Epilogue: A Hypothesis on the East Asian Beginnings of the Yersinia pestis Polytomy

TL;DR

Hymes hypothesizes that the Yersinia pestis polytomy dated by Cui et al. to 1142–1339 can be historically located in the Mongols’ conquest of the Xia/Tangut state in the Gansu corridor and their subsequent expansion. He argues that Chinese epidemic records from 1211 onward, especially the 1232 Kaifeng outbreak, are compatible with plague and merit renewed research.

Key findings

• Cui et al. (2013) date the Y. pestis polytomy or “Big Bang” that yielded most current strains, including the 1348 Black Death strain, to between 1142 and 1339 at 95% confidence, with an origin in or near the Qinghai-Tibet Plateau; Hymes places this in the Mongols’ repeated attacks on and 1226–27 conquest of Xia, just north/northeast of the Qilian mountains.
• Chinese sources record new deadly epidemics in the years of the Mongol Xia conquest: a 1211 report of pestilence among Mongols in unfamiliar country; Li Gao’s reports of epidemics in Dongping, Taiyuan, Fengxiang, and other Jin cities between 1213 and 1222; and the 1232 Kaifeng siege epidemic, where Li Gao says about a million died and the Jin history says 900,000, with Kaifeng’s population at surrender the next year about 1.4 million and mortality “at least 40%.”
• Rhubarb appears twice as a treatment for these epidemics—Yelü Chucai in 1226 and Liu Fu/Chen Yizhong in 1273—which Hymes suggests may indirectly hint at raised sores, though he states no evidence unambiguously argues for plague.
• Population figures from Zhao and Xie place Song+Jin population in 1210 at just over 108 million, Yuan in 1292 at a bit more than 75 million, Yuan in 1351 at about 87 million, and Ming in 1381 at about 67 million; Cao Shuji lists 31 epidemics from 1297 through 1362, and Hymes notes six recorded epidemics in the north versus two in the south between 1211 and 1292, matching higher northern population loss.

Methods

• Essay/hypothesis synthesizing genetic findings from Cui et al. (2013) with historical documentary evidence and secondary scholarship, especially Cao Shuji (1995), McNeill, and Buell.
• Chronological textual analysis of Chinese sources on thirteenth- and fourteenth-century epidemics, including two sources Cao did not cite, comparing their timing and geography with Mongol campaigns and plague ecology.
• No new genetic or archaeological data are presented; the paper calls for future ancient-DNA and bioarchaeological work.

Limitations

• Stated: “No piece of evidence I offer argues unambiguously for plague”; Chinese sources have little to say about clinical symptoms and nothing about rodents, and the hypothesis may not be finally confirmable except by ancient-DNA evidence from thirteenth- and fourteenth-century Chinese and Central Asian bones or teeth.
• Stated: the author had only a quick review of Cao and Li (2006) and disagrees that the early Jin datou wen (“big-head epidemic”) is plague; further research is needed on Gansu rodents, marmot transport, and rhubarb.
• Evident: the argument is inferential and speculative, resting on fit between genetic timing/geography and brief, uneven, temporally distant historical records, with no direct pathogen evidence.