Advances in DNA technology increasingly enable the writing and rewriting of the past, Fang Aiqing and Xu Xiaomin report.

Wen Shaoqing's work is about breaking boundaries and exploring where his imagination leads him. Journalists have been chasing the molecular biologist-turned-archaeologist since September when his team at Fudan University's Institute for Archaeological Science uncovered the touching stories hidden in the remains of unidentified martyrs of the War of Resistance Against Japanese Aggression (1931-45) and the subsequent War of Liberation (1946-49).

The team's efforts involving forensic DNA techniques continue to this day in the hope that relatives of these obscure heroes will finally be able to find long-lost family members.

Wen, who is an associate professor at the institute, has also been involved in research such as analyzing the dietary habits of an ancient emperor and his queen and the causes of their deaths, as well as the interaction and integration of ancient ethnic groups in what is now northern China.

As his team's more interesting findings become known to the public, especially those involving the analysis of ancient DNA, the potential of archaeological science to solve long-standing historical mysteries becomes more widely recognized in China.

Emotional stories

In June 1942, a crucial battle against the Japanese invaders took place in Xuecun village in Suning county, Hebei province. More than 1,000 Chinese soldiers and officers sacrificed their lives, including two top officers, Chang Deshan and Wang Yuanyin.

Villagers buried them in mass graves and have visited to pay their respects every April on Tomb Sweeping Day, ever since.

This April, Wen and his colleagues and students helped local officials move some of the remains for better preservation, collecting physical data in the process.

In June, they released the results of their preliminary analysis based on physical anthropology.

The remains belonged to at least 101 individuals. Four showed traces of comminuted fractures (where a bone is broken into multiple fragments), two of injury by sharp objects, and another had bullet wounds.

Wen speculates that the impact of weapons like machine guns caused the comminuted fractures, indicating the cruelty of war.

He says that it's worth noting that the young males — very likely soldiers — were buried with people of both genders of all ages.

The team was able to identify the gender of 52 individuals, 42 of whom were male or presumed male. Among the 79 that could be identified by age, 15 were underage — the youngest was a 1-year-old — 45 were aged between 15 and 35, 15 were between 36 and 55, and four were elderly.

As to who the elderly, women and children were, Wen says that further isotopic analysis and DNA identification work they are carrying out might be able to confirm whether they were noncombat army personnel, or villagers that the soldiers failed in trying to help escape the battle.

Wen explains that strontium isotopes will identify whether the bodies belong to local residents or outsiders, while carbon and nitrogen isotopes reveal information about lifestyle and nutritional status. Facial reconstruction based on cranial computed tomography will also be performed on 35 well-preserved skulls.

For the past nine years, the team has built a DNA database of around 1,200 national heroes who sacrificed their lives for the country and its people.

This effort paid off when they managed to help Shanxi retiree Cui Yuqi fulfill his late father's wish of finding his brother who died during the War of Liberation in 1947 at the age of 23 in Lyuliang, Shanxi province.

Based on records and interviews with villagers, local officials speculated that the brother, who was called Cui Haizhi, was likely buried in a martyrs' cemetery in Nancun village in Fangshan county because the cemetery was located near a wartime hospital and was used to bury those who could not be saved.

In January of last year, accompanied by four young scholars and 11 students, Wen excavated the cemetery and unearthed 49 bodies, as well as belongings such as buttons, enamel bowls, iron spoons, pipes, jade seals and bullets. The remains were properly reburied later.

The team extracted the skeletons and cleaned them on-site, collecting physical anthropological information before conducting lab tests to establish a DNA archive, confirming the gender and age of the martyrs, traumas and illnesses suffered during their lifetimes, and clues about their personal lives. The results were made public at an exhibition at Fudan last September.

Wen says that the work was very emotional.

The martyrs' average age was 20.5, with the youngest not even 14. Many showed traces of wounds or of suffering from degenerative joint diseases at a very young age. Five had undergone amputations, with the cut marks and evidence of infection indicating that the amputations were performed under rudimentary conditions.

Some of the bones had bullet holes, sometimes more than one, inferring that as the soldiers advanced against the enemy, bullets came mostly from the front.

Taking part in his first field study, Wang Ke, a graduate student at Fudan's Department of Cultural Heritage and Museology, was shocked to discover as he swept the dirt from one of the bodies that its epiphyseal plates (plates of cartilage at the end of growing bones) had not yet fully closed, indicating that they belonged to an adolescent.

"At that age, I was in high school, still childish and sometimes fooling around. But my peers decades ago were fighting on battlefields and risking their lives," Wang says.

In Lyuliang, Wen's team re-created facial appearances for the first time. After scanning the skulls, they added anatomical markers when they returned to the lab.

Based on the cranial CT scan data of thousands of contemporary people of both genders and of different ages they had previously collected and information on the average thickness of muscular and soft tissues, combined with the physical information of the remains, they were able to make 43 successful digital facial re-creations.

