Genetic relationship of human populations and ethnic differences in reaction to drugs and food.

Using gene frequency data for a large number of protein and blood group loci and restriction-site data for mitochondrial DNA, we studied the genetic variation within and between the three major races of man, Caucasoid, Negroid, and Mongoloid. In all the three major races, about 50 percent of structural loci seem to be polymorphic at the electrophoretic level, and the average heterozygosity is about 14 percent. The genetic variation between the three major races is small compared with that within the races. However, even this small interracial variation seems to be the result of geographic isolation for 40,000 to 110,000 years. Genetic distance analysis indicates that Amerindian and Australoid are genetically closer to Mongoloid than to Caucasoid and Negroid, as expected. It is indicated that the evolutionary mechanism of ethnic differences in reaction to drugs and food should be studied with the knowledge that different groups of human populations have been separated for a long time in the evolutionary process. The geographic distributions of the genes for lactose absorption and aldehyde dehydrogenase-I isozyme deficiency suggest that they have existed for a very long time in human populations and that genetic drift has been an important factor in the geographic differentiation of the frequencies of these genes. By contrast, the variant alleles at the pseudocholinesterase locus seem to be maintained by the balance between mutation and weak selection.