it's function for keeping warm in mammal evolution. Temperature regulation via fur may have become very crucial for most mammals but the sensory function remains.

For something like eyelashes it's directly linked to the blinking reflex and protecting eyesight is important for most mammals. That the fine vellus hairs on my own face near to my eyes are so touch sensitive that it's all I can do to not rub or scratch when they are disturbed suggests a long and continuing evolutionary history that involves the mechano-sensory function. The paper by Dean and Siva-Jothy shows what I have suggested - a mechanism by which natural selection would favour finer, sparser body hair.

Meanwhile your 'after the biblical flood' scenario isn't an explanation that works for anything except, via a roundabout and convoluted route, to support a scientifically unsupportable position.


This message is a reply to:
 Message 141 by Robert Byers, posted 12-30-2011 1:19 AM Robert Byers has replied

Replies to this message:
 Message 143 by Robert Byers, posted 01-03-2012 9:25 PM Ken Fabos has not replied

  
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