Partial male genealogies showing inconsistencies in the transmission of Y chromosome haplotypes in five of the seven families on Tristan da Cunha. To conceal the identities of the families, only partial sib-ships are shown without indicating the generations in the pedigrees. Not all the males from whom Y chromosome data were obtained are presented. Tested individuals are indicated by filled squares. (a) Partial genealogy of family 3. An additional haplotype was found in four individuals spanning three generations. This haplotype most likely evolved from the haplotype associated with family 3 due to a single-step microsatellite mutation at DYS391. Arrow indicates the individual in whom the mutation probably originated. (b) Partial genealogy of family 4. The additional haplotype has a non-island origin (see Table 1). (c) Partial genealogy of family 5. The additional haplotypes observed in two branches of the genealogy are identical to the haplotype of family 7. (d) Partial genealogy of family 6. The additional haplotype in one branch of the genealogy is identical to the haplotype associated with family 5. (e) Partial genealogy of family 7. The additional haplotype is identical to the haplotype associated with family 5.