PMC:2427286 / 1543-4110 JSONTXT

{"project":"2_test","denotations":[{"id":"18374297-12897772-2052336","span":{"begin":2260,"end":2261},"obj":"12897772"}],"text":"Introduction\nCompared with other ape species, humans show little genetic variation, despite their much larger population size and wider distribution, and this limited variation can mostly be explained by geographical factors.1 Human populations, however, can be classified in many other ways, such as by language, ethnicity, or religion. Populations in which these alternative factors have had a greater influence than geography on the distribution of genetic variation are unusual and merit particular attention. Here, we describe the genetic structure of the peoples of Lebanon, show that religion has had a strong influence on current patterns of patrilineal variation, and identify historical events that might underlie this unusual situation.\nLebanon is a small country on the eastern coast of the Mediterranean (Figure 1). Just 4,015 square miles in area, it is 1/60th the size of Texas and half the size of Wales. This region was first occupied by fully modern humans ∼47,000 years ago1 and appears to have remained habitable even during the unfavorable conditions of the last glacial maximum 18,000–21,000 years ago.2 It is close to the Fertile Crescent where the West Asian Neolithic transition began ∼10,000 years ago1, was conquered by the Assyrians, Babylonians, Persians, and Romans, and was visited by the Egyptians and Greeks.3, 4, 5, 6 Among well-documented events within more recent historical times, three could potentially have involved significant immigration into the country. First, the Muslim expansion beginning in the 7th century CE introduced the Islamic faith from its origin in the Arabian Peninsula.7 Second, in the 11th–13th centuries CE, the Crusades resulted in the establishment of enclaves by substantial numbers of European Christians. 3, 4, 5, 7, 8 Finally, in the 16th century CE, the Ottoman Empire expanded into this region and remained until the early part of the 20th century.3 The current Lebanese population of almost four million people thus consists of a wide variety of ethnicities and religions, including Muslim, Christian, Druze, and others.\nThe Y chromosome carries the largest nonrecombining segment in the human genome, and consequently its haplotypes provide a rich source of information about male history.9 We set out to establish the extent of Y-chromosomal variation in Lebanon to determine whether this varies between subpopulations identified on the basis of geographical origin or religious affiliation and, if it does, to what extent such variation could be related to known historic or prehistoric events."}