ABSTRACT
Physiological data from a range of human populations living in different environments can provide valuable information for testing evolutionary hypotheses about human adaptation. The comparative method can help us determine whether variation results from selection due to environmental factors, or is possibly selected for by cultural forces (which means that gene-culture coevolution is occurring). However, a simple, statistical correlation between traits across cultures is complicated by the non-independence of cultures, as was first recognised in the 19th century by Francis Galton. The same problem applies in cross-species comparisons. Evolutionary biologists have developed phylogenetic comparative methods that can take account of the hierarchical interrelatedness of species and test for the co-evolution of traits on phylogenetic trees. Mace and Pagel (1994) argued that similar approaches can be used to test cross-cultural hypotheses. In this chapter, we will outline an example of the use of one of these approaches to test adaptive hypotheses explaining global variation in population sex ratio at birth.
