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The history of human inbreeding is controversial.(1) In particular, how the development of sedentary and/or agricultural societies may have influenced overall inbreeding levels, relative to those of hunter-gatherer communities, is unclear.(2-5) Here, we present an approach for reliable estimation of runs of homozygosity (ROHs) in genomes with >= 3x mean sequence coverage across >1 million SNPs and apply this to 411 ancient Eurasian genomes from the last 15,000 years.(5-34) We show that the frequency of inbreeding, as measured by ROHs, has decreased over time. The strongest effect is associated with the Neolithic transition, but the trend has since continued, indicating a population size effect on inbreeding prevalence. We further show that most inbreeding in our historical sample can be attributed to small population size instead of consanguinity. Cases of high consanguinity were rare and only observed among members of farming societies in our sample. Despite the lack of evidence for common consanguinity in our ancient sample, consanguineous traditions are today prevalent in various modem-day Eurasian societies,(1, 35-37) suggesting that such practices may have become widespread within the last few millennia.

Birand, Aysegul/0000-0001-9217-3627; Parvizi, Poorya/0000-0002-1282-765X WOS: 000430461100014 PubMed: 29399779 ObjectivesNorth Mesopotamia has witnessed dramatic social change during the Holocene, but the impact of these events on its demographic history is poorly understood. Here, we study this question by analysing genetic data from the recently excavated Late Iron Age settlement of Cemialo Srt in Batman, southeast Turkey. Archaeological and radiocarbon evidence indicate that the site was inhabited during the second and first millennia BCE. Cemialo Srt reveals nomadic items of the Early Iron Age, as well as items associated with the Late Achaemenid and subsequent Hellenistic Periods. We compare Cemialo Srt mitochondrial DNA profiles with earlier and later populations from west Eurasia to describe genetic continuity patterns in the region. Materials and methodsA total of 16 Cemialo Srt individuals' remains were studied. PCR and Sanger sequencing were used to obtain mitochondrial DNA HVRI-HVRII sequences. We studied haplotype diversity and pairwise genetic distances using F-ST, comparing the Cemialo Srt population with ancient and modern-day populations from west Eurasia. Coalescent simulations were carried out to test continuity for specific population comparisons. ResultsMitochondrial DNA (mtDNA) haplotypes from 12 Cemialo Srt individuals reveal high haplotype diversity in this population, conspicuously higher than early Holocene west Eurasian populations, which supports the notion of increasing population admixture in west Eurasia through the Holocene. In its mtDNA composition, Cemialo Srt shows highest affinity to Neolithic north Syria and Neolithic Anatolia among ancient populations studied, and to modern-day southwest Asian populations. Based on population genetic simulations we cannot reject continuity between Neolithic and Iron Age, or between Iron Age and present-day populations of the region. DiscussionDespite the region's complex sociopolitical history and indication for increased genetic diversity over time, we find no evidence for sharp shifts in north Mesopotamian maternal genetic composition within the last 10,000 years. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114Z159]; METUMiddle East Technical University [BAP-07-02-2015-003] Scientific and Technological Research Council of Turkey (TUBITAK), Grant/Award Number: 114Z159; METU, Grant/Award Number: BAP-07-02-2015-003