[Tres Juicy]

Mike Waller, on 27 January 2012 - 10:44 AM, said:

A controversial idea put out about 20 years ago was that the use of fire was the key event; the point being that hairy creatures playing with fire are quite likely to incinerate themselves. Many on the the list I was then on were very strongly opposed to this (to a degree that was well beyond the merits or otherwise of the suggestion) but when I experimentally put a match to the hair on my forearm I was surprised at how much it flared up. I should say that I suffered no permanent harm!

Very doubtful.

[Mike Waller]

Tres Juicy, on 27 January 2012 - 12:22 PM, said:

Very doubtful.

Thank you for your detailed contribution to the scientific debate!!!!!!

[Tres Juicy]

Mike Waller, on 27 January 2012 - 05:26 PM, said:

Thank you for your detailed contribution to the scientific debate!!!!!!

I could elaborate by saying that it is highly unlikely that fire and people incinerating themselves could possibly cause enough selection pressure to make us lose most of our hair as a result

But do I really need to?

[shawnhcorey]

Mike Waller, on 27 January 2012 - 10:44 AM, said:

A controversial idea put out about 20 years ago was that the use of fire was the key event; the point being that hairy creatures playing with fire are quite likely to incinerate themselves. Many on the the list I was then on were very strongly opposed to this (to a degree that was well beyond the merits or otherwise of the suggestion) but when I experimentally put a match to the hair on my forearm I was surprised at how much it flared up. I should say that I suffered no permanent harm!

I think this is unlikely. That our hairy ancestors played around with something as hazardous as fire until their descendants could evolved a means to reduce the hazards seems unlikely. It's more likely they would stop the first time they were burnt and their descendants would never need to get less hairy. In other words, our ancestors were pretty much hairless when they started using fire.

[Mike Waller]

Tres Juicy, on 27 January 2012 - 05:31 PM, said:

I could elaborate by saying that it is highly unlikely that fire and people incinerating themselves could possibly cause enough selection pressure to make us lose most of our hair as a result

But do I really need to?

It might perhaps be considered a matter of good list etiquette.

shawnhcorey, on 27 January 2012 - 05:32 PM, said:

I think this is unlikely. That our hairy ancestors played around with something as hazardous as fire until their descendants could evolved a means to reduce the hazards seems unlikely. It's more likely they would stop the first time they were burnt and their descendants would never need to get less hairy. In other words, our ancestors were pretty much hairless when they started using fire.

I have no strong views either way but was very annoyed on the occasion on which I first hear the idea aired to see the guy who had the imagination to put it forward simply given, as we say, a good kicking for his troubles. This has never seemed to me a good way to progress the scientific debate. There may, of course, be incontravertible evidence of some kind that proves the two events were wholey unrelated; but failing that it seems to me obvious that the interplay between proto-humanity and fire would be a lot subtler that that of the more hairy individuals simply getting burned to death.

Off the top of my head I would say that fire confers at least four major advantages: the cooking of food stuffs which, I think, aids digestion; the giving of illumination at night so that work can be done at a time when it would otherwise be impossible; providing some protection against predators who either fear the fire itself or the lighted brands that can be taken from it; and land clearance. Assuming as you say, that hairier individuals, having be burned by it, chose to avoid it altogether, the adaptive advantage on those who decided to stick with it would be substantial, And it would seem to me obvious that the less hairy would be prominent amongst the stickers.

Incidental years ago I read a folk tale from China which gave an account of how the Chinese came to eat pork. It turned upon a pre-pork eating society (but why would they have pigs?) in which a particular peasant's pig house burned down. Experimentally trying the meat, he found it so delicious that he had to have more and thus the world received the gift of sweet and sour pork! . Whatever the truth of that, it does seem to me pretty likely that groups of hominids coming across burned corpses following forest fires would find meat not entirely charred very much to their taste and would seek out way of producing this to order. Certainly I have never know a dog turn its nose up at cooked meat.

This post has been edited by Mike Waller: 28 January 2012 - 11:56 AM

[shawnhcorey]

Mike Waller, on 28 January 2012 - 11:53 AM, said:

Assuming as you say, that hairier individuals, having be burned by it, chose to avoid it altogether, the adaptive advantage on those who decided to stick with it would be substantial, And it would seem to me obvious that the less hairy would be prominent amongst the stickers.

That's what I said, the less hairy would stick with it. That means, of course, that they were less hairy to start with; something else cause they to evolve the reduction of hair.

