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Author Topic:   why is the lack of "fur" positive Progression for humans?
Coragyps
Member (Idle past 734 days)
Posts: 5553
From: Snyder, Texas, USA
Joined: 11-12-2002


Message 16 of 27 (449716)
01-18-2008 8:29 PM
Reply to: Message 12 by dwise1
01-18-2008 7:50 PM


Remember, the horse may be faster over a shorter distance, but can the horse keep up its pace for longer than a man could? That is the real question.
I've read, long, long ago, that humans (myself certainly excluded) can beat a horse in a marathon (26 mile) race.

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molbiogirl
Member (Idle past 2641 days)
Posts: 1909
From: MO
Joined: 06-06-2007


Message 17 of 27 (449722)
01-18-2008 8:35 PM
Reply to: Message 10 by RAZD
01-18-2008 7:40 PM


This is either another example of neoteny in humans or it is the raison d'etre for neoteny (ie sexual selection for younger appearing females).
According to this guy ...
Evolution of nakedness in Homo sapiens
Journal of Zoology 273 (1), 1-7.
... there are a couple of problems with neoteny.
It has been suggested that humans are a juvenilized form of ape (Gould, 1977). ... If the hairlessness of the foetal ape was being retained into adulthood by a process of neoteny, one would expect the human body to retain this characteristic throughout its whole development from embryo to adult. However, this is not the case. When the human foetus is 6 months old, it becomes completely covered with a coat of fine hair known as lanugo. Normally, this hair is shed long before birth; occasionally, a baby is born still wearing its woolly coat, only to lose it within the first days after birth (Morgan, 1982).
Another weakness of the theory is that while some characteristics may be retained as part of a neotenic package, this only applies to characteristics that are either benign or neutral in their effect on fitness to survive. No one claims that all foetal characteristics are retained in a neotenic species. For example, a human foetus and a human baby both have very short bandy legs, but natural selection ensures that this feature is not retained in adult life (Morgan, 1990). Furthermore, the neoteny theory does not tell us anything about the value of nudity as a new character that helped the naked ape to survive better in his hostile environment (Morris, 1967).
Ditto for sexual selection.
Furthermore, expensive sexual signal for the purposes of sexual selection are usually seasonal, and generally develop after sexual maturation. Although H. sapiens males are generally considered to prefer less hairy females (Darwin, 1871), and sexual selection may have facilitated the evolution of nakedness (Rantala, 1999; Pagel & Bodmer, 2003), Darwin's hypothesis does not explain what initial selective advantage would have caused males to start to prefer more naked females (see Fisher, 1930; Kokko et al., 2002).
Another author points out that it is unusual in sexual selection to have the same trait selected for in both sexes.
Evolution Theory and Practices
Eviatar Nevo, Solomon Pavlovich Vasser, 2004, p. 334
Although Dawkins seems to think that when one sex evolved "ahead" of the other, the other sex can be "dragged in its wake".
The Ancestor's Tale
Richard Dawkins, 2004, p. 264

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jar
Member (Idle past 393 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 18 of 27 (449723)
01-18-2008 8:40 PM
Reply to: Message 14 by NosyNed
01-18-2008 8:02 PM


Re: Running Farther
But we are talking about survival advantage and fur. Remember that evolution does not look for ultimates, but just good enough. While humans may well be able to run down most prey, particularly using teamwork, there is a converse, being able to out run predators.
It might well have been a happy compromise, but other species such as the hunting dogs, coyotes, wolves and such that do have hair also are known for long range hunts.
While we will likely never know for sure, I believe that the reality is more likely that humans ended up as they did because that was just good enough.

Anyone so limited that they can only spell a word one way is severely handicapped!

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 19 of 27 (449728)
01-18-2008 8:56 PM
Reply to: Message 11 by nator
01-18-2008 7:48 PM


Of course, horses sweat over their entire bodies.
So sweating explains bare appearance in humans how?
This concept of hair - sweat is a tie over from the old "savanna" theory of human bipedalism. Now that we know that bipedalism evolved before the savanna ecology this theory has been discredited.
Now go back and rethink the bareness issue.
Enjoy.

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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
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Message 20 of 27 (449731)
01-18-2008 9:10 PM
Reply to: Message 12 by dwise1
01-18-2008 7:50 PM


