Race: Biological Mechanisms

Figure 1.-- Here we see a group of children on the way to school in Xingu Indigenous Park, Brazil. The Amerindians in the Amazonian basin are the only important equatorial popularion which does not have very dark skin. An imprtant factor in genetic adapting to enviromental cinditions is time. Some anthropologists believe that a population needs to reside in an area for considerable time before environmental changes begin to be manifessted. This is perhaps 25,000 years or more, but there is no definatively established period. Amerindians are of course not indigenous to the Amazon or equatorial climes. They descended from Siberian hunters who crossed the Bearing Sea Ice Age land bridge about 11,000 BC and spent some time in Beringia before moving south.

Mutations appear to be the cause of genetic change. And this appears to be what has created the various races and other physical human differences. Most mutations are of no value and thus do not persist in the gene pool. If the mutation is beneficial and provides an evolutionary dvantage, than it can persist. This appears to have been what caused variation in skin color as humans moved out of Africa. Humans need sunlight to produce vitamin D. Yet dark skin filters outsunlight reducing vitamin D production in northerly latitudes. So individuals with lighter skin had a advantage leading to Europe and, especially Svandanavians, developing light skin. This is the process Darwin identified as natural selection. The development of blond hair is less clear. We know that polar animals have white hair which helps camouflage them while allowing sunlight to reach the skin. But given the small area of hair humans have, this mechanism seems less likely for people. It may be that skin and hair color genes are linked. But sexual selection may be at play. This seems the likely mechanism for blue eyes. This may also explain the persistance of the epicanthic eye fold. There are traits which have no survival value (for example the peacock's massive plumage), but appeal to the females. Many phyical characteristics are not associated with race. We note, for example, broad chests which facilate brearing among people living at high altitudes with low oxygen atmpsperes. We see this is the Andes and Himalayas. Another factor is time. People indigenous to equatorial areas have very dark skins. The principal exception is the Amerindian population in the Amazon Basin. Anthropologists believe that a population needs to reside in an area for considerable time before environmental changes begin to be manifessted.


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Created: 2:48 PM 2/10/2018
Last updated: 2:48 PM 2/10/2018