Autosomal genetics and Y-chromosome haplogroup L1b-M317 reveal Mount Lebanon Maronites as a persistently non-emigrating population

Abstract

Currently, there are 18 different religious communities living in Lebanon. While evolving primarily within Lebanon, these communities show a level of local isolation as demonstrated previously from their Y-haplogroup distributions. In order to trace the origins and migratory patterns that may have led to the genetic isolation and autosomal clustering in some of these communities we analyzed Y-chromosome STR and SNP sample data from 6327 individuals, in addition to whole genome autosomal sample data from 609 individuals, from Mount Lebanon and other surrounding communities. We observed Y chromosome L1b Levantine STR branching that occurred around 5000 years ago. Autosomal DNA analyses suggest that the North Lebanese Mountain Maronite community possesses an ancestral Fertile Crescent genetic component distinct from other populations in the region. We suggest that the Levantine L1b group split from the Caucasus ancestral group around 7300 years ago and migrated to the Levant. This event was distinct from the earlier expansions from the Caucasus region that contributed to the wider Levantine populations. Differential cultural adaption by populations from the North Lebanese Mountains are clearly aligned with the L1b haplotype STR haplogroup clusters, indicating pre-existing and persistent cultural barriers marked by the transmission of L1b lineages. Our findings highlight the value of uniparental haplogroups and STR haplotype data for elucidating biosocial events among these populations.

Fig. 1. Reduced median network of L1b M20 showing 13 STR haplotype distribution among populations; area is proportional to haplotype frequency, and color indicates populations.

Connecting lines represent putative phylogenetic relationships between haplotypes. The three heavily localized branches that share a common root from the L1b network are assigned on the figure as UEP2, UEP3, and UEP4. Color code: Arabia - purple, Caucasus - brown, Egypt - yellow, Greece - blue, Italy - pink, Levant - dark green, Libya - light blue, NLMM - light green, Mesopotamia - orange, and Turkey - red.

Fig. 2. PCA computed and displayed for the full list of populations indicated in Supplementary Tables 2 and 6.

a PCA components 1 and 2 for recent and ancient regional populations, highlighting differentiation of NLMM from all other regional populations. b Mutual information scaling for principal components indicating shared bitwise genotypic information between samples and principal components.

Fig. 3. ADMIXTURE plot for admixtures computed on the full population list with populations plotted listed in Supplementary Tables 2 and 6.

ADMIXTURE ancestral components computed for regional populations with K = 4 and 5 shows that NLMM contains the strongest regional representation of an ancestral component found distributed among Levantine and Fertile Crescent populations.

Fig. 4. Patterns of homozygosity in 4 religious groups in Lebanon.

Plots of homozygosity computed a by co-ancestry, and b runs of homozygosity between strands per sample, showing a frequency chart as a fiddle diagram, and median and 95% quantiles of the fixation coefficients.