Ancient texts have given rise to speculation he died from poison – either accidentally through taking toxic substances as an elixir or deliberately at the hands of an enemy.
This theory received some backing after his bones were rediscovered in 1996 and were later found to contain a larger than normal amount of arsenic, news portal The Paper reported last month. His femur also showed evidence of poisoning-related necrosis.
However, a thorough analysis of the emperor’s DNA obtained from his limb bones by a team led by researchers from Fudan University raises an alternative theory. The new analysis, published last week in the journal Current Biology, suggests he may have had an “increased susceptibility” to stroke.
The team also cited the Book of Zhou, an official history of the dynasty, which said that before his death he exhibited symptoms such as drooping eyelids, blindness and an abnormal gait – all possible symptoms of a stroke.
Forensic reconstruction, based on scanning facial bones to work out what someone looked like, can now be combined with DNA analysis to determine a person’s facial structure and genetic features such as their skin and eye colour.
Reconstructing the appearance of Emperor Wu and identifying his cause of death has long been a point of fascination for historians, archaeologists and anthropologists due to his important role in unifying northern China, the team said.
When the researchers began to examine Emperor Wu’s bones using traditional methods, they found that it was not enough to determine his genetic features.
The 100,000 genetic loci – locations on a chromosome associated with a specific gene – that the team obtained after six years’ research fell short of allowing the team to reconstruct the emperor’s face and medical risk profile.
Due to a high level of degradation from DNA samples of Emperor Wu’s limb bones, “decoding his genome presented a more challenging task”, Wen Shaoqing, a professor of archaeology at Fudan University, said, according to a WeChat post from Cell Press, the publisher of the journal.
To address this issue, Wen said they “optimised a new technical solution specifically for highly degraded samples”, including a method to capture short DNA fragments and probes designed specifically for ancient DNA.
Using their new method, the team were able to obtain 1 million usable genetic loci from just 50 milligrams of the emperor’s ground-up bones, “a tenfold improvement over the previous attempt”, Wen said.
The team found that the emperor would have “possessed a typical East or Northeast Asian appearance”, with dark hair, brown eyes and an intermediate to dark skin colour. They also concluded he may have had an increased susceptibility to diseases such as stroke, gout and leukaemia.
Wen said their analysis of the emperor’s bones will allow “historians to discuss in-depth the cause of Emperor Wu’s death in conjunction with historical records”.
Why is China finding it so difficult to close the chapter on Qing history?
Why is China finding it so difficult to close the chapter on Qing history?
The Northern Zhou dynasty ruled over a territory in the heart of China, running from the modern-day northern borders to the far south, and was founded by the nomadic Xianbei people at a time when China was divided between several competing imperial states.
The team’s analysis also concluded that around 60 per cent of his ancestry was Xianbei, the rest of his DNA resembled that of communities found along the Yellow River, suggesting he also had Han Chinese ancestors.
The technique could allow for more detailed research into other ancient skeletal samples, and could allow researchers to solve “more major, high-profile and difficult cases”, Wen said.
In the future, Wen said they plan to analyse more samples from different time periods and ancient cultures, in hopes of “constructing a genetic lineage tree of all East Asian peoples, establishing connections between modern and ancient populations, and writing the ‘genealogy’ of the Chinese nation”.