Science

Western China’s mysterious mummies were local descendants of ice age ancestors

The Tarim Basin mummies have been a mystery ever since European explorers discovered them in northwestern China in the early 20th century. They were tall, wore wool felt hats and leather booties, and some had fair hair—all suggesting they were strangers from a strange land.

But a new study of the mummies’ DNA finds they were locals with deep roots in the region. Indeed, they appear to be relics of an ancient population that disappeared in Eurasia after the last ice age—one that was ancestral to Indigenous peoples living in Siberia and the Americas today.

It’s “fantastic” to learn that these mummies were local Asians, says Alison Betts, an archaeologist of Scottish descent at the University of Sydney who was not involved with the work. “Honest to God, one looks like my granny, with her very elegant bone structure … and her legs in woolen leggings, with blue and orange wrapping and boots like Uggs.”

Anthropologists have floated many theories about the Tarim Basin mummies. One is that they were descendants of the Yamnaya and Afanasievo nomadic herders from the steppes of the Black Sea region of Russia, because of their unusual height, woven woolen clothing, and cattle-centric culture. (The mummies were found in wooden boats covered with cow hides and adorned with horned cow skulls.) Another hypothesis is that they descend from farmers who migrated from desert oases of Bactria, or what is now modern Afghanistan, Turkmenistan, and Uzbekistan, based on similarities of agricultural and irrigation systems. Both ideas suggest these people brought Tocharian, an extinct branch of Indo-European languages, to the region.

To test these hypotheses, molecular anthropologist Yinqiu Cui of Jilin University organized an international team to analyze the DNA across the genomes of 13 of the oldest mummies found at sites such as Xiaohe and Gumugou in the Tarim Basin, dating from 4100 to 3700 years ago. Population geneticist Choongwon Jeong of Seoul National University compared their DNA with that of five even earlier individuals dating to 5000 to 4800 years ago in the neighboring Dzungarian Basin, and with other ancient and living Eurasians, in the first genomic study of prehistoric populations in the region.

Much to the scientists’ surprise, the mummies were most closely related to a previously identified genetic group called the Ancient North Eurasians, a once widespread population of hunter-gatherers that had greatly declined by the end of the last ice age. Researchers have wondered what happened to these people, but it is “totally unexpected” to find them in the Tarim Basin in the early Bronze Age, Jeong says. Today, this population survives only fractionally in the genomes of living people, with Indigenous populations in Siberia and the Americas having the highest proportions.

Mummies were found buried in wooden boats with oars, which were covered with cowhides at this ancient cemetery at Xiaohe in the Tamir Basin. Wenying Li/Xinjiang Institute of Cultural Relics and Archaeology

The mummies were remarkably similar genetically, the team reports today in Nature. The DNA from individuals 400 kilometers apart on opposite ends of the Tarim Basin was as similar as that from siblings. Even though the mummies were locals who didn’t intermarry with the migrant herders in nearby mountain valleys, they weren’t culturally isolated. By 4000 years ago, they had already adopted new ideas and culture: They wore woven woolen clothing, built irrigation systems, grew nonnative wheat and millet, and herded sheep and goats, as well as milking cattle to make cheese.

“The Bronze Age people of the Tarim Basin were genetically isolated but culturally incredibly cosmopolitan,” says study co-author Christina Warinner, a molecular archeologist at Harvard University and the Max Planck Institute for Evolutionary Anthropology.

“It’s superexciting” to see evidence that new ideas, technology, and culture spread between different cultures before their genes or languages spread, says Michael Frachetti, an archaeologist at Washington University in St. Louis who was not part of the study. “It speaks to the vast trade networks that spread even to these people, isolated in the desert.”

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