Why do we get wisdom teeth?

Discussion in 'Biology & Genetics' started by visceral_instinct, Feb 1, 2009.

  1. Roman Banned Banned

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    Wisdom teeth arrive by the time you're in your twenties. Average life span of our prehistoric ancestors is estimated around 35 years. I've read that a major contribution to mortality was our teeth wearing out and us not getting a second pair.

    As for life span, maximum human life span hasn't changed in recorded history. Maybe by a few percent, from 105 to 110. Average life span has increased a great deal, but despite all our advances in science & medicine, age limits haven't changed. Why this is is subject to a great deal of debate and research, and at the moment, is probably outside of our ability to change. Hard to lengthen telomeres, reduce oxidative stress from respiration, and make immortal stem cells that don't turn into cancer with our current knowledge of molecular biology.
     
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  3. CutsieMarie89 Zen Registered Senior Member

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    My biology professor and my boss at the museum both said that humans are losing teeth. Which is why quite a large number of people are born missing wisdom teeth. Natural selection at work I guess :shrug: I only had three of them and had them removed because they were growing underneath my other molars, glad their gone.
     
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  5. Enmos Staff Member

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    Can we assume that people that did get older didn't have rotting wisdom teeth from age 20 on ?
    Of course some people got older. But due to lack of medical care and a hard life people on average didn't get very old.
     
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  7. Enmos Staff Member

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    It's more like natural indifference

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  8. Enmos Staff Member

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    That makes sense. But fact is that most wisdom teeth are quite useless today. They remain impacted, come out sideways etc.
    I think both theories ('shorter jaws while same size teeth' and 'wisdom teeth are back-up teeth') are right.

    Agreed.
     
  9. Roman Banned Banned

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    What selection, though?
     
  10. Enmos Staff Member

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    Unselection.
     
  11. Orleander OH JOY!!!! Valued Senior Member

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    on average no, but that's not what you said. You said they didn't get as old. They did, just not in the quantity we do. So I accept your apology.
     
  12. Roman Banned Banned

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    You mean drift?
    Or selection against growing teeth because it's costly and unnecessary, so those who don't grow teeth have a slight energy advantage over those who don't?
     
  13. Fraggle Rocker Staff Member

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    There have always been statistical outliers, but the average life expectancy dropped precipitously after the Agricultural Revolution, when Neolithic humans began subsisting on grains instead of meat and their civilized descendants became even less carnivorous. Skeletons dug up of the last of the hunter-gatherers show that the life expectancy of an adult who had survived childhood (no mean feat of course) was in the low fifties. By the Roman era it had dropped to the low twenties. Prosperity increased the meat in the diet and by the end of the 19th century life expectancy (of adults) in the USA was back up into the thirties. Antibiotics, asepsis and vaccinations reduced infant mortality, the discovery of vitamins and minerals gave everyone a healthier diet even if they insisted on eating too many vegetables, hospitals allowed more women to survive childbirth and automation allowed men to take jobs that were less life-threatening, so the life expectancy of adults has doubled, and the life expectancy at birth has more than tripled.

    And of course dentistry and fluoride have helped us all keep more of our teeth.

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    Natural selection only takes place if the trait in question is actually selected for or against, either by survival or mating practices. No one dies because they have wisdom teeth, and I have to say I have never heard of anyone counting a prospective mate's teeth before deciding to procreate with them.

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    However, they do that with horses.

    Count the teeth, not procreate.
     
  14. Roman Banned Banned

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    That's nice Fraggle, but despite all those advances in health care and medical science, the maximum life span hasn't changed in recorded history. The biological and physioloigcal factors for human lifespan have remained the same, despite changes in environmental factors.

    Of course, when it comes to explaining selection, average life span is a much better metric than maxima.

    I know you didn't say this, but if selection isn't acting on a trait, evolution can still occur there, and very often does. This is called drift, and is a product of a finite population. Hardy-Weinberg equilibrium exists if there is random mating and an infinite number of alleles to draw from, and no selection. However, neither of the former two assumptions are true outside of the model, especially for the patchy distribution of macro-fauna, like most mammals and birds. Because of this, you can still have changes in gene frequency (evolution) without any selection occurring.

    This drift is taken advantage of with genetic fingerprinting, since there are regions of our genome that, as far as we know, aren't being used for anything. These regions used to be called junk DNA because they didn't code for a functional product, but much of that "junk" is actually active in other ways. These genomic regions that don't appear to be doing anything have high mutation rates, which, because the DNA doesn't code for anything or function in any way, don't affect the organism. Since these mutations occur at random, if you look at enough loci where random mutations occur, it is very unlikely that two people will have the exact same mutations.
     
  15. Syzygys As a mother, I am telling you Valued Senior Member

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    That is debatable and we just don't know. If the oldest person is 122 now and 1000 years ago it was 105 that is still almost 20% increase, but I agree with Fraggle that those are statistical outliers, we should look at groups instead of individuals....

    http://en.wikipedia.org/wiki/Maximum_life_span#In_humans

    It would be better to look at the 10 or 50 oldest persons in a decade or century, and average their ages of death and see if there is a statistically valid difference...

    The problem is that before the 18th century it is pretty much impossible to verify a person's both birhday and day of death, when the person is over 100 years old...

    It could be argued though that people 1-2000 years ago geneticly were able to live just as long as now, but other circumstances shortened their lifes....

    ------------------------

    I started a new thread with this topic here:

    http://sciforums.com/showthread.php?t=90296

    Since this is an interesting but offtopic here, please respond to it in its own thread...
     
    Last edited: Feb 1, 2009
  16. CutsieMarie89 Zen Registered Senior Member

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    I don't know. I was just listening to my academic superiors. My professor said he didn't know why either, but people have much fewer teeth than most mammals. For whatever reason nature seems to favor humans that have fewer teeth. Otherwise there wouldn't be so many people missing one or more wisdom teeth. It's rare that people are missing their incisors. I'm just speculating obviously, but it seems like there is some sort of selective pressure at work. Whether it's actually something physical or if it's just genetic drift...
     
  17. Orleander OH JOY!!!! Valued Senior Member

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    I understand that Fraggle, but that's not what he said.
     
  18. Enmos Staff Member

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    Nice try

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  19. Enmos Staff Member

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    Drift yea, and random mutation.

    If they aren't being used there is no natural selection working to keep them in good shape, so they deteriorate.
     
  20. Enmos Staff Member

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    That IS what I said. lol
     
  21. Orleander OH JOY!!!! Valued Senior Member

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    where did you say that?
     
  22. Enmos Staff Member

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    Jesus Christ Orleander..

    "They didn't get as old as we do". "They" refers to the people that lived back then. Them, the people.. as a group.

    :bugeye:
     
  23. Orleander OH JOY!!!! Valued Senior Member

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    Uh-huh. :xctd:
    Its your story, you can tell it any way you want I guess.

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