title: Measuring selection in human populations using the growth rate per generation.
abstract: Estimates of the speed of evolution between generations depend on the association between individual traits and a measure of fitness. The two most frequently used measures of fitness are the net reproduction rate and the 1-year growth factor implied by the fertility and mortality rates. Results based on the two lead to very different results. The reason is that the 1-year growth factor is not a measure of change between generations. Therefore, studies of changes between generations should use the amount of growth over the length of a generation. This is especially important for studies of human populations because of the long length of generation. In addition, estimates based on a single year's growth are overly sensitive to data on individuals who fail to reproduce. The effects of using a generational measure are demonstrated using data from Kenya and Ukraine. These results demonstrate that using a 1-year growth rate to measure fitness leads to estimates that understate the rate at which evolution changes the characteristics of a human population.
authors.affiliation: Population Studies Center, University of Pennsylvania, Philadelphia, PA 19104, USA ewbank@pop.upenn.edu.
authors.forename: Douglas
authors.initials: D
authors.lastname: Ewbank
mesh_terms: D005191:Family Characteristics; D005260:Female; D006801:Humans; D007630:Kenya; D008954:Models, Biological; D011158:Population Growth; D012098:Reproduction; D012641:Selection, Genetic; D014455:Ukraine
keywords: demography; evolution; humans; reproduction; selection