The mtDNA Genetic Diversity Of 19 Individuals From Yíng Zhèng’s Terra Cotta Army Mausoleum

We know that during the Sui dynasty, the Chinese empire had European residents. But what can be said about the diversity of China during a preceding dynasty, such as Qin Shi Huang’s empire — the Qin dynasty of China? A team of Chinese academics have analyzed the mtDNA of 19 individuals excavated from a nearby tomb at the Terra Cotta Army site. They have published their study in the open access journal PLoS One under the title, “Mitochondrial DNA Evidence for a Diversified Origin of Workers Building Mausoleum for First Emperor of China.”

The Terra Cotta Army Site in China
The Terra Cotta Army Site in China

The remains date to 2,200 years ago, right around the time that Qin Shi Huang or Yíng Zhèng, was undertaking his massive project like building the Great Wall and the giant Terra Cotta warrior mausoleum. Yíng Zhèng is known for doing some great things for China. For example, he built an intricate road system which connected the twenty-two million inhabitants at the time and allowed him to control and unify such a vast territory. However, with such power came some questionable political measures. Zhèng buried alive many Confucian scholars and burned their books. And his large projects came at the expense of many people’s lives.

Although 121 skeletons were excavated from the Terra Cotta Army site, only 50 were genetically analyzed for this study, 19 of which yielded results. But based on morphological observations, all of them were robust and had signs of arthritis. Some had broken bones or signs of extensive muscular stress. All of this suggests that these people were engaged in heavy work before death… most likely slaves of the Emperor, forced to work on building such a massive mausoleum.

Razib raised issue that such ancient DNA analysis is subject to contamination, especially when trying to assess the genetic diversity of an ancient populations. But the authors seemed to have done the same ancient DNA song and dance that we’ve seen in the last year. They removed the outer layer of bone which was presumably handled under non sterile conditions. The bone was subject to UV radiation and chemical treatment to further nuke any exogenous DNA.

The extracted DNA was amplified via PCR with overlapping primers and TA sub-cloned. The samples were sequenced via the standard dideoxy-chain terminated method. Another independent lab preformed the same steps to replicate results and ensure contamination wasn’t much of an issue.

The ancient sequences were compared to 2,164 mtDNA profiles from 32 different Chinese populations. That was done to establish the geographic locations and ethnic affiliation of these ancient peoples to their modern contemporaries. Using the same primers, the mitochondrial genomes of all staff members that handled the remains, were also sequenced and compared. Because of the high amount of genetic diversity present in the results of the ancient DNA, and the high amount of homogeneity of the modern staff members’ mtDNA, the authors ruled out contamination from handling as a major issue.

Specifically, the 19 individuals came from 15 distinct east-Eurasia haplogroups. Overall, 4 of them were of Han origin. While 7 of them came from southern China. Three others came from minority groups in the south. Interestingly, one of these ancient workers carried the same variation in the haplogroup M7a seen in Ryukyuan and Japanese people.

Of course, as Razib mentioned, this sample size is small — only 19 of the assumed 720,000 workers it took to construct the mausoleum but this shows us that Yíng Zhèng recruited people from all over to work on his project. Is this surprising? No! It isn’t. We’re talking about an empire. Empires are huge, some span entire continents and are made up of many different elasticities. Other contemporaneous empires, such as the Romans and Persians, even the Egyptians, were hardly homogeneous. Why would the Qin Empire be otherwise? Especially under the control of the unifier, Yíng Zhèng, who pushed for the infastructure that connected China at the time.

    Zhi Xu, Fan Zhang, Bosong Xu, Jingze Tan, Shilin Li, Chunxiang Li, Hui Zhou, Hong Zhu, Jun Zhang, Qingbo Duan, Li Jin, Vincent Macaulay (2008). Mitochondrial DNA Evidence for a Diversified Origin of Workers Building Mausoleum for First Emperor of China PLoS ONE, 3 (10) DOI: 10.1371/journal.pone.0003275

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