Serum samples from 526 baboons (Papio cynocephalus) from 10 troops from the Laikipia district of northern Kenya, from 60 baboons from two troops from the Awash National Park, central Ethiopia, and from 127 baboons from South Africa were tested for Gm and Inv allotypes. Four of the 10 troops from Kenya formed a western cluster and six formed an eastern cluster. The clusters were separated by approximately 10 miles.The samples were tested for Gm (1,2,3,5,6,11, 13,14,15, 16,17,21,24) and for Inv (1, 2, 3). All samples were negative for Gm (2, 6, 14, 16, 24). All from Kenya and Ethiopia were negative for Inv (2), and all were positive for Gm (11, 17) and for Inv (3). The south African samples differed from the others in that 10 were negative for Gm (11) and four were positive for Inv (2). Taking all animals into account, polymorphism was present for Gm (1, 3,5, 11, 13, 15, 21) and for Inv (1, 2). No two Kenya troops had the same array of phenotypes or of haplotypes, but the four western troops were more similar to each other than to the six eastern troops. Three haplotypes were present in the eastern troops that were not present in the western troops and five were present in the western troops that were not present in the eastern troops. Five haplotypes appeared in a t least some troops of each cluster of troops. The samples from each of the two troops from Ethiopia show the same three phenotypes but with significantly different frequencies.It is suggested that the variation in haplotype frequencies observed among the 10 troops from Kenya is the result of a founder effect deriving largely from fission of a large troop into two smaller troops.The data show that speculations about the evolutionary origin of the allotypes are premature. For most species, too few animals have been tested and except for those in this study their origins are not known. Finally, the samples have been from too restricted an area.
