The Genetics of Human Populations

Abstract

THE science of human genetics concerns the material substance with which every human being starts his existence. This substance we know to be handed down to each individual through the cytoplasm and through the nucleus of the cells which contribute to his formation. As vet we do not know the total function of each of these two components of the cell, but apparently from a lhereditary point of view, the nucleus with its genes is the more important part. At least the science of human genetics of to-day is concerned primarily with the distribution and the function of human genes. A human individual may be thought of as an isolated unit which is completely independent of, all other units, except for the fact that it had its origin in other units, or it may be thought of as a component of a larger unit, the population. These two units, the individual organism and the population, have many points' in common. Both are integrated units made up of smaller components, and many of the functions of the components of one are similar to the functions of the components of the other. From a genetic point of view, however, the two units differ considerably. In the individual organism the conmponents or cells all have the same genes, whereas in the population the components or individual organisms all have, or at least may have different genes. Furthermore, in the individual organism the hereditary composition does not change during the lifetime of the unit, whereas in the population it is, or at least may be, continually changing. Because of these specific genetic differences, there appear to be certain advantages in subdividing the science of human genetics into: (1) the genetics of human individuals, and (2) the genetics of human populations.