1722 Am.J.Hnm. Genet..65:1718-1724,1999 urred -18,000-25, 000 years ago. A similar dentition LALCACTTCTACGCCTWGG H3 ASCAGTITCACGCGTWGO w pattern predominates among all the Southeast Asian iCACTTTCACGCGTWGG ME populations and was thought to be ancestral to the Sino- L-sASCACTTICACGCGTWDG He dont pattern. Consequently, this sequence of dental ACGCETWGG H5 SASCCCTTTTACGCGTWGG h9 evolution tends to rule out an 18,000-year coloniza tion dating-the lower boundary of our age estima ASCACTITTACGTGTWGG tion- which was based on an overestimated effective 如 SASCACTTTTGCGTGTDGG H1 population size. In addition, archaeological evidence from the Altai Mountain and Lake Baikal regions of SASIACTTTAGACGTWGG MiS southeastern Siberia are beginning to show the presence SASCACTTTTACACGTWGD H of modern human lithic cultures of 25,000-45, 000 years SGSCACTTTTACGCGTWGG H1 ago(Vasil'ev 1993). Therefore, the first entry of eastern sian populations should predate the emergence of the hap. lithic culture in northern Asia. Recent evidence from lotypes in eastern-Asian and world populations. The letters"A, ""T, archaeological studies indicates that Papua New Guinea loci.The was settled -35,000-50,000 years ago by modern hu- letters"S"and "L"refer to small and large alleles, respectively. The mans, aboriginal Australia perhaps even earlier than that letters "W"and "D" refer to wild-type and deletion alleles, respec- (Brown et al. 1992: Swisher et al. 1996).Hence, if we each locus shown above the branches(for detailed descriptions of accept that mainland Southeast Asia is the homeland for mutations, see the Material and Methods section). all eastern-Asian populations, including Siberian and Oceanian, the upper boundary of the M122-lineage time depth-that is, 60,000 years agoseems to be a likely they expanded northward to other parts of eastern Asia. estimation of the initial colonization of eastern Asia by A study by Ballinger et al. (1992)also suggested a south- modern human populations from Africa ern Mongoloid origin of eastern Asians The last Ice Age occurred 75, 000-15,000 years ago To estimate the time of the entry of modern humans although its distribution and the exact date of its pres- nto eastern Asia, we typed three Y-chromosome micro- ence in eastern Asia are not clear(Dawson 1992). In- satellite loci for individuals carrying the C allele at locus M122-that is, the allele state shared by Asian-specific aplotypes H6-H8. a total of five, eight, and six alleles were observed at dyS391. DYS390. and DYS389. re- spectively. The single-step mutation model and a mu- tation rate of 0. 18%(Heyer et al. 1997; Bianchi et al Tibetan▲ Mongolian▲ Ewenki 1998)were used in the estimation. To minimize the pos- sible influence of population substructure on the esti- mation, only Han Chinese samples were included(160 O Lahu M122-C individuals in total). When an effective popu- lation size of 750-2, 000 is assumed(see the material Jao Northern-Han and Methods section), the number of generations esti- Paiwan mated is 919-3, 032 for DYS390, the oldest among all N Amio aTayal Malaysian Southern-Han three estimations. Therefore, the age of M122C is -18,000-60,000 years, if we assume a 20-year gener ation time. We argue that this estimation reflects the age odian o Dong of the bottleneck event leading to the entrance of modern o№ETha humans into eastern Asia, since the extensive presence of the M122-C allele in Southeast Asian populations suggests that this mutation predates their entry It is difficult to accurately date the ancient human migrations(or mutations), because of the errors inher ently involved in estimating both the effective population size of the males and the mutation rate. However, our knowledge of morphology and archaeology can help us ure to narrow the estimated age range. According to the lotype frequencies of 30 eastern-Asian populations. The geographic locations of the populations are shown in figure 1. The triangles refer morphological study by Turner et al. (1993), the so- to northern populations; the circles, to southern populations. This map called Sinodont dentition in northern-Asian peoples oc- accounts for 44% of the original genetic variation1722 Am. J. Hum. Genet. 