Human Variation

One way researchers break down variation is by separating genetic and environmental components. By dividing the amount of influence each type of variation has on the phenotype of an individual, researchers attempt to quantify the genetic basis of physical and/or behavioral characteristics. However, an accurate measure of the exact impact of environmental vs. genetic factors is very difficult (if not impossible), particularly because of the fact that human beings are constantly exposed to both factors simultaneously immediately after birth.

Genetic Variation

Variation can be maintained within a population in several instances, such as:

• heterozygotes having a selective advantage
• environment has changed recently, but gene pool has not shifted accordingly
• more than one allele provides the same function with equal success

Between group variation is often maintained through different selective environments associated with regions. Characteristics which may be beneficial in a cold weather environment may prove to be cumbersome and inefficient in hot climates, and vice versa. Also, variation may be a by-product of a strong founder effect, where a population's genetic composition is altered by breeding isolation and a small initial gene pool. Since mutation and drift will tend to make any two given populations increasingly different (just as gene flow will homogenize them), patterns of population differentiation become a historical source for demographics and population movement.

These patterns of genetic variation allow researchers to reconstruct migrational events and population expansions associated with related groups of people. Various studies of mitochondrial DNA (mtDNA) have suggested a worldwide population expansion and migration approximately 100,000 years ago.

Understanding Human Variation

The instance in which ideas about human variation are most abused is in the context of racial classification. Common racial classification apportions human variation in a flawed and biased manner. Three of the more common misconceptions include:

1. human beings naturally divide into a small number of distinct races
2. races have certain inherent strengths and weaknesses, particularly in terms of intelligence, morality, and character
3. racial differences are due to definite biological heritage

The principle problem of this view from a scientific standpoint is that each statement is substantiated less by the biological data and more by certain political and ideological perspectives. The amount of genetic variation between different groups of humans is very low overall, and a number of arbitrary groups can be created based on different criteria. It just so happens that certain phenotypic characteristics (e.g., color of skin, shape of eyes, consistency of hair) are emphasized in typecasting individuals along common views of race, a practice which inevitably provides little useful information.

When examining the biological basis of race and racial conflict, events in the past have had a clear cultural (e.g., political, religious) basis; this being the case, it does not follow that the major source of this difference is biological in nature. While this is not to say that there is no biological variation between different populations of people, the biological distinctions are much more opaque than implied by common notions of race. Oftentimes the reliance on race as a biological concept serves more of a political and social end - by creating an immutable difference between peoples - one that has never existed biologically. To see some examples, and learn more about the detrimental effects of racism, click here.