Indirect estimates of mutation rates in tribal Amerindians

Three different formulations have been used to estimate the average rate/locus/generation with which mutation results in electrophoretically detectable variants of 28 proteins in 12 tribal Amerindian populations. All methods are indirect--i.e., they assume a reasonable approximation to equilibrium between mutation and loss of mutants from the population--and are based on the further assumption that the biochemical traits under consideration are essentially neutral in their phenotypic effects. Despite the fact that the methods draw on somewhat different aspects of the available data, there is satisfactory agreement between them, the average of the three estimates being 1.6 X 10(-5)/locus/generation. This average does not encompass mutation that does not result in a change in electrophoretic mobility or that results in loss of enzyme activity. It is noteworthy that this estimate is in satisfactory agreement with a recent estimate by Neel and Thompson [Neel, J. V. & Thompson, E. A. (1978) Proc. Natl. Acad. Sci. USA 75, 1904--1908] of the mutation pressure necessary to maintain the number of "private" genetic polymorphisms being encountered in Amerindian tribes, if selection is not a factor.