Book reviews

During the twentieth century various biological disciplines tried to reconstruct and understand the origin and past history of modern humans. For anthropologists and human geneticists the study of microevolution, i.e. the factors affecting the variation of gene frequency patterns, has been the major field of investigation. In the early thirties, Fisher developed a systematic theory of evolution by natural selection and predicted that in a large population even slight selective differentials could replace a less advantageous twentieth with a more favoured one. At the same time Wright also developed a general theory of evolution and his argument was based on the fact that a species is composed of many small and nearly isolated subpopulations and within most there exist some boundaries to breeding. The size of these isolates is very important in the evolutionary process and assuming the population is randomly mating and there is no selection or mutation, such subdivisions will show genetic differentiation as a result of chance processes. When the isolation is partial the rate of divergence will depend on the amount of migration or gene flow. Gene flow between subpopulations retards the process of genetic differentiation. It is obvious therefore that in addition to conventional genetic factors, an understanding of demography, ecology, environment of the natural habitat, social behaviours and all other factors which promote migration and colonization are very important for understanding present day population structure. Since extensive information was available from historical records of the social and demographic structure of the human population, this led to the development of many classical models of population structure. More recently computer-intensive simulation methods have been developed which allow the study of migration and its effects through time, during the microevolution of humans.