Generally, the DNA in a man’s Y-chromosome contains information about prehistoric migrations that happened many millennia in the past. But a recent study of men in Lebanon shows that genetics can be a reflection of more recent events as well.
A paper published in the April issue of the American Journal of Human Genetics shows that two major events in the history of religion — the spread of Islam and the Crusades — have left their mark on Lebanon’s male population.
The authors of the AJHG paper showed that a disproportionate percentage of Muslim men in Lebanon have Y-chromosomes of a type that is common on the Arabian peninsula. Migrants from Arabia brought Islam to Lebanon during the 7th century.
Similarly, a disproportionate number of Lebanese Christian and Druze men have Y-chromosomes similar to those found in western Europe. In fact, the most common Y-chromosome signature in Lebanon is most abundant in France, Spain, northern Italy and the Low Countries. But it is found nowhere else east of Hungary.
The authors of the AJHG paper attribute that remarkable genetic connection to the Crusades, a series of military campaigns by European invaders against Jerusalem and other cities of religious significance in the Near East.
There is also an indication that men from Turkey introduced their genes into the Lebanese population during the time of the Ottoman Empire, which ruled Lebanon from the 16th to 20th centuries.
In most countries, geography is the most significant factor influencing the genetic variability of the population. But in Lebanon, religion accounts for more than three times as much genetic variation as geography.
“Such structure might arise only when several unusual criteria are met,” the AJHG paper concludes. “Migrations based on religion must take place between areas with different representative Y-chromosomal types, and they must establish genetically differentiated communities that remain stable over long time periods. In Lebanon, these conditions appear to have been met for over 1,300 years.”