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Thread: Climate Rules for the Development of Body Characteristics

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    Post Climate Rules for the Development of Body Characteristics

    Bergmann's rule: body height

    Within a warm-blooded species, the races in the colder zones are usually bigger than those in warmer zones. There's a negative correlation between the average weight of a population and the average annual temperature of its living space; the higher the average annual temperature, the lower the average weight.
    The Indianids show a gradation of measures (height; head size) from the two cold zones up to the equatorial zone.

    Interpretation of this result of selection:
    Heat emission of the body is proportional to the surface, but heat production proportional to the volume of bodies. At bigger bodies the surface is in relation to the volume smaller.
    In colder climates the genetically bigger variants of a warm-blooded form survive better, as they can resist because of their relatively small surface (in relation to their volume) better against chilling through.

    Allen's rule: body extremities

    Allen's rule is in close connection to Bergmann's rule.
    Within a species, at the groups which live in a colder climate the distant body parts have a less share of the total surface than at those in colder climates.

    To make the relation between heat emission and production conveniant, those groups who are in colder climates tend to be rather stocky, while those who are in warmer climates tend to be rather slimm. An indicator is here the leg length, and this seems first as a contradiction to Bergmann's rule, as the leg length is in a relation to the total body length. A reducing of the leg length leads to a minor surface in relation to the volume, but also to a reducing of the heigth.

    The explanation is that when a small body is made bigger, but the parts keep the same proportions, the bigger body has less surface in relation to the volume than the smaller one had. But when a small body is made bigger through a lengthening of the legs, the parts of the bigger body show among themselves other proportions, and the surface of the body needn't become smaller in relation to the volume.
    So when in contrary to Bergmann's rule,populations are small in cold zones, they have relatively short legs, and when they are high in hot zones, they have relatively long legs (certain Negrid groups!).
    Allen's rule can be taken as a rule of proportion, the relation of body length to body mass.

    Allen's rule could also give an explanstion of the Mongolid facial flatness (which already Kant interpreted in 1775 as an adaption to cold climate):
    a) Reduction of facial surface to a minimum through flattening of all projections as much as possible.
    b) Padding of the surface with fat to prevent the loss of heat.
    c) Narrowing of the nasal passages, to give the air a maximum of heat at the way to the lungs.

    Gloger's rule: pigmentation

    In wet-warm climates the mellanin production is more intensive than in dry-cold ones, and so darker shades appear in those more often than in these.
    Melanin is produced through the occidation of tyrosin with the influence of ultraviolet rays and vitamin D.
    A strong pigment accumulation in the skin makes the UV radiation to a great extent inefective and therefor protects the organism from an oversupply of it. In zones o not much UV radiation a sparsely pigmented skin lets give the body enough UV radiation because of it being more pervious for UV radiation.

    As compensation of the danger of an overheating of the body,which is itensified because of that, strong pigmented populations like the Negrids have a good thermo-regulation through a higher number of sweat glands per skin surface and a higher intensity of sweat secretion.

    The itensity of UV radiation depends of the distance fromthe equator, sea level, clouds, humidity, air pollution, vegetation and reflexion capability of the ground.
    It is less intensive at the west coasts of the continents and in the temperate zones. It is more intensive in equator-near, dry zones, high mountain regions and in the arctic.

    Thomson-Buxton's rule: nasal breadth

    The nasal breadth plays also a role for thermo-regulation: Generally, the nasal index, the relation of nasal breadth to height, gets bigger from dry-cold to wet-warm climates.
    When the instreaming breath pillar passes a wide channel,it floods better and is less influenced by the warm mucous membranes; when the passage is narrow, the breath volume is devided in smaller streams, the flooding occurs slower, and it absorbes more heat from the surface which it passes.

    The nasal index is an indicator of the relation between the size of the nasal mucous membrans to the diameter of the breathing channel. Rather important than the warming is the moistening of the air. Very narrow noses are in dry-cold polar regions, narrow noses in the temperate zones and in dry-hot regions, very broad noses, very broad noses in wet-hot tropical zones.

    Based on information from:
    - Kenntner, Georg: Rasse aus Erbe und Umwelt. Der Mensch im Spannungsfeld seines Lebensraums, Berlin 1975.
    - Schwidetzky, Ilse: Rasse, in: Anthropologie (Fischer-Lexikon 15), ed. by Gerhard Heberer / Ilse Schwidetzky / Hubert Walter, Frankfurt a. M. and Hamburg 1970 (new edition), p. 187-215.
    Last edited by Nordgau; Thursday, March 11th, 2004 at 04:15 AM. Reason: Damned orthography error, just saw it...
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