The team says it found a particular DNA signature which recently appeared in Lebanon and is probably linked to the crusades. The finding comes from the Genographic Project, a major effort to track human migrations through DNA.

The researchers detected that some Christian men in Lebanon carry a DNA signature hailing from Western Europe. The scientists also found that Lebanese Muslim men were more likely than Christians to carry a particular genetic signature. But this one is linked to expansions from the Arabian Peninsula which brought Islam to the area in the 7th and 8th Centuries. But they emphasize that the differences between the two communities are minor, and that Christians and Muslim Arabs in Lebanon overwhelmingly share a common heritage.

The study focused on the Y, or male, chromosome, a package of genetic material carried only by men that is passed down from father to son more or less unchanged, just like a surname. But over many generations, the chromosome accumulates small changes, or copying errors, in its DNA sequence. These can be used to classify male chromosomes into different groups which, to some extent, reflect a person's geographical ancestry.

The team analyzed the Y chromosomes of 926 Lebanese males and found that patterns of male genetic variation in Lebanon fell more along religious lines than along geographical lines. A genetic signature on the male chromosome called WES1, which is usually only found in west European populations, was found among the Lebanese men included in the study.

References:

https://www3.nationalgeographic.com/genographic/lebanon.html

http://en.wikipedia.org/wiki/The_Genographic_Project