"Evolution of Skin Color" supported...

Discussion in 'Health and medical' started by James Michael H, Feb 27, 2004.

  1. selection, and skin colour," Evolution and Human Behavior 2004; 25: 38 which makes the connection of
    testosterone with skin color. I suggests this supports my "Evolution of Skin Color" at
    www.anthropogeny.com/evolution.html
     
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  2. Rick

    Rick Guest

    James Michael Howard <[email protected]> wrote in message news:<[email protected]>...

    > selection, and skin colour," Evolution and Human Behavior 2004; 25: 38 which makes the connection
    > of testosterone with skin color. I suggests this supports my "Evolution of Skin Color" at
    > www.anthropogeny.com/evolution.html

    Your statement: "According to my explanation of human evolution, lower testosterone groups migrated
    away from the equator. Therefore, it is the lower levels of testosterone that resulted in lighter
    skin in groups living away from the equator. Advantages of darker skin near the equator and
    advantages of lighter skin away from the equator are simply secondary advantages."

    That is counter-intuitive and human population movements were not "away from the equator" they were
    away from Africa which initially meant eastwards towards Java. Why did lower testosterone groups
    migrate? The picture you create is a group of humans who decided they'd had enough of all that
    testosterone flying around and moved away for a quieter life. Wouldn't it be easier to assume that
    humans spread over the world and each environment caused them to adapt differently?

    I'm more inclined to believe the theory that a lack of Vitamin D3, which causes rickets by blocking
    too much UV, is the selection pressure. In climates with less UV lighter skin is selected for. See
    http://www.earthlife.net/mammals/colour.html
     
  3. I invite you to look up Manning, et al., "Second to fourth digit ratio,

    25: 38 which makes the connection of testosterone with skin color. I suggests this supports my
    "Evolution of Skin Color" at www.anthropogeny.com/evolution.html

    You seem to think almost everything pertaining to human biology is caused or related to
    testosterone. Is the shape of one's nose related to testosterone?

    Michael Ragland
     
  4. On Sat, 28 Feb 2004 18:18:24 +0000 (UTC), [email protected] (Michael Ragland)
    wrote:

    >
    >I invite you to look up Manning, et al., "Second to fourth digit ratio,

    >25: 38 which makes the connection of testosterone with skin color. I suggests this supports my
    > "Evolution of Skin Color" at www.anthropogeny.com/evolution.html
    >
    >
    >You seem to think almost everything pertaining to human biology is caused or related to
    >testosterone. Is the shape of one's nose related to testosterone?
    >
    >Michael Ragland
    >

    Yes. I think "almost everything pertaining to human biology is caused [or directly affected by] by
    testosterone."
     
  5. On Sat, 28 Feb 2004 18:18:24 +0000 (UTC), [email protected] (Rick) wrote:

    >James Michael Howard <[email protected]> wrote in message
    >news:<[email protected]>...

    >> selection, and skin colour," Evolution and Human Behavior 2004; 25: 38 which makes the connection
    >> of testosterone with skin color. I suggests this supports my "Evolution of Skin Color" at
    >> www.anthropogeny.com/evolution.html
    >
    >Your statement: "According to my explanation of human evolution, lower testosterone groups migrated
    >away from the equator. Therefore, it is the lower levels of testosterone that resulted in lighter
    >skin in groups living away from the equator. Advantages of darker skin near the equator and
    >advantages of lighter skin away from the equator are simply secondary advantages."
    >
    >That is counter-intuitive and human population movements were not "away from the equator" they were
    >away from Africa which initially meant eastwards towards Java. Why did lower testosterone groups
    >migrate? The picture you create is a group of humans who decided they'd had enough of all that
    >testosterone flying around and moved away for a quieter life. Wouldn't it be easier to assume that
    >humans spread over the world and each environment caused them to adapt differently?
    >
    >I'm more inclined to believe the theory that a lack of Vitamin D3, which causes rickets by blocking
    >too much UV, is the selection pressure. In climates with less UV lighter skin is selected for. See
    >http://www.earthlife.net/mammals/colour.html

    My original idea was that breed and feed situations eventually result in increased testosterone.
    This resulted in pushing away of lower testosterone groups. I think this pushing is the main source
    of migration. Sure, groups may have been pushed easwards, but, at some, point, groups were pushed
    away from the equator.

    I guess you were being amusing when you described this in your response, but that is exactly what I
    intended. You have to explain your hypothesis that it would be easier to simply say the environment
    shaped humans. I do think the environment was involved, but it was extreme, long term environmental
    changes that were involved, such as extreme cold.

    Now, the work which prompted my post about this, Manning, et al., says, in their abstract: "The
    association between very dark skin and low latitude exists only when polygynoug societies are found
    at low latitudes, as is common in sub-Saharan Africa, but not in the New World." (Evolution and
    Human Behavior 2004; 25: 38-50). Of course, I suggest the darker skin and lack of monogamy result
    from increased testosterone.

    This was recently supported, too.

    Am J Phys Anthropol. 2003 Nov;122(3):279-86 Marriage, parenting, and testosterone variation among
    Kenyan Swahili men. Gray PB. Department of Anthropology, Harvard University, Cambridge,
    Massachusetts 02138. Male variation in testosterone (T) levels may, in part, reflect a differential
    behavioral allocation to mating and parenting effort. This research tests whether demographic
    indicators of pair bonding and parenting were associated with salivary T levels among Kenyan Swahili
    men. Men in the sample were either unmarried (N = 17), monogamously married (N = 57), or
    polygynously married (N =
    14), and between ages 29-52. In contrast with earlier findings among North American men,
    monogamously married men did not have lower T levels than unmarried men. However, among all
    married men, men with younger genetic children tended to have marginally lower T levels.
    Polygynously married men, all of whom had two wives, had higher T levels than all other Swahili
    men. Possible explanations of higher T levels among polygynously married men are explored. Am J
    Phys Anthropol, 2003. Copyright 2003 Wiley-Liss, Inc.
     
