To investigate the genetic characteristics of the ancient populations of Hokkaido, northern Japan, polymorphisms of the ABO blood group gene were analyzed for 17 Jomon/Epi-Jomon specimens and 15 Okhotsk specimens using amplified product-length polymorphism and restriction fragment length polymorphism analyses. Five ABO alleles were identified from the Jomon/ Epi-Jomon and Okhotsk people. Allele frequencies of the Jomon/Epi-Jomon and Okhotsk people were compared with those of the modern Asian, European and Oceanic populations. The genetic relationships inferred from principal component analyses indicated that both Jomon/Epi-Jomon and Okhotsk people are included in the same group as modern Asian populations. However, the genetic characteristics of these ancient populations in Hokkaido were significantly different from each other, which is in agreement with the conclusions from mitochondrial DNA and ABCC11 gene analyses that were previously reported.

In order to investigate further the allele frequencies of the adenosine triphosphate-binding cassette sub-family C11 (ABCC11) gene, which determines earwax phenotypes, among ancient populations in Hokkaido, Japan, the single-nucleotide polymorphism and the 27 bp deletion in the ABCC11 gene were analyzed in ancient DNA extracted from 38 Epi-Jomon, 24 Jomon, and one Satsumon specimens excavated from various archaeological sites in Hokkaido. Of the specimens analyzed, 10 EpiJomon and three Jomon specimens were successfully genotyped. One homozygote for the 27 bp deletion was found first in one Epi-Jomon specimen. Including previously reported data on the Okhotsk people and modern Ainu, exact tests of population differentiation showed that allele frequencies of the ABCC11 gene between the Jomon people and Ainu were statistically significantly different, whereas those between the Jomon and Epi-Jomon people and those between the Epi-Jomon people and Ainu were not significantly different. This result indicates that the Ainu, direct descendants of the Jomon people, were genetically affected by populations who possessed high frequencies of allele A (recessive dry allele) of the ABCC11 locus after the Jomon period.