美洲祖先一部分来自中国？新研究：从中国北部沿海迁徙到美洲

据《卫报》5月9日报道，一项新的遗传学研究发现，古人类曾两次从中国“搬家”到美洲。

研究人员通过线粒体DNA（脱氧核糖核酸）样本研究，确定了两次发生在冰河时期的迁徙事件。在这两次事件中，来自今天中国北部沿海地区的早期人群沿着太平洋海岸迁徙到美洲。这为了解美洲原住民祖先起源增加了新的线索。

Some of the first humans to arrive in the Americas included people from what is now China, who arrived in two distinct migrations during and after the last ice age, a new genetics study has found.

《卫报》刊载的最新研究

这份研究发表在美国《细胞报告》杂志上。

人们此前主要认为，古西伯利亚人是美洲原住民的祖先。他们曾穿过白令海峡连接现代俄罗斯与阿拉斯加的一座大陆桥抵达美洲。

研究论文第一作者、中国科学院昆明动物研究所副研究员李玉春表示：“除了先前描述的西伯利亚、澳大利亚-美拉尼西亚和东南亚的祖先来源外，我们发现中国北部沿海地区人口也对美洲原住民的基因库有贡献。”

“Our findings indicate that besides the previously indicated ancestral sources of Native Americans in Siberia, the northern coastal China also served as a genetic reservoir contributing to the gene pool,” said Yu-Chun Li, one of the report authors.

为了揭示美洲原住民的亚洲历史，中科院昆明动物研究所等机构的研究人员追踪了一个古老人类谱系，即D4h。

D4h的谱系存在于线粒体DNA中，它只从母亲那里继承，因此可以用来追踪母系血统。

研究人员对D4h进行了长达10年的搜寻，梳理了欧亚大陆的10万份现代和1.5万份古代DNA样本。他们通过比较这些样本的累积基因突变、地理位置，并通过放射性碳技术测定年代，重建了D4h的起源和扩张历史。他们最终找到了216个当代个体和39个古代个体，他们均来自这个古代血统。

Known as D4h, this lineage is found in mitochondrial DNA, which is inherited only from mothers and is used to trace maternal ancestry.

The team from the Kunming Institute of Zoology embarked on a 10-year hunt for D4h, combing through 100,000 modern and 15,000 ancient DNA samples across Eurasia, eventually landing on 216 contemporary and 39 ancient individuals who came from the ancient lineage.

By analyzing the mutations that had accrued over time, looking at the samples' geographic locations and using carbon dating, they were able to reconstruct the D4h's origins and expansion history.

《细胞报告》刊载的最新研究

研究人员得以追踪到这一谱系的分支路径，确定了两次从今天中国北部沿海地区到达美洲的迁徙事件。

研究人员认为，第一次迁徙发生在距今26000年至19500年的末次盛冰期，当时冰盖覆盖面积最大，中国北方地区条件可能不适宜人类居住。

第二次发生在距今19000年至11500年的冰消期，可能由于气候条件改善，人口数量迅速增加，推动了这一地区人口向其他地区迁徙。

The results revealed two migration events. The first was between 19,500 and 26,000 years ago during the Last Glacial Maximum, when ice sheet coverage was at its greatest and climate conditions in northern China were probably inhospitable.

The second occurred during the melting period, between 19,000 and 11,500 years ago. Increasing human populations during this period might have triggered migrations.

正是在第二次迁徙期间，科学家们发现了美洲原住民和日本人，尤其是原住民阿伊努人之间惊人的遗传联系。

该研究称，在融化时期，一个亚群从中国北部沿海地区分支到了日本，这一发现与美洲、中国和日本古代人之间的考古学相似性相吻合。

It was during this second migration that the scientists found a surprising genetic link between Native Americans and Japanese people, particularly the indigenous Ainu.

In the melting period, a subgroup branched out from northern coastal China to Japan, contributing to the Japanese people, the study said, a finding that chimes with archeological similarities between ancient people in the Americas, China and Japan.

这一发现为解开美洲原住民起源之谜提供了新的线索。研究人员称，下一步他们将收集和调查更多来自欧亚大陆的遗传谱系，为破解谜团找出更多线索。

编辑：左卓

实习：智幸花

来源：新华社 极目新闻 卫报