  6. On 2004-02-29, James Michael Howard <[email protected]> wrote:

    [snip]

    > tended to have marginally lower T levels. Polygynously married men, all of whom had two wives, had
    > higher T levels than all other Swahili men.

    [snip]

    I haven't read the paper, but at first glance this hardly seem surprising. Something for the Ignobel
    prize, perhaps?

    AC

    --
    Using Linux GNU/Debian - Windows-free zone http://www.acampbell.org.uk (book reviews and articles)
    Email: replace "www." with "[email protected]"
     
  7. Rick

    Rick Guest

    James Michael Howard <[email protected]> wrote in message news:<[email protected]>...
    > On Sat, 28 Feb 2004 18:18:24 +0000 (UTC), [email protected] (Rick) wrote:
    >
    > >James Michael Howard <[email protected]> wrote in message
    > >news:<[email protected]>...

    > >> selection, and skin colour," Evolution and Human Behavior 2004; 25: 38 which makes the
    > >> connection of testosterone with skin color. I suggests this supports my "Evolution of Skin
    > >> Color" at www.anthropogeny.com/evolution.html
    > >
    > >Your statement: "According to my explanation of human evolution, lower testosterone groups
    > >migrated away from the equator. Therefore, it is the lower levels of testosterone that resulted
    > >in lighter skin in groups living away from the equator. Advantages of darker skin near the
    > >equator and advantages of lighter skin away from the equator are simply secondary advantages."
    > >
    > >That is counter-intuitive and human population movements were not "away from the equator" they
    > >were away from Africa which initially meant eastwards towards Java. Why did lower testosterone
    > >groups migrate? The picture you create is a group of humans who decided they'd had enough of all
    > >that testosterone flying around and moved away for a quieter life. Wouldn't it be easier to
    > >assume that humans spread over the world and each environment caused them to adapt differently?
    > >
    > >I'm more inclined to believe the theory that a lack of Vitamin D3, which causes rickets by
    > >blocking too much UV, is the selection pressure. In climates with less UV lighter skin is
    > >selected for. See http://www.earthlife.net/mammals/colour.html
    >
    >
    > My original idea was that breed and feed situations eventually result in increased testosterone.
    > This resulted in pushing away of lower testosterone groups. I think this pushing is the main
    > source of migration. Sure, groups may have been pushed easwards, but, at some, point, groups were
    > pushed away from the equator.
    >
    > I guess you were being amusing when you described this in your response, but that is exactly what
    > I intended. You have to explain your hypothesis that it would be easier to simply say the
    > environment shaped humans. I do think the environment was involved, but it was extreme, long term
    > environmental changes that were involved, such as extreme cold.
    >
    > Now, the work which prompted my post about this, Manning, et al., says, in their abstract: "The
    > association between very dark skin and low latitude exists only when polygynoug societies are
    > found at low latitudes, as is common in sub-Saharan Africa, but not in the New World." (Evolution
    > and Human Behavior 2004; 25: 38-50). Of course, I suggest the darker skin and lack of monogamy
    > result from increased testosterone.
    >
    > This was recently supported, too.
    >
    > Am J Phys Anthropol. 2003 Nov;122(3):279-86 Marriage, parenting, and testosterone variation among
    > Kenyan Swahili men. Gray PB. Department of Anthropology, Harvard University, Cambridge,
    > Massachusetts 02138. Male variation in testosterone (T) levels may, in part, reflect a
    > differential behavioral allocation to mating and parenting effort. This research tests whether
    > demographic indicators of pair bonding and parenting were associated with salivary T levels among
    > Kenyan Swahili men. Men in the sample were either unmarried (N = 17), monogamously married (N =
    > 57), or polygynously married (N =
    > 14), and between ages 29-52. In contrast with earlier findings among North American men,
    > monogamously married men did not have lower T levels than unmarried men. However, among all
    > married men, men with younger genetic children tended to have marginally lower T levels.
    > Polygynously married men, all of whom had two wives, had higher T levels than all other Swahili
    > men. Possible explanations of higher T levels among polygynously married men are explored. Am J
    > Phys Anthropol, 2003. Copyright 2003 Wiley-Liss, Inc.

    I think the testosterone angle is interesting but don't accept that it is reason for the spread of
    humans around the globe. My interpretation of your hypothesis is that those who have migrated the
    furthest are likely to have the lightest skins. The people who have migrated the furthest are those
    living in South America, or in terms of difficulty of passage it would be the Polynesians in places
    like Hawaii. These people do not have white skin (or hair) but people from the north of Eurasia,
    like Scandinavians, do.

    It is natural for populations to spread because: a given area of land could only support so many
    people, hunters followed game, new tribes formed and separated either because the original tribe got
    too big or they fell out for whatever reason. Having spread themselves into new environments there
    would be selection pressure for certain things including the UV resistance of the skin.

    I don't deny that there seems to be a connection between very dark skin in polygynous tribes in
    Africa and testosterone levels. By that definition it is a local effect and would not be the primary
    reason for the global differences in skin colour. First you need to establish the cause and the
    effect. It could be that higher testosterone levels are the effect rather than the cause, or maybe
    none of them are the cause.
     
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