Immunological Uniformity

One of the mechanisms that allows for environmental adaptation and evolution through artificial (i.e. mate) selection is genetic variation (Maitland & Johanson, 2002).

This is crucially important in immunology because a varied genetic pool allows successive generations within any species to adapt to environmental threats. Likewise, immunological and chemical variation allows for the survival of portions of a given population even after a specific environmental threat kills or sterilizes many individuals.

Conversely, gene pool uniformity would put the entire species at risk to environmental threats because the only mechanism available for adaptation would be evolution through

spontaneous mutation, which does not generally produce beneficial changes within a single successive generation (Maitland & Johanson, 2002).

A perfect example of the way that genetic immunological variation works is the major histo-compatibility (MHC) gene, an important component of human immunology

(Maitland & Johanson, 2002). Specifically, in humans, the scent of male sweat transmits important signals to females that either enhances or diminishes potential sexual attraction.

The process is largely subconscious on the part of the female, but they are more sexually attracted to males whose sweat indicates that their MHC genes differ from those of the female. Significantly, this is only true during the portion of the monthly menstrual cycle where pregnancy is possible, strongly suggesting that its purpose is to ensure maximal immunological variation in offspring. At other times of the month, human females

respond more favorably to the odor of male sweat that indicates similar MHC genes in the male instead of different MHC genes from the female. It has been theorized that this is the other element of a dual-role mechanism that also promotes family unity while also decreasing the risk of pregnancy through incest while the female lives with the family of origin (Maitland & Johanson, 2002).

References

Maitland, a., and Johanson, D. (2002). Blueprints: Solving the Mystery of Evolution.

New York: Penguin.