A story of Crusades told by Crusaders' DNA

History can tell us a lot about the Crusades, the series of religious wars between 1095 and 1291, in which Christian invaders tried to claim the Middle East. But the DNA of nine crusaders from the 13th century buried in a pit in Lebanon shows that there is still much to learn about who the Crusaders were and their interactions with the populations they encountered. The work appears on April 18 in the American Journal of Human Genetics.

The remains suggest that the soldiers composing the Crusader armies were genetically diverse and mixed with the local population of the Near East, although they did not have a lasting effect on the genetics of the living Lebanese. aujourd & # 39; hui. They also highlight the important role that early DNA can play in helping us understand less well-documented historical events.

"We know that Richard the Lionheart went to fight in the Crusades, but we do not know much about the ordinary soldiers who lived there and died, and these ancient examples give us a glimpse of it," says Chris Tyler-Smith, lead author in genetic research at Wellcome Sanger Institute.

"Our results give us an unprecedented view of the ancestry of the people who fought in the Crusaders' army, and it was not just Europeans," says first author Marc Haber, also Wellcome Sanger Institute. "We are witnessing this outstanding genetic diversity in the Middle East during the Middle Ages, with Europeans, Near Eastern peoples and mixed individuals fighting in the Crusades and living and dying side by side."

Archaeological evidence suggests that 25 people whose remains were found in a funeral grave near a Crusader castle near Sidon, Lebanon, were warriors killed in action in the 1200s. On this basis, Tyler- Smith, Haber and their colleagues performed genetic analyzes of the remains and were able to sequence the DNA of nine crusaders, revealing that three Europeans, four Near Easterners and two individuals with different genetic origins.

In the course of history, other massive human migrations, such as the Mongol movement in Asia under Genghis Khan and the arrival of colonial Iberians in South America, have profoundly altered the genetic composition of these regions. But the authors theorize that the influence of the Crusaders was probably short-lived, as the genetic traces of the Crusaders are insignificant among people living in Lebanon today. "They went to great lengths to expel them and were successful after two hundred years," says Tyler-Smith.

This ancient DNA can tell us things about the story that modern DNA can not. In fact, when researchers sequenced the DNA of people living in Lebanon 2,000 years ago in the Roman era, they discovered that the current Lebanese population is actually more genetically similar to that of the Lebanese Roman.

"If you consider the genetics of people who lived in the Roman era and the people who live there today, you would think that there was this continuity.You would think that nothing was safe. "passed between the Roman period and today, and you would miss that for a while, the people of Lebanon included Europeans and people of mixed ancestry," said Haber.

These findings indicate that there may be other major events in human history that do not appear in the DNA of people living today. And if these events are not as well documented as the Crusades, we might just not know them. "Our findings suggest that it is useful to look at ancient DNA even at times when it seemed that little was happening genetically.Our history could be filled with these transient impulses of genetic mixing that disappear without a trace, "says Tyler-Smith.

The fact that the researchers were able to sequence and interpret the DNA of the nine crusaders was also surprising. DNA is degraded more rapidly in hot climates and the remains studied here have been burned and cruelly buried. "The genetics of this area has attracted a lot of interest in the long run because it occupies a strategic position, a long history and many migrations." But previous research focused on current populations, in part because recovery of old DNA in hot climates is very difficult and our success shows that it is now possible to study samples under similar conditions because of advances in DNA extraction and sequencing technologies ", states Haber.

Next, researchers plan to study what was happening genetically in the Middle East during the transition from the Bronze Age to the Iron Age.

But they also hope that this type of study will become more banal and more interdisciplinary. "Historical records are often very fragmented and potentially very biased," said Tyler-Smith. "But genetics gives us a complementary approach that can confirm some of the things we've read in history and tell us things that are not recorded in the historical archives that we have." And as this approach is adopted by historians and archaeologists as a part of their field, I think this will only enrich it more and more. "