Collaborative Research: Genetic Variation Among Linguistically Divers Tanzanian Populations: Implications for East African History and Modern Human Origins

人类线粒体、常染色体和性染色体在撒哈拉以南非洲地区表现出相对较高的遗传多样性，反映了该地区人口历史、迁徙和细分的复杂模式，以及可能的现代人类起源。目前的挑战是更好地描述撒哈拉以南非洲地区的遗传多样性，并重建该地区复杂的人口历史。特别是东非，被认为是过去10万年人类迁徙出非洲的一个可能来源。然而，在遗传变异的研究中，这一地区的样本和代表性仍然不足。坦桑尼亚位于非洲的一个地区，在语言、文化、社会和遗传上都很复杂。在非洲，说这四种语言的人口彼此之间距离很近。此外，这些人口的生存方式多种多样。虽然他们一直是许多人种学、语言学和考古学研究的焦点，但在遗传水平上对坦桑尼亚人口的研究很少。Hadzabe和Sandawe这两个目前（或在最近的过去）主要以狩猎采集为生活方式的族群，在语言上是孤立的，他们的语言中包含了click辅音，对他们进行分类是一个挑战。人们对他们之间的关系知之甚少，也不知道他们与说不同语言、采用不同生存方式的邻近民族之间的关系，也不知道他们与说科伊桑语的南部非洲民族之间的关系。科伊桑语也说含有咔嗒辅音的语言，并被假设起源于东非。该研究项目的具体目标是描述Hadzabe、Sandawe和邻近人群的遗传变异特征；重建这些东非族群之间以及与南部非洲科瓦桑语族群之间的关系；并验证关于现代人类可能起源于东非的假设。本项目分为三个重叠的阶段。第一阶段包括收集坦桑尼亚中部Hadzabe、Sandawe和邻近人群的血液和/或颊细胞。第二阶段包括对第一阶段收集的样本进行DNA分离和分子分型。对常染色体、X染色体和y染色体上的标记进行基因分型，对mtDNA进行独立分析和单倍型分析。第三阶段包括探索性数据分析和假设检验，给出第二阶段产生的数据。收集的数据将在目前存在的更广泛的非洲和全球数据集的背景下进行分析，预计将有助于对撒哈拉以南非洲遗传多样性的一般认识，并有助于了解东非人口之间的古代和历史关系。此外，由于东非可能是非洲人口迁移的来源，这些数据将为非洲现代人类的起源和进化提供重要的新见解，并将使关于非洲现代人类全球传播的广泛假设的测试成为可能。

Human mitochondrial, autosomal, and sex chromosomes exhibit relatively high levels of genetic diversity within sub-Saharan Africa, reflecting complex patterns of population history, migration, and subdivision and possibly the origin of modern humans within this region. The current challenge is to better characterize the genetic diversity within sub-Saharan Africa and to reconstruct the complex demographic history of the region. East Africa, in particular, is thought to be a likely source of a human migration out of Africa within the last 100,000 years. This region, however, remains highly under-sampled and under-represented in studies of genetic variation. Tanzania occupies a region of Africa which is linguistically, culturally, sociologically, and genetically complex. Populations speaking languages representing all four of the linguistic super-families present in Africa are located in close proximity to one another. In addition, these populations practice a variety of subsistence methods. Although they have been the focus of many ethnographic, linguistic, and archaeological studies, Tanzanian populations have been studied very little at the genetic level. The Hadzabe and Sandawe, two populations that currently practice (or in the recent past have practiced) a predominantly hunter-gatherer lifestyle, are linguistic isolates whose languages contain click consonants and have been a challenge to classify. Little is known about their relationship to one another, to neighboring peoples who speak distinct languages and practice different subsistence methods, or to southern African Khoisan-speaking peoples who also speak languages containing click consonants and are hypothesized to have originated in East Africa. The specific goals of this research project are to characterize genetic variation in the Hadzabe, Sandawe, and neighboring populations; to reconstruct the relationship of these East African populations to one another and to southern African Khoisan-speaking populations; and to test hypotheses regarding the possible origin of modern humans in East Africa. This proposed project is divided into three overlapping phases. Phase I includes the collection of blood and/or buccal cells from the Hadzabe, Sandawe and neighboring populations in central Tanzania. Phase II consists of DNA isolation and molecular typing of the samples collected in Phase I. Samples will be genotyped for markers on autosomes, X- and Y-chromosomes, and mtDNA analyzed both independently and as haplotypes. Phase III includes exploratory data analysis and hypothesis testing given the data generated in phase II. The data collected will be analyzed within the context of a broader African and global data set that currently exists and is expected to contribute both to the general knowledge of genetic diversity within sub-Saharan Africa and to the understanding of ancient and historical relationships among East African populations. In addition, because East Africa is the likely source of populations migrating out of Africa, these data will provide important new insights into the origin and evolution of modern humans in Africa and will make possible the testing of a wide range of hypotheses concerning the global spread of modern humans out of Africa.