古DNA的新发现支持现代人东亚起源说

1983年,科学家们根据线粒体DNA（mtDNA）系统发育树构建了首个现代人起源的分子模型,认为现代人起源于亚洲,但1987年非洲起源说的提出取代了这一亚洲起源说。非洲起源说所依赖的无限多位点假说以及分子钟假说后来被普遍认为是错误的且不切实际的。我们近几年提出了一个新的分子进化模式,即遗传多样性上限理论,重新构建了一个新的人类起源模型。这一模型与多地区起源说基本吻合, 重新把现代人类起源地定位在了东亚。非洲说与东亚说在线粒体进化树上的主要区别是单倍型N和R的关系,非洲起源说认为N是R的祖先,东亚说则反之。本研究引用了已发表的古代人群mtDNA数据,重点分析了线粒体单倍群N和R的关系。结果显示,三个最古老的人类（一个距今45000年,其他两个约40000年）都属于单倍群R;在距今39500到30000年前的人类样本中,绝大部分属于单倍群R下游的亚单倍群U,只有两例为单倍群N（Oase1距今39500年,Salkhit距今34425年）。这两例所属单倍型位于单倍群N下游最基本的未分化亚型,不属于今天存在的任何N下游单倍型,所以可能靠近单倍群N的根部。这些古DNA数据揭示单倍群R比单倍群N古老大约5000年,进一步证实了亚洲起源说的正确性,非洲说的依据不足。

The Out of East Asia theory of modern human origins supported by recent ancient mtDNA findings

It was in 1983 that scientists constructed the first molecular model of modern human origin based on the mitochondrial DNA (mtDNA) phylogenetic tree, and concluded that modern people originated in Asia. However, in 1987, the Out of Africa model also known as African Eve model was proposed and replaced the original model. But the infinite site assumption and the molecular clock hypothesis on which the African Eve model was based have been widely considered to be unrealistic. In recent years, we have proposed a new molecular evolution theory, namely the maximum genetic diversity(MGD) theory, and used it to reconstruct a new model of human origin, which is basically consistent with the Multiregional model and has the root of modern humans in East Asia. The main difference between the African Eve and our Asia model in the mtDNA tree is the relationship between haplotypes N and R. The African Eve model says that N is the ancestor of R, and our model indicates it is the opposite. In this research, we studied those mtDNA data published from ancient samples, focusing on the relationship between mitochondrial haplogroup N and R. The results show that the three oldest humans (one from 45,000 years ago and the other two about 40,000 years) belong to the haplogroup R. In the human samples from 39,500 to 30,000 years ago, most of them belong to the sub-haplogroup U downstream of the haplogroup R, and only two of them fall into the haplogroup N group(Oase1 is 39,500 years ago, Salkhit is 34,426 years ago). The haplotypes of these two individuals are not part of any prensent N downstream haplotypes and so may be close to the roots of the haplogroup N. These ancient DNA data reveal that the haplogroup R is about 5,000 years older than the haplogroup N, thus confirming the East Asia model and invalidating the African Eve model.