REVIEWS OALESCENCE del fails to explain the haplotype data from million year pedigree-like network in Chromosomes. As discussed above, evidence from Y- only reflect the difference in the effective population sampled are united under a e biallelic markers seems to be consister sizes between y chromosome/mtDNA and X chromo- nly under the Out-of-Africa model, as all of the East some/autosome(3-4 times greater in the latter)in bot- Asian haplotypes are regionally specific, are derived tleneck events that were associated with the outbound from a small number of African ancestors and show no migrations from Africa". That is, the coALESCENCE of ancient local contributions. In particular, all the muta autosome and X chromosome DNA sequences may tions found outside Africa are less than 50,000 years old precede the divergence between Africans and non and were derived from Africa. However, if extensive Africans. In other words, the age estimates based on X gene flow had occurred between continental popula- chromosomal and autosomal regions are compatible tions during the past one million years, the ancient Y- with both competing hypotheses; therefore, those chromosome haplotypes seen in African populations, above are not useful statistics to distinguish between or even much older haplotypes, would also be expected the two competing models. in East Asia, which seems not to be the case The second argument raised by multiregionalists The only remaining genetic evidence that seems to comes from archaeological findings in East Asia, espe irreconcilable with the Out-of-Africa hypothesis cially in China. As already mentioned, a continuous comes from several studies on autosomal and X-chro- evolutionary chain has been proposed to connect H. mosomal genes -3.The common ancestor of these erectus to H. sapiensin China, and this was used to sup- genes is estimated to have originated 535,000 to port either an independent origin of modern humans 1,860,000 years ago. This is much older than the age in East Asia or the trellis model 2. However, close estimates for mtdna and y chromosomes and has examination of the collection of hominid fossils in been considered to favour a multiregional origin. a China revealed a non-trivial temporal gap between recent study on a 10-kilobase non-coding region of archaic humans(H sapiens) and modern humans(Hs chromosome 22 gave a similar estimate(about 1. 29 sapiens)(BOX 3). All the H sapiens fossils are at least ①=mc Korean Taiwanese Malaysian -H12 Figure 2 The distribution of the seven East Asian-specific Y-chromosome haplotypes. Northern populations are indicated in red text and southern populations in black text. The Yangtze River divides the northern and southern populations Tibetans are an exception and are classified as northern on the basis of their history. In general, the seven East Asian-specific Y-chromosome haplotypes(H6-H12)represent most East Asian Y chromosomes and support a common African origin(FIG. 1) Mainland Southeast Asia is probably the first settlement of modern humans from Africa, as reflected by the presence of almost NATURE REVIEWS GENETIC VOLUME 1 NOVEMBER 2000129 M@ 2000 Macmillan Magazines LtdNATURE REVIEWS | GENETICS VOLUME 1 | NOVEMBER 2000 | 129 REVIEWS million years)43. This difference in age estimates might only reflect the difference in the effective population sizes between Y chromosome/mtDNA and X chromo￾some/autosome (3–4 times greater in the latter) in bot￾tleneck events that were associated with the outbound migrations from Africa44. That is, the COALESCENCE of autosome and X chromosome DNA sequences may precede the divergence between Africans and non￾Africans. In other words, the age estimates based on X￾chromosomal and autosomal regions are compatible with both competing hypotheses; therefore, those above are not useful statistics to distinguish between the two competing models. The second argument raised by multiregionalists comes from archaeological findings in East Asia, espe￾cially in China. As already mentioned, a continuous evolutionary chain has been proposed to connect H. erectus to H. sapiens in China, and this was used to sup￾port either an independent origin of modern humans in East Asia or the trellis model11,12. However, close examination of the collection of hominid fossils in China revealed a non-trivial temporal gap between archaic humans (H. sapiens) and modern humans (H. s. sapiens) (BOX 3). All the H. sapiens fossils are at least the trellis model fails to explain the haplotype data from Y chromosomes. As discussed above, evidence from Y￾chromosome biallelic markers seems to be consistent only under the Out-of-Africa model, as all of the East Asian haplotypes are regionally specific, are derived from a small number of African ancestors and show no ancient local contributions. In particular, all the muta￾tions found outside Africa are less than 50,000 years old and were derived from Africa40. However, if extensive gene flow had occurred between continental popula￾tions during the past one million years, the ancient Y￾chromosome haplotypes seen in African populations, or even much older haplotypes, would also be expected in East Asia, which seems not to be the case. The only remaining genetic evidence that seems to be irreconcilable with the Out-of-Africa hypothesis comes from several studies on autosomal and X-chro￾mosomal genes31–33. The common ancestor of these genes is estimated to have originated 535,000 to 1,860,000 years ago. This is much older than the age estimates for mtDNA and Y chromosomes, and has been considered to favour a multiregional origin. A recent study on a 10-kilobase non-coding region of chromosome 22 gave a similar estimate (about 1.29 Buryat Manchurian Mongolian Korean Japanese Hui Tibetan Tujia Yao Zhuang Dong Lahu Yi She Li Cambodian Dai Tu Sala Northern Han Southern Han Baric Thai Malaysian Taiwanese Indonesian Micronesian Polynesian =H6 =H7 =H8 =H9 =H10 =H11 =H12 =Others Figure 2 | The distribution of the seven East Asian-specific Y-chromosome haplotypes. Northern populations are indicated in red text and southern populations in black text. The Yangtze River divides the northern and southern populations. Tibetans are an exception and are classified as northern on the basis of their history. In general, the seven East Asian-specific Y-chromosome haplotypes (H6–H12) represent most East Asian Y chromosomes and support a common African origin (FIG. 1). Mainland Southeast Asia is probably the first settlement of modern humans from Africa, as reflected by the presence of almost all seven haplotypes in Thai and Cambodian populations. COALESCENCE A pedigree-like network in which all living individuals sampled are united under a most recent common ancestor. © 2000 Macmillan Magazines Ltd