Human Variation

Human variation is also called as human variability, is the range of the possible values for any measurable feature, mental or physical of the human beings. Differences could be important or trivia, permanent or transient, involuntary or voluntary, acquired or congenital, environmental or genetic.  All living humans belong to a single genus and species, Homo sapiens. But this species is divided into subgroups, based on different frequencies of alleles for various physical traits. 

The old notion of race, which was often seen as a fixed and bounded population, has been supplanted by the concept of clinal variation. Anthropologists now speak about gradients or geographic distributions of specific variant traits, rather than about fixed races.

The basic principles of clinal studies are as follows:

• Gloger's Rule : Mammals and birds inhabiting warm and humid areas have darker skin pigmentation than those of the same species in cooler, drier areas; especially dry areas are marked by populations with yellow and/or reddish-brown pigmentation.
• Bergmann’s Rule: overall body size within the same species decreases in warmer areas, increases in cooler areas.
• Allen's Rule : The size of protruding body parts (e.g., tails, ears, bills) within the same species is reduced in  cooler areas and increased in warmer areas.

A geographic race is a localized population that has historically interbred more within itself than with outsiders. There may be physical barriers to interbreeding (e.g., mountains, seas). Traits that are particularly adaptive in a given area will be most frequent in populations historically localized in that area.

There is no scientifically documented relationship between race and intelligence. The capacity to learn is independent of the biological factors associated with the distribution of physical traits.

Questionnaire:

• What is human variability or human variation?
• Explain more about the human variability or human variation.