.png){kind=icon}
Chapter Summary
This chapter begins with an analysis of the scientific contributions of neo-Darwinians, who synthesized ideas about natural selection with Mendel’s ideas about heredity. Neo-Darwinians studied populations of reproductively isolated species, concentrating on the population’s gene pool, estimating the frequency of occurrence of different alleles of a particular gene, and predicting how gene frequencies are affected by different selection pressures.
Human population genetics has shown that different human populations share the same range of genotypic variation, no matter how different they may appear phenotypically. This reinforces the position that the concept of “race” is biologically meaningless. In particular, natural selection seems to have molded many complex human phenotypic traits, better adapting human populations to their environments. Anthropologists have studied how variations in traits such as skin colour appear to have been shaped by natural selection. Anthropologists have also shown how variations in IQ test scores reflect variations in cultural background, social class, and educational background rather than “race.”
Natural selection, mutation, gene flow, and genetic drift are four evolutionary processes that can affect change in gene frequencies in a population over time. Sometimes one evolutionary process may work to increase the frequency of a particular allele while a different process is working to decrease its frequency. Inbreeding over several generations can be harmful because it decreases genetic variation and increases the probability that any alleles for deleterious traits will be inherited in a double dose, one from each parent.
Gene-centered explanations of human evolution gained influence in anthropology after 1975 because of the widespread impact of a school of evolutionary thought called “sociobiology.” Sociobiologists have used formal mathematical models borrowed from population genetics and game theory to back up some of their claims. Anthropologists have been involved in the development of formal models critical of sociobiological models. The most influential critical models include those of gene–culture coevolution, cultural group selection, and niche construction. All of these perspectives have served to help in our examination of the future of human evolution is a mix of nature and nurture and that the search for meaningful existence, along with biological needs, underpins our challenge for the future.
Learning Objectives
In this chapter, the student should learn to do the following:
- understand and explain the differences between microevolution and macroevolution;
- outline and explain the four main evolutionary processes;
- explain some of the problems associated with sociobiological explanations of human behaviour and how anthropological explanations often challenge sociobiology;
- explain the limitations of natural selection and genetic variation for explaining human adaptations in various parts of the world;
- discuss how projects like the human genome project challenge the supposed “naturalness” of race.