Human genetic diversity,a critical resource for man's future

The human gene pool displays exuberant genetic variation; this is normal for a sexual species. Even small isolated populations contain a large percentage of the total variability, emphasizing the basic genetic unity of our species. As modern man spread across the world from its African source, the genetic basis for man's unique mental acuity was retained everywhere. Nevertheless, some geographical genetic variation such as skin color, stature and physiognomy was established. These changes were biologically relatively insignificant. Most of the genetic load in the genome has been carried throughout the history of the species. There is little hope of purging all of these harmful genes; we must accept them and continue to treat their syndromes medically. All populations carry extensive genetic variation due to genes that encode variations in quantitative traits. Of greatest importance among these is ubiquitous polygenic variability in brain function and intelligence. Mental acuity is what sets us apart from the rest of the biological world. Throughout our history, genetic recombination among the many genes involved in brain function has occurred. This has provided a genetic basis for the action of natural selection that favors intelligence in meeting the demands of the environment. As environments change in the future, this type of genetic variability will continue to be a crucial resource.This article is based on a contribution at the Session on Genetic Load chaired by Dr. Henretta Trent Band and presented at a meeting of the International Society for the History, Philosophy and Social Studies of Biology, Northwestern University, Evanston, Illinois in July 1991. The author is indebted to Professor Antonio Brito daCunha of the University of São Paulo, Brazil for his encouragement and comments.