Analysis of the human Y-chromosome haplogroup Q characterizes ancient population movements in Eurasia and the Americas

Results

Our analyses of 1.5 Mb of 152 Y chromosomes, 34 re-sequenced in this work, support a “coastal and inland routes scenario” for the first entrance of modern humans in North America. We show a major phase of male population growth in the Americas after 15 thousand years ago (kya), followed by a period of constant population size from 8 to 3 kya, after which a secondary sign of growth was registered. The estimated dates of the first expansion in Mesoamerica and the Isthmo-Colombian Area, mainly revealed by haplogroup Q-Z780, suggest an entrance in South America prior to 15 kya. During the global constant population size phase, local South American hints of growth were registered by different Q-M848 sub-clades. These expansion events, which started during the Holocene with the improvement of climatic conditions, can be ascribed to multiple cultural changes rather than a steady population growth and a single cohesive culture diffusion as it occurred in Europe.


Conclusions

We established and dated a detailed haplogroup Q phylogeny that provides new insights into the geographic distribution of its Eurasian and American branches in modern and ancient samples.


背景

近期对现代和古代样本的基因组研究表明，美洲原住民起源于欧亚基因库的一个子集，该子集由祖先白令海峡人群携带至美洲。该子集由两个高度分化的组成部分组成，并在其向美洲扩张的过程中以不同的比例混合。为了评估这些组成部分的起源时间、地点和混合程度，我们对Y染色体单倍群Q进行了分析。Q是唯一一个泛美洲单倍群，几乎涵盖了中美洲和南美洲所有美洲原住民的Y染色体。


结果

我们对152条Y染色体（其中34条进行了重测序）的1.5 Mb数据进行了分析，结果支持现代人类首次进入北美的“沿海和内陆路线图”。我们发现，美洲男性人口在距今1.5万年前（kya）后经历了一个主要的增长阶段，随后在8万年前至3万年前经历了一段人口规模保持稳定的时期，此后出现了第二次增长迹象。中美洲和哥伦比亚地峡地区首次扩张的估计日期（主要由单倍群Q-Z780揭示）表明，该族群在距今1.5万年前之前就已进入南美洲。在全球人口规模保持稳定的阶段，不同的Q-M848亚支系记录了南美洲局部地区的增长迹象。这些扩张事件始于全新世，伴随气候条件的改善，可以归因于多重文化变迁，而非像欧洲那样，由稳定的人口增长和单一的、有凝聚力的文化传播所致。


结论

我们建立并测定了详细的单倍群Q系统发育史，为理解其在现代和古代样本中欧亚和美洲分支的地理分布提供了新的见解。