magazine issue 9 2008 / Issue 8

Reconsidering Race in the Genetic Era

• written by Chris Buchholz
• edited by Abdolhossein Abdollahi

In light of the increasing prominence of genetics research in the media, it is important that the public understand the true complexity of human genetics and its relationship to race. Empirical studies in psychology have consistently demonstrated that most basic psychological processes do not differ significantly across cultural, ethnic, or racial groups. In other words, the basic physiology of our nervous system is essentially the same for all humans. When we do find minor differences in basic psychological processes such as visual perception or memory, instead of suggesting racial groups are fundamentally different, cross-cultural research has found evidence that these differences are due to a complex interaction between development and the socio-cultural environment (Ross & Milson, 1970; Segal, Campbell, & Hersokovits, 1963, 1966). In other words, psychological differences found between races are a result of the human mind’s ability to adapt to different environments. So, it is not race that determines differences in mental abilities across cultures, but the influence of culture and the environment. Nonetheless, there are, of course, some physical differences between members of different racial groups.

The most obvious difference, variation in skin color, appears to have evolved to help early humans adapt to a range of climatic conditions (Bamshad & Olson, 2003; Ossorio, 2006). Darker skin, for example, is associated with our ancestors that lived near the equator, where more radiation from the sun reaches the Earth.  Melanin, the hormone that produces skin pigmentation, works as a natural sunscreen protecting our body from harmful radiation. Even short-term exposure to ultraviolet (UV) radiation will result in an increase in melanin, temporarily darkening the skin (i.e., a suntan). Over thousands of generations, individuals that were better able to produce melanin were more likely to survive the harmful effects of UV exposure and thus more likely to live long enough to pass on their genes to their offspring.

On the other hand, we need to absorb some sunlight to enable our body to metabolize vitamin D. Human populations that migrated into northern climates gradually evolved to have less pigment in their skin. Less ultraviolet (UV) radiation reaches the surface as one moves away from the equator; therefore, melanin is not as crucial for survival in northern climates. Having too much melanin could even be harmful by preventing enough radiation to penetrate the skin to metabolize vitamin D. Also, consider that much of this change happened during an ice age, where humans dressed in clothes that covered most of their skin. This might have made the transition from dark to lighter skin occur at an accelerated rate because these humans had to absorb the required dose of sunlight through smaller patches of exposed skin (Ossorio, 2006). Overall, these climatic differences led to small mutations in the genes that produce melanin. In other words, differences in skin color are caused by small variations in the genes that are responsible for melanin, not because there are fundamentally different types of humans. Arguably, if you were to relocate lighter-skinned people to the equatorial region and those populations remained there for a few thousand years, their skin color would eventually become darker.