Why are we near hairless?

Discussion in 'Biology & Genetics' started by wise acre, Apr 30, 2009.

  1. mikenostic Stop pretending you're smart! Registered Senior Member

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    LOL WUT?

    By me stating that the plains animals also have fur was more or less a general factual statement. And it seems you are trying to argue my factual statement with two factual, but more specific statements. I don't get it. It's like trying to divide by zero or something.
     
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  3. Search & Destroy Take one bite at a time Moderator

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    A general factual statement, true

    me:

    you:
    I thought that yet was an on the contrary. But now I see your point clearly. I knew I missed something. Anyway, carry on
     
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  5. tuberculatious Banned Banned

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    Fur is even useful in water.
     
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  7. wynn ˙ Valued Senior Member

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    ?

    Perhaps humans chose to mate selectively - ie. to mate with the less hairy fellow humans.

    Just like some people like hairless animals, perhaps 'our ancestors' preferred the less hairy or hairless natural mutations of humans.
     
  8. mikenostic Stop pretending you're smart! Registered Senior Member

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    True. But that only applies to animals that don't spend 100% of their time in water. To name a couple...
    -polar bears. Their fur helps their buoyancy and since it's hollow, provides a 'greenhouse' warming effect.

    -otters. Insulation for warmth.
     
  9. tuberculatious Banned Banned

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    987
    This one spends almost 100% of its time in the water.
     
  10. CutsieMarie89 Zen Registered Senior Member

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    But some people have a lot of hair and left unchecked (unshaven/uncut) would have a great deal of it, enough to be considered a thin coat at least. So perhaps it was a sexual selection thing, but then that kind of runs contrary to hair being a secondary sex trait, meaning it doesn't grow until one is approaching sexual maturity (which includes I guess almost all hair except the hair on the head). Perhaps child like appearances are sexy to people?
     
  11. iceaura Valued Senior Member

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    24,097
    The one plausible theory I have seen comes from biologists who study the niche of heat adaptation - many animals have adapted to withstand hotter temps than their prey or predators, and thus can forage or hide or otherwise outcompete others for ecological niches.

    Tiger beetles on sandy beaches in the daytime, for example - a rich area of food, and too hot for most beetle enemies or competitors.

    The theory is that humans - apparently already upright walkers and tool users, btw - found that ability to travel and hunt and forage and run in the heat allowed them to scavenge and gather over large areas while avoiding heat-vulnerable predators and capturing heat-vulnerable prey, and opened up a large niche for them. This ability would have incremental payoffs (a little less hair is a little more advantage) as required by evolutionary theory, and dovetails neatly with sexual selection and the other observed influences.
     
  12. wise acre Registered Senior Member

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    725
    But grooming creates tight social bonds.

    I think that suggests that the chemicals we use for this are partially poison.

    This is my favorite.
     
  13. wise acre Registered Senior Member

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    725
    Hey,
    Lamark is coming back...
    epigenetics!
     
  14. wise acre Registered Senior Member

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    725
    Abrasion. Perhaps it was the women. Perhaps intelligence is the factor. IOW women decided they had a preference and did conscious maneuvering.
     
  15. wise acre Registered Senior Member

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    725
    But in Africa there seem to be many predators that run in the heat. All hairy.
     
  16. wynn ˙ Valued Senior Member

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    Sure. But with all their new intelligence, the 'early humans' probably found new ways of bonding, such as making pots, clothes, spears and all that. Surely it is nicer to give a potential mate or friend a nice piece of jewelery (even if it is made out of a boar's claw), than pick them for lice and fleas, no? Perhaps 'early humans' discovered pride and shame!

    Or, because their new intelligence was used up for hunting and roasting meat, they neglected bonding, and the fur wasn't useful anymore as a medium of bonding.


    Or perhaps at some point in the past, 'early humans' used some nasty stuff to wash themselves for long enough to produce lasting changes.

    Or perhaps they were exposed to radiation.


    Absolutely. Seriously, since 'early humans' had greater intelligence than their ancestors, it is only reasonable to ask how this intelligence manifested, and how this in turn can be related to hairloss.


    (Just brainstorming.)
     
  17. wise acre Registered Senior Member

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    725
    Perhaps hairlessness is causal here not intelligence. Mutations led to hairlessness which led to more complicated strategies in maintaining body temperature which selected for larger brains.

    Notice that dolphins and whales, with very large brains, are also mammals - once land based - who are hairless.

    Chimps have hairless faces which gave them an edge.
     
  18. wynn ˙ Valued Senior Member

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    15,058
    Perhaps they are parallel, mutually enhancing eachother?

    Living systems are complex; it is therefore likely that in order for a particular trait to result, a complex causation was in place.
     
  19. iceaura Valued Senior Member

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    There aren't - not like humans. The big predators of Africa lay up in the middle of the day for good reason - endurance in the heat is a serious limitation for them (the lions of the hotter regions grow much smaller and lighter manes, leopards and other dangerous predators of hominids hunt in the evening and morning when it's cool, everything beds down in the shade in hot, dry country).

    And the advantage is not just predator avoidance, but foraging and scavenging range across dry country away from the safety of trees or other hides, and transport range for discovered food, and migration ability in harsh heat, and so forth. A pack of humans that can travel fast in the heat can rob kills miles away and bring the meat back to safety before evening brings out the leopards and hyenas, can live farther from dangerous water holes and not visit them in the mornings, and similar advantages.

    And once the modern form was established, an entire new world of hunting strategies opened up - humans can kill most antelope and similar animals simply by running them down under the sun and hitting them with a rock, for example.

    The advantages of the explanation are that it is incremental, it is supported by the known physical circumstances of early human life, it does not require fanciful assumptions like an entire group developing a sexual preference for hairlessness without any advantage (or overcoming a Zahavian handicap of some unspecified kind), and it fits the current physiology of humans compared with other animals - we can in fact travel and work and run in the heat to a very unusual degree, for a mammal, and largely as a consequence of our hairlessness and a couple of related adaptations in blood circulation and sweat glands.

    Like I said, it's not a locked in explanation - but it's one of the few with even a lick of sense to them. We see the physiological advantages of hairlessness now, and it's not a great leap to hypothesize them as the advantages driving the acquisition of the trait.

    Equally likely, from a complex system, is a complex reaction to a simple selective pressure.
     
  20. madanthonywayne Morning in America Staff Member

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    Did you read this bit of that article?
    Harris suggests that Neanderthals must have been furry in order to survive the Ice Age. Our species would have seen them as "animals" and potential prey. Harris' hypothesis continues that Neanderthals went extinct because human ancestors ate them.

    I've long believed that modern humans wiped out the Neanderthals, but I never thought we ate them. As to the actual hypothesis, I think we lost our hair simply because we didn't need it. Absent a selective pressure to maintain body hair, we lost it.

    PS I just read Iceaura's hypothesis and, I never thought I'd have the chance to say this, it makes sense.
     
  21. wise acre Registered Senior Member

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    All very reasonable. But then you'd think there'd be one hairless feline or canine species that slid into a similar advantage.
     
  22. wise acre Registered Senior Member

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    I'm assuming you mean we did not need it for warmth. ?
    If so, is there anything to back this up in natural selection as humans emigrated from Africa? IOW are people in colder regions more likely to have more body hair?
     
  23. madanthonywayne Morning in America Staff Member

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    We didn't need it for anything. We could wear clothes to take the place of hair when needed, and have all the advantages of not having hair Ice made reference to other times.
     

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