Chapter Summary

While a major focus of bioanthropology is on the evolutionary history of the hominids, the study of the current product of that evolution—modern Homo sapiens—is also important. We study living populations of our species from several different yet interrelated approaches.

If we know the genetic mechanism for a particular phenotypic trait, we can calculate the frequencies of the alleles of the gene involved and then see what changes in allele frequency take place in populations over time. Since evolution is technically defined as change in allele frequency, this allows us to see if evolution is in operation for that phenotype and to try to determine what processes of evolution are involved. The use of the Hardy-Weinberg equilibrium lets us make this analysis even if we cannot examine a population at several different time periods.

Even if we don’t know the genetic mechanism of a trait, we may still use that trait to study processes of evolution, provided it is under some genetic control. By statistically comparing populations, or groups within a population, for such a trait, we may estimate their genetic distances. In this way, we can hypothesize what sorts of evolutionary changes are taking place. Now, of course, we may compare individuals and populations at the most specific genetic level, the sequence of base pairs in the DNA. When we analyze such data, we see that the biology of demographic changes is intimately linked to cultural variables of the studied populations.

Since humans live in such a wide range of environmental circumstances, it stands to reason that human groups would have different adaptations to those environments. Most adaptations of our species are cultural, but we still exhibit a number of variable traits based on genetic polymorphisms. There is evidence that our variation in these traits is the result of natural selection at some point in our evolution to climatic and other environmental variables.

Among the environmental factors to which humans respond evolutionarily are diseases. Many diseases are caused by or carried by other species, so evolutionary theory may be applied to our understanding of their epidemiology. Viewed from this perspective, we may see some general trends in the relationship between our species and other disease causing species, in the past and in the present.

Finally, we understand that we need to study not only adult members of our species but also the growth and development of immature members, who are in the process of becoming adults. The timing of certain changes and the pace at which they occur are part of our species’ characteristics. Understanding how these changes and rates of change differ from those of other species is beginning to shed more light on the nature and course of our evolution.

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