Genetic evidence for the demic diffusion of agriculture to India
Genetic evidence for the demic diffusion of agriculture to India
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DOI：
10.1126/science.1095819
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发表时间：
2004-05-21
期刊：
影响因子：
56.9
通讯作者：
Stoneking, M
中科院分区：
文献类型：
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作者：
Cordaux, R;Deepa, E;Stoneking, M
农业在过去1万年里从新月沃地扩散的过程已经被广泛讨论，但至今没有达成共识：它主要是一种流行病扩散（人口的大规模扩散）还是一种文化扩散（没有大量的人口迁移）？流行扩散模型（1）预测了大量的遗传输入从迁移的农学家，而文化扩散模型（2）预测在遗传水平上没有重大变化。因此，测试这些相互竞争的假设的一种方法是比较传统农学家、传统狩猎采集者和现代农学家（即最近转向农业的前狩猎采集者）的遗传变异。在流行扩散模型下，现代农学家与传统农学家的遗传亲缘关系比狩猎采集者更近;而在文化扩散模型下，现代农学家在遗传上应该与狩猎采集者相似。对欧洲人的遗传研究得出了相互矛盾的结论，部分原因是农业化前欧洲人口的遗传组成是未知的。然而，在印度仍然存在非农业群体和最近采用农业的群体（3，4），允许农业传播的流行与文化传播模型的正式测试。种姓群体可以被认为是传统的农学家，因为他们引入了关键的创新（如铁技术），促进了农业向印度南部的扩展（4）。印度南部也有一些部落群体，他们通常被认为是该地区的土著居民，传统上是狩猎采集者（3，4）。他们中的一些人仍然通过狩猎和采集或非熟练劳动来生存，而其他人在过去的3000年里已经转向了农业主义的生存策略。遗传亲和力是从583名男性中分析的14个Y染色体单倍群的频率推断出来的，其中包括71名部落南印度狩猎采集者，60名部落南印度近代农学家，283名南印度和169名北印度传统农学家（5）。不同类别个体之间的成对遗传（Fst）距离表明，南印度近代农学家与传统农学家的关系比传统狩猎采集者的关系显着更密切（图1A）（对重叠Fst值进行检验，P 0.01）。这一结论得到了多维尺度分析的支持，该分析同时比较了所有四个类别;它还显示，与传统的狩猎采集者相比，最近的南印度农学家总体上在遗传上更类似于传统农学家（图1B）。遗传亲和力也是从632个个体的线粒体DNA（mtDNA）控制区序列中推导出来的，其中包括229个部落南印度狩猎采集者，201个部落南印度近代农学家，140个南印度和62个北印度传统农学家（5）。区分不同类别个体的成对Fst距离表明，与传统的狩猎采集者相比，南印度近代农学家与传统农学家的关系更为密切（图1A）（折形Fst值的t检验，P 0.001）。这一结论也得到了多维尺度分析的支持（图1C）;后者还表明，与传统的狩猎采集者相比，最近的南印度农学家在遗传上更接近传统农学家。因此，线粒体DNA变异的趋势，显着平行的Y染色体变异推断。这也反映在一个事实，即...
The process by which agriculture diffused from the Fertile Crescent within the past 10,000 years has been widely discussed, but as yet there is no consensus: Was it mostly a demic diffusion (with massive spread of people) or rather a cultural diffusion (without substantial migration of people)? The demic diffusion model (1) predicts a substantial genetic input from migrating agriculturalists, whereas the cultural diffusion model (2) predicts no major changes at the genetic level. Hence, a way to test these competing hypotheses would be to compare genetic variation in traditional agriculturalists, traditional huntergatherers, and recent agriculturalists (ie, former hunter-gatherers who recently shifted to agriculture). Under the demic diffusion model, recent agriculturalists are expected to show closer genetic affinities to traditional agriculturalists than do hunter-gatherers; whereas under the cultural diffusion model, recent agriculturalists should resemble hunter-gatherers genetically. Genetic studies of Europeans have led to conflicting conclusions, partly because the genetic composition of pre-agricultural European populations is unknown. However, there still exist in India both nonagricultural groups and groups that recently adopted agriculture (3, 4), allowing a formal test of the demic versus cultural diffusion models of the spread of agriculture. Caste groups can be considered as traditional agriculturalists in this context, because they introduced key innovations (such as iron technology) that facilitated the expansion of agriculture toward south India (4). There are also tribal groups in south India who are generally considered to be the aboriginal inhabitants of the region and who have traditionally been hunter-gatherers (3, 4). Some of them still survive through hunting and gathering or unskilled labor, whereas others have shifted to an agriculturalist subsistence strategy within the past 3000 years (4). Genetic affinities were deduced from the frequencies of 14 Y-chromosome haplogroups analyzed in 583 males, including 71 tribal south Indian hunter-gatherers, 60 tribal south Indian recent agriculturalists, and 283 south Indian and 169 north Indian traditional agriculturalists (5). Pairwise genetic (Fst) distances separating the different categories of individuals indicate that south Indian recent agriculturalists are significantly more closely related to traditional agriculturalists than are traditional hunter-gatherers (Fig. 1A)(ttest on jackknifed Fst values, P 0.01). This conclusion is supported by a multidimensional scaling analysis that simultaneously compared all four categories; it also reveals that recent south Indian agriculturalists are overall genetically more similar to traditional agriculturalists than to traditional hunter-gatherers (Fig. 1B). Genetic affinities were also deduced from sequences of the mitochondrial DNA (mtDNA) control region analyzed in 632 individuals, including 229 tribal south Indian hunter-gatherers, 201 tribal south Indian recent agriculturalists, and 140 south Indian and 62 north Indian traditional agriculturalists (5). Pairwise Fst distances separating the different categories of individuals indicate that south Indian recent agriculturalists are significantly more closely related to traditional agriculturalists than are traditional huntergatherers (Fig. 1A)(t test on jackknifed Fst values, P 0.001). This conclusion is also supported by a multidimensional scaling analysis (Fig. 1C); the latter also shows that recent south Indian agriculturalists are overall genetically more similar to traditional agriculturalists than to traditional huntergatherers. Thus, mtDNA variation shows trends that markedly parallel those deduced from Y-chromosome variation. This is also reflected in the fact that …