65:1718–1724, 1999 Figure 2 Most parsimonious tree of the 17 Y-chromosome hap￾lotypes in eastern-Asian and world populations. The letters “A,” “T,” “G,” and “C” refer to the sequences of those polymorphic loci. The letters “S” and “L” refer to small and large alleles, respectively. The letters “W” and “D” refer to wild-type and deletion alleles, respec￾tively. The underlined letters indicate that the mutations occurred at each locus shown above the branches (for detailed descriptions of mutations, see the Material and Methods section). Figure 3 Principal-component analysis of Y-chromosome hap￾lotype frequencies of 30 eastern-Asian populations. The geographic locations of the populations are shown in figure 1. The triangles refer to northern populations; the circles, to southern populations. This map accounts for 44% of the original genetic variation. they expanded northward to other parts of eastern Asia. A study by Ballinger et al. (1992) also suggested a south￾ern Mongoloid origin of eastern Asians. To estimate the time of the entry of modern humans into eastern Asia, we typed three Y-chromosome micro￾satellite loci for individuals carrying the C allele at locus M122—that is, the allele state shared by Asian-specific haplotypes H6–H8. A total of five, eight, and six alleles were observed at DYS391, DYS390, and DYS389, re￾spectively. The single-step mutation model and a mu￾tation rate of 0.18% (Heyer et al. 1997; Bianchi et al. 1998) were used in the estimation. To minimize the pos￾sible influence of population substructure on the esti￾mation, only Han Chinese samples were included (160 M122-C individuals in total). When an effective popu￾lation size of 750–2,000 is assumed (see the Material and Methods section), the number of generations esti￾mated is 919–3,032 for DYS390, the oldest among all three estimations. Therefore, the age of M122C is ∼18,000–60,000 years, if we assume a 20-year gener￾ation time. We argue that this estimation reflects the age of the bottleneck event leading to the entrance of modern humans into eastern Asia, since the extensive presence of the M122-C allele in Southeast Asian populations suggests that this mutation predates their entry. It is difficult to accurately date the ancient human migrations (or mutations), because of the errors inher￾ently involved in estimating both the effective population size of the males and the mutation rate. However, our knowledge of morphology and archaeology can help us to narrow the estimated age range. According to the morphological study by Turner et al. (1993), the so￾called Sinodont dentition in northern-Asian peoples oc￾curred ∼18,000–25,000 years ago. A similar dentition pattern predominates among all the Southeast Asian populations and was thought to be ancestral to the Sino￾dont pattern. Consequently, this sequence of dental evolution tends to rule out an 18,000-year coloniza￾tion dating—the lower boundary of our age estima￾tion—which was based on an overestimated effective population size. In addition, archaeological evidence from the Altai Mountain and Lake Baikal regions of southeastern Siberia are beginning to show the presence of modern human lithic cultures of 25,000–45,000 years ago (Vasil’ev 1993). Therefore, the first entry of eastern￾Asian populations should predate the emergence of the lithic culture in northern Asia. Recent evidence from archaeological studies indicates that Papua New Guinea was settled ∼35,000–50,000 years ago by modern hu￾mans, aboriginal Australia perhaps even earlierthan that (Brown et al. 1992; Swisher et al. 1996). Hence, if we accept that mainland Southeast Asia is the homeland for all eastern-Asian populations, including Siberian and Oceanian, the upper boundary of the M122-lineage time depth—that is, 60,000 years ago—seems to be a likely estimation of the initial colonization of eastern Asia by modern human populations from Africa. The last Ice Age occurred 75,000–15,000 years ago, although its distribution and the exact date of its pres￾ence in eastern Asia are not clear (Dawson 1992). In-