[Mike Waller]

shawnhcorey, on 28 January 2012 - 01:47 PM, said:

That's what I said, the less hairy would stick with it. That means, of course, that they were less hairy to start with; something else cause they to evolve the reduction of hair.

Natural variability is one of the bedrocks of evolution. A re-occuring mutation which might once have been an actual disadvantage or a disadvantage in terms of acceptability in the context of sexual selection, suddenly becomes something positive. There does not have to have been an environmental factor that favoured it previously. Which is not, of course, to say that there wasn't something that did so favoured it.

[Santalum]

Mike Waller, on 28 January 2012 - 09:14 PM, said:

Natural variability is one of the bedrocks of evolution. A re-occuring mutation which might once have been an actual disadvantage or a disadvantage in terms of acceptability in the context of sexual selection, suddenly becomes something positive. There does not have to have been an environmental factor that favoured it previously. Which is not, of course, to say that there wasn't something that did so favoured it.

Surely there can be no other logical explanation other than the fact that humans, unlike all other mammals, have very well developed sweat glands as a means of cooling ourselves and that sweating does not work with a full or signficant coat of hair.

Combined with the fact that humans are accomplished persistance hunters where long endurance under sustained exertion, that no other mammals possess, is absolutely essential.

It is pretty clear that there would be strong selection pressure for hairlessness under the above circumstances.

The other apes are not persistance hunters and hence there has not been as strong selection for hairlessness among them.

Quote

Apocrine sweat glands are larger, have different mechanism of secretion, and are limited to axilla (armpits) and perianal areas in humans. Although apocrine glands contribute little to cooling in humans, they are the only effective sweat glands in hoofed animals such as the donkey, cow, horse, and camel.^[2][3] Most other mammals, such as cats, dogs and pigs, rely on panting or other means for thermal regulation and have sweat glands only in foot pads and snout. The sweat produced on pads of paws and on palms and soles mostly serves to increase friction and enhance grip.

Presumeably this type of sweat gland in hoofed animals is not as effective as, from inumerably documentaries, human hunters are nearly always able to run down hoofed animals as long as they can track them. I believe that hoofed animals are still reliant on panting etc to some extent to assist in cooling themselves and they have to stop running in order to do that.

Quote

Abstract
Mammals have two kinds of sweat glands, apocrine and eccrine, which provide for thermal cooling. In this paper we describe the distribution and characteristics of these glands in selected mammals, especially primates, and reject the suggested development of the eccrine gland from the apocrine gland during the Tertiary geological period. The evidence strongly suggests that the two glands, depending on the presence or absence of fur, have equal and similar functions among mammals; apocrine glands are not primitive. However, there is a unique and remarkable thermal eccrine system in humans; we suggest that this system evolved in concert with bipedalism and a smooth hairless skin.

http://books.google....olution&f=false

Also from this website it is more specifically day time persistance hunting that produced strong selection pressure for hairlessness in humans. A great many other predators hunt mainly at night when it is cooler.

Quote

Persistence hunting is a hunting technique in which hunters use a combination of running and tracking to pursue prey to the point of exhaustion. While humans can sweat to reduce body heat their quadruped prey would need to slow from a gallop to pant.^[1] Today, it is very rare and seen only in a few groups such as Kalahari bushmen and the Tarahumara or Raramuri people of Northern Mexico. Persistence hunting requires endurance running – running many miles for extended periods of time. Among primates, endurance running is only seen in humans, and persistence hunting is thought to have been one of the earliest forms of human hunting, having evolved 2 million years ago.


Contents
[hide]

• 1 Persistence hunting in human evolution
• 2 Procedure
• 3 Persistence hunting among cultural groups
• 4 See also
• 5 References
  • 5.1 General
  • 5.2 Notes
• 6 External links

Persistence hunting in human evolution
Further information: Endurance running hypothesisThe persistence hunt may well have been the first form of hunting practiced by hominids. It is likely that this method of hunting evolved before humans invented projectile weapons, such as darts, spears, or slings. Since they could not kill their prey from a distance and were not fast enough to catch the animal, one reliable way to kill it would have been to run it down over a long distance.

In this regard one has to bear in mind that, as hominids adapted to bipedalism they would have lost some speed, becoming less able to catch prey with short, fast charges. They would, however, have gained endurance and become better adapted to persistence hunting.^[2] Although many mammals sweat, few have evolved to use sweating for effective thermoregulation, humans and horses being notable exceptions. This coupled with relative hairlessness would have given human hunters an additional advantage by keeping their bodies cool in the midday heat.

This post has been edited by Santalum: 1 February 2012 - 10:44 PM