 Figure 1. The interaction of Random Genetic Drift and Natural Selection. The strength of selection is measured by the selective effect, \(s\), of a single gene and the strength of random genetic drift is indicated by \((1/2N_e)\), where the population has effective size, \(N_e\). When \(s\) exceeds \((1/2N_e)\), then the evolutionary fate of a gene is determined primarily by Natural Selection. When \(s\) is less than \((1/2N_e)\), then the evolutionary fate of a gene is determined primarily by Random Genetic Drift. Thus, the evolutionary domains of natural selection (upper) and random genetic drift (lower) are separated by the wavy boundary determined by the effective population size. [An  extended description of figure 1  is in the supplement.]