"Studying these undocumented soldiers buried in Nancun helps us learn about revolutionary history from a grassroots perspective, how they lived and what they went through.

"They cannot and should not be forgotten. We hope their loved ones are able to find them and they will eventually have names and photos on their gravestones," Wen says.

Through DNA matching, Cui Yuqi was able to find his uncle Cui Haizhi, whose high nose bridge, thin lips and narrow eyes resembled those of his father.

Small finds, big progress

The 42-year-old molecular archaeologist used to study bioscience. In 2014, when he was a doctoral candidate at Fudan's School of Life Sciences, he joined a program overseen by historian Han Sheng and molecular anthropologist Li Hui to trace the pedigree of Cao Cao, an iconic warlord in late Eastern Han Dynasty (25-220).

As part of the program, researchers collected and analyzed genetic samples of contemporary males with the Cao surname from across the country — particularly those who claim to be descendants of Cao Cao — and later compared their Y-DNA with that of the warlord's granduncle Cao Ding, whose remains include two teeth, from which the researchers were able to extract a DNA sample.

For Wen, the program was a door into the world of ancient DNA, which over the past decade has shown great potential in the study of the origins and migration of human populations, changes to social structure, cultural exchange and the spread of diseases.

In 2022, Swedish geneticist Svante Paabo received the Nobel Prize in physiology or medicine for his discoveries concerning the genomes of extinct hominids and human evolution, a milestone in the research of ancient DNA.

Wen likes the fact that addressing questions of history through the study of ancient DNA is straightforward and compelling.

His research includes tracing the spread and hidden connections between the Neolithic Yangshao and Longshan cultures in the middle and lower reaches of the Yellow River, as well as changes to social structure in the pre-Qin period (before 221 BC), by looking into migration and genetic lineage.

In addition, a major strand of his work involves uncovering evidence of the interaction and integration of different ethnic groups with a presence in today's northern China, including the Xiongnu, Turks, Xianbei, Tuyuhun nomads and the Sogdians, who were active on the Silk Road, through the third to the ninth centuries.

The project was launched in 2021 and research teams specializing in multiple disciplines such as history, archaeology, genetics, ethnology and linguistics are involved.

One notable achievement has been the team's research into Yuwen Yong, Emperor Wudi of the Northern Zhou Dynasty (557-581), and his wife Queen Ashina.

The emperor was a member of the Xianbei ethnic group and succeeded to the throne at 17. He unified northern China and died at the age of 36 on an expedition to the Turkic tribes to the north, led by his father-in-law.

Genomic analysis suggests that 30 percent of Wudi's ancestry derived from agricultural populations in the Yellow River Basin, which, according to Wen, likely resulted from long-term intermarriage between the Xianbei royal family and Han nobility.

Meanwhile, laboratory tests and historical data indicate that the emperor died of chronic arsenic poisoning, the result of taking Taoist elixirs in pursuit of longevity, while Queen Ashina's bones contain a high level of lead from the cosmetics she used.

Wen says that the project is also exploring the ethnic structure of the Tang Dynasty (618-907) capital Chang'an — today's Xi'an in Shaanxi province — which had a population of over a million at its peak and attracted merchants from across China and beyond.

He says that the relatively cold and dry climate of northern China aids the survival of biological remains like teeth and bones, whereas in southern China, where it is more humid and the soil is more acidic, remains are less well-preserved and so they often analyze the DNA of sedimentary deposits to learn about the ancient environment or to determine what vessels contained and where they came from.

While Wen is focused more on the study of human bones, some of his colleagues and students in the team of 30 focus on animal bones and plants — for example, the domestication and evolution of horses and the spread of grapes in ancient China.

Having studied at Durham University and the University of Oxford in the United Kingdom, Zhou Yu, a doctoral candidate and team member, has an interest in long-distance trade and the historical spread of crops.

Realizing that grapes and grape products played a crucial role in historical trade, cultural and religious exchanges in many parts of Eurasia, she decided to make grapes her focus of research.

"Ancient plant DNA is important to the study of the origins of agriculture and the propagation and evolution of crops," Zhou says, adding that research on existing grape genomes provides the necessary basis for her study.

However, as the challenge lies in extracting ancient plant DNA from poorly preserved remains, she is trying to collect grape seeds that have not carbonized and is exploring more efficient methods that can potentially be applied to the research of plant remains.

Wen says that after they were given the limb bone samples of Emperor Wudi and Queen Ashina in 2015, they spent almost eight years optimizing research methods to extract previously unobtainable DNA data.

He is looking forward to the embrace of DNA by multiple disciplines, especially history and archaeology, to deepen the interpretations of their findings.

"As we solve long-standing mysteries, other deeper questions emerge and wait to be examined through joint efforts," he says.

Contact the writers at fangaiqing@chinadaily.com.cn