Genetic influence of Crusaders short-lived on Lebanese

Massive human migrations, such as the Mongol invasions and conquests of Asia and Eastern Europe by Genghis Khan throughout the 13th century and the Iberian colonization of South America after the 1492 arrival of Christopher Columbus, have left a deep genetic imprint on local populations across the world. But there is little information on the genetic effect left by large waves of Crusaders who went to the Near East to fight between 1095 and 1295 CE, many of whom settled along the Eastern Mediterranean coastline. 

A team, led by geneticists Marc Haber and Chris Tyler-Smith from the Wellcome Sanger Institute, UK, assessed the genetic makeup of the remains of nine soldiers who died in battle near the South Lebanese city of Sidon, an important bastion in the Crusaders’ Kingdom of Jerusalem and a scene of major battles during the 12th and 13th centuries. They also analysed the DNA of four people who lived in the area during the 3rd century, or Roman period, as representative samples of the local ancestry before the Crusades. Their analyses were compared with published genetic data of a large number of ancient and modern individuals, including 99 modern Lebanese.

Obtaining ancient genetic data from hot and humid climates is typically challenging, because these conditions can damage ancient DNA samples. Also, Crusader burial sites are rare. “These new genome sequences are the first genetic data from the Roman and medieval periods from this region,” Haber says. 

Their analyses revealed that all of the soldiers were male. Three were Western Europeans from diverse origins, while four were local Near Easterners. The remaining two were a mixture of European and Near Eastern ancestries, providing direct evidence that the Crusaders admixed with the local population. The team also found from their comparisons of genetic data that, although modern-day Lebanese don’t have genetic signals representing admixture with Europeans, Lebanese Christians are genetically similar with locals from the Roman period. 

“There was a remarkable genetic diversity in the ancient Near East, but this diversity was transient in history, since, with the exception of some Y-chromosomal lineages, the Crusaders’ ancestry has been diluted to undetectable levels in the modern Near Eastern populations,” Tyler-Smith says. The Crusaders’ genetic effect was likely short-lived because the locals made big efforts to expel them, succeeding after a couple of hundred years, he says.

The researchers hope that studies that combine archaeology with genetics will become more commonplace, since historical records on their own can be fragmentary and biased. Genetics can provide a complementary approach that can confirm some of the things in these records and tell us about others that are not recorded, says Tyler-Smith. 

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

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