Not faster, but farther. Take for example, the cheetah, which is the fastest land animal. In a 100-yard dash, it would beat us hands ... er ... paws-down. But who would win a 1-mile run?
The difference here is the human brain not the fur\bareness. Delayed gratification. The cheetah is the ultimate get-it-now-or-give-up approach, one you will see in many other animals. What makes humans, wolf packs and similar hunting behavior different is backing down from all out running and being able to track the prey. You can walk a deer down.
Remember also that the excess body heat I'm talking about is generated by the act of running. Not just from walking about in the noon-day sun, but from running.
Which again points to the women being the runners then. Half the hair of men.
The fact that there is sexual dimorphism in human hairiness shows you where it is being selected - in the sex with the more pronounced expression of the trait.
Next look at a few porn websites for unnaturally hairy women, naturally hairy women and unnaturally bare women. Look at ads. Look at the ever hair growing market for hair removal products and tell me that there is not ongoing sexual selection for bare appearing women. Why does googling "hairy women" produce websites of naturally hairy women versus ones with unnaturally shaved arms, legs, etc.?
And this has nothing to do with why we are bare. What you may be looking at is the fact that the pre-adaptation for bareness while still in the forest-jungle ecology allowed this ability to develop and not the other way around.
Running does not explain sexual dimorphism. Sex does.
Sex made us human.
Enjoy.

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RAZD
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Posts: 20714
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Message 21 of 27 (449736)
01-18-2008 9:23 PM
Reply to: Message 13 by jar
01-18-2008 7:57 PM


Re: Wolves
Ever see a wolf Pack hunting? Deer running?
It's called cursorial hunting:
quote:
The hunters will pursue at a relatively measured pace a targeted quarry which in response will make short but high energy sprints to escape. Eventually the relentless pursuit will exhaust the quarry allowing it to be brought down by its pursuers.
Wolves, hyenas, lungless spiders and humans are all animals that are well adapted to using this hunting strategy.
None of which needed to evolve bareness to hunt in this manner.
Enjoy.

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RAZD
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Posts: 20714
From: the other end of the sidewalk
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Message 22 of 27 (449737)
01-18-2008 9:25 PM
Reply to: Message 18 by jar
01-18-2008 8:40 PM


Re: Running Farther
But we are talking about survival advantage and fur.
Or the breeding advantage of apparent bareness ... to the point where it threatened survival and clothes had to be invented for it to continue ...
Enjoy.

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we are limited in our ability to understand
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RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ...
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RAZD
Member (Idle past 1404 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 23 of 27 (449740)
01-18-2008 9:30 PM
Reply to: Message 17 by molbiogirl
01-18-2008 8:35 PM


Another author points out that it is unusual in sexual selection to have the same trait selected for in both sexes.
It isn't. It is selected in women, males just inherit it. Look at the variation in males versus women.
Women - nearly all similarly bare, a disease with "male pattern hair" is a dreadful thing requiring treatment, just having a "mustache" is undesirable, trait heavily selected.
Men - from nearly bare to covered in hair, all having little trouble finding mates, trait not selected at all.
Enjoy.

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we are limited in our ability to understand
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RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ...
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This message is a reply to:
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Message 24 of 27 (449742)
01-18-2008 9:38 PM


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jar
Member (Idle past 393 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 25 of 27 (449746)
01-18-2008 9:40 PM
Reply to: Message 22 by RAZD
01-18-2008 9:25 PM


Re: Running Farther
Or the breeding advantage of apparent bareness ... to the point where it threatened survival and clothes had to be invented for it to continue ...
Yup, getting a mate is high on the agenda at times. But I still doubt it is going to be one thing. And when it comes to mate selection, customs change. Look at Ruben's paintings.

Anyone so limited that they can only spell a word one way is severely handicapped!

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dwise1
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Message 26 of 27 (449749)
01-18-2008 9:44 PM
Reply to: Message 19 by RAZD
01-18-2008 8:56 PM


Of course, horses sweat over their entire bodies.
So sweating explains bare appearance in humans how?
The context would tell you what he was talking about. He was not talking about humans. He was pointing out a major difference between dogs and horses. You were the one who brought up horses.
The point was that, in terms of eliminating excess body heat through the ability to sweat and hence be cooled when that sweat evaporates, dogs are at a distinct disadvantage while horses fare better. And humans happen to fare even better, but what you responded to didn't say anything about humans.
The OP asks why lack of fur would be beneficial for humans. The ability to run without overheating is one. The question is not whether that is how or why that trait evolved, but rather why that trait would be advantageous.
BTW, note the common error expressed in the thread title. "positive Progression"? Evolution isn't about progress, but rather about adaptation.
A further thought about running occurred to me, though it's a bit off-topic. Thermo-regulation is only one factor. We are bipedal and the other animals we've discussed are quadrapedal. It would seem that the act of running would affect a quadraped's rib cage and hence its ability to breathe. It would seem that the stresses on the rib cage could make it harder to keep sucking in air at the rate that the animal's body would require for a long-distance run. As bipeds, we have two legs up (well, two forelimbs up, literally) on them by freeing our own ribcage from the stresses of running on our forelimbs, thus freeing us to suck air in at whatever rate we need.
Of course, that would need to be verified by somebody who actually knows something about it.

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Message 27 of 27 (449754)
01-18-2008 9:49 PM


Thread copied to the why is the lack of "fur" positive Progression for humans? thread in the Human Origins and Evolution forum, this copy of the thread has been closed.

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