Genetic Genealogy & Ancient DNA (TITLES/ABSTRACTS)

[Riverman]

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Inferring the demographic history of Hexi Corridor over the past two millennia from ancient genomes

The Hexi Corridor in northwest China has for millennia served as a crossroads for interactions
between East Asia, Central Asia and lands further west, while also connecting the Chinese
heartland and the northern Mongolian Steppe and Tibetan Plateau (TP) to the south (Fig. 1a).
Previous studies have revealed the details of this cross-continental material and cultural
transmission as early as the Bronze Age onwards. Materials and technologies exchanged along the
ancient Silk Road included East Asian millets and painted pottery, West Asian wheat and barley,
bronze metallurgy, domesticated sheep, horses, and cattle [1]. To date, paleogenomic studies have
examined the genetic structure of the eastern Hexi Corridor [2] and neighboring populations, such
as northern China [2], the Western Regions (present-day Xinjiang) [3], Tibetan Plateau [4] and
Mongolia [5] for these formative Neolithic and Bronze Age periods. Uniparental or limited
autosomal studies have shed some light on demographic interactions in the east[2], center[6] and
far west[7] of the historical Hexi Corridor, and genome-wide single nucleotide polymorphisms
(SNPs) studies revealed the genetic landscape of western-eastern admixture pattern of the present-
day Hexi Corridor [8–10]. However, population dynamics in Hexi Corridor across a longer
tranche of time has been gravely under-represented. To address the limitations above, we sampled
and sequenced 30 ancient individuals across the Hexi Corridor (Fig. 1a, b and Table S1A online).
We sampled 17 human individuals from the Heishuiguo site from the central Hexi Corridor, dating
from the Western Han Dynasty (202 BC–8 AD) through the Eastern Han Dynasty (25–220 AD).
From the western Hexi Corridor, we sampled 13 human individuals from the Foyemiaowan
cemetery, dating from the Cao-Wei (220–265 AD) to the Tang dynasties (618–907 AD). To
establish the chronology of our study, we relied on both archaeological and radiocarbon dating
evidence. We list the detailed information of each sample in Table S1A (online)

When we used the Foyemiaowan/Heishuiguo/Dacaozi and western Eurasian-
related ancestry as sources in the well-fitted qpAdm models, we estimated that 10 out of 11 and 40
out of 41 admixture events occurred approximately 10–20 and 5–10 generations before the death
of Foyemiaowan_Cao-Wei_o and Foyemiaowan_Tang_o. These dates aligned closely with the
Warring States period (475/403–221 BC) to the Western Han Dynasty (220 BC–8 AD) and the
Eastern Jin (317–420 AD) to the Tang Dynasty (618–907 AD), respectively (Fig. S8b and Table
S3E online). The admixture dates of Foyemiaowan_Cao-Wei_o and Foyemiaowan_Tang_o
coincided with the Historical era, particularly the period following the reclaiming of the Hexi
Corridor and the establishment of the ancient Silk Road by the Han Empire. These findings
emphasize the significant role played by the Silk Road in facilitating genetic exchanges between
East and West.

Surprisingly, results showed an increased proportion of western Eurasian-related ancestry on the X
chromosome compared to autosomes in both Foyemiaowan_Cao-Wei_o and
Foyemiaowan_Tang_o (Fig. S8c and Table S3C online). These outlier individuals exhibited a
prominent female bias for western Eurasian-related ancestry. Interestingly, a similar pattern was
observed in the Khitan and Mongol empires [5]. However, a lack of archaeological and ancient
DNA studies on the sociocultural patterns (e.g., patrilocality or matrilocality; polygamy or
polyandry) in the historical Hexi Corridor hindered our ability to explain the female-biased
admixture with western Eurasian-related ancestry. However, historical documents, excavated
epitaphs, and Tang poetry [20] indicate that marriages between Han males and non-Han females
were common.

(iii) Western Eurasians account for ~5%–20% of the gene pool of present-day Hexi Corridor
ethnic groups. To quantify the genetic contribution of historical period Hexi Corridor-related
lineages to present-day ethnic groups residing in the Hexi Corridor, we reanalyzed published
genome-wide SNP data of present-day Gansu Han Chinese [8], Altaic-speaking Yugur, Baoan and
Dongxiang [9,10], who are indigenous in Gansu Province. In 2-way qpAdm modeling, we found
that Gansu ethnic groups possessed ~80%–95% historical period Hexi Corridor-related ancestry
(represented by Heishuiguo/Foyemiaowan/Dacaozi) and ~5%–20% western Eurasian-related
ancestry (Fig. 2c), while no significant sex-biased admixture pattern was observed within our
limited resolution (Fig. S10a–c, and Tables S4A–C and S5A–C online). According to our analysis
8
using present-day Han Chinese/Korean and Europeans/Inner Asians as sources (Fig. S10d, and
Tables S4D and S5D online), the admixture events for present-day Gansu ethnic groups, estimated
through ALDER, were dated to approximately 600–1000 years before the present, corresponding
to the Song and Yuan dynasties (960–1368 AD).

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