The Gloger rule is a biological rule that states that in a kind of hot blood (endotherms), the most heavily pigmented shapes tend to be found in humid environments, that is near the equator. It was so called in honor of the zoologist Constantin Wilhelm Lambert Gloger, who first observed and defined this phenomenon in 1833 in a publication on the covariance of the bird's plumage climate and color (Erwin Stresemann notes that the idea had already been expressed by Pallas in Zoographia Rosso-Asiatica (1811)). Gloger noted that the birds of the more humid habitats tend to be darker than those that populate regions with greater aridity. Over 90% of the 52 North American species observed follow this rule.
An explanation of Gloger's rule for the bird's case seems to be an enhanced resistance of dark pencils to bacteria that degrade pen and hair, such as Bacillus licheniformis. Pens in moist environments have a higher bacterial charge and humid environments are more suitable for bacterial growth; dark pens or dark hair are more resistant to degradation. Eumelanins, more resistant and dark brown to black, are accumulated in warm and humid regions, while arid regions dominate the yellow-sandy reddish-yellow pheomelanine for the beneficial effect of the crips.
Among mammals, there is a marked tendency to have the darkest skin color in equatorial and tropical regions compared to individuals of high latitutins. In this case, the underlying cause could be the best protection against excessive exposure to solar UV radiation occurring at low latitudes. However, the absorption of a certain amount of UV radiation is essential for the production of certain vitamins, particularly vitamin D (see Osteomalacia).
This principle has also been widely demonstrated among human populations. Populations that evolved in the sunnier surroundings closer to the equator tend to be darker pigmentation than populations originated from sites that are more distant from the equator. There are, however, exceptions: among the best-known are the Tibetans and the Inuit, who have a darker skin than they could expect for their latitudes of origin. In the first case, there seems to have been an adaptation to the intense irradiation from UV radiation on Tibetan Plateau, while in the second case the need to absorb UV radiation is reduced by the Inuit diet, which is naturally rich in Vitamin D. Notemodify wikitesto Voices correlateemodify wikitesto Bibliografiamodifica wikitesto
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