Frequency of spontaneous and induced "point" mutations in higher eukaryotes

Data are presented on comparative mutation rates in Drosophila, mice, and humans, as derived from the study of both biochemical and morphological traits. There is a notable similarity in these rates, despite the large differences in average generation time, mean body temperature, and number of cell divisions intervening between fertilization of the egg and production of functional gametes. This suggests the evolution of superior genetic (DNA) repair strategies in (long-lived) humans. Evidence is reviewed that raises the possibility of higher mutation rates in mostly tropical-dwelling, tribal human populations than in temperate-dwelling civilized groups. The data suggesting that humans may be somewhat less sensitive to the genetic effects of radiation than mice are presented, and the question of whether this apparent difference is real or spurious is discussed. Finally, some possible new directions in the study of the mutation-selection balance are presented.