Y-chromosome and mtDNA polymorphisms in Iraq, a crossroad of the early human dispersal and of post-Neolithic migrations
Introduction
Iraq is an Arabian country bordered by the Arabian gulf, Kuwait, Saudi Arabia (South), Jordan and Syria (West), Turkey (North), and Iran (East) (Fig. 1). Iraq is composed of a mountainous region in the Northeast and a vast desert in the Southwest; in between is the heart of the country, a fertile low land region irrigated by the Tigris and Euphrates rivers, corresponding to the ancient Mesopotamia. The Iraqi population, ca. 21.5 million individuals (July 1995), consists of 75–80% Arabs, 15–20% Kurds, and 5% Assyrians, Turkmen, and others. The official language is Arabic, a Semitic language belonging to the Afro-Asiatic family, but other languages are also spoken: Kurdish (Indo-European), Assyrian (Semitic), and Armenian (Indo-European).
Modern humans are likely to have been present in this area from the time of the exit from Africa around 60,000 years ago, but little information is available about the Palaeolithic period. As for Neolithic times, Iraq represents one of the most important areas for the development and diffusion of agriculture dating from 10,000 years ago onward as testified by many archaeological remains at the Shanidar and Karim Shahir sites (Rashed, 1997). In addition, this region was the source of several ancient civilizations (Sumerians, who first introduced the use of writing, Babylonians, Assyrians, and Caldeans) that profoundly affected other populations of the Middle East, Europe, and elsewhere.
In spite of the importance of this region, genetic studies on the Iraqi population are scarse, aged, and generally restricted to analyses of classical markers (Cavalli-Sforza et al., 1994 and references therein), thus not allowing a dissection of its genetic structure. Analyses of mtDNA and Y-chromosome variation have indicated the central role of the Middle Eastern area in the dispersal of human populations by revealing that it was the probable homeland of numerous mtDNA and Y-chromosome haplogroups (Macaulay et al., 1999; Quintana-Murci et al., 2001; Richards et al., 1998; Semino et al., 2000a; Torroni et al., 1998). However, while extensive studies were carried out in several populations of this region (Comas et al., 1998; Hammer et al., 2000; Nebel et al., 2001; Quintana-Murci et al., 2001; Ritte et al., 1993; Salem et al., 1996; Santachiara-Benerecetti et al., 1993), only few components of mtDNA and Y-chromosome Iraqi gene pool have been evaluated (Quintana-Murci et al., 1999b; Richards et al., 2000). Thus, to increase the knowledge of the genetic structure of that population and to better understand the relationships between the Middle East, Asia Minor, and Europe, we have investigated the extent and nature of mtDNA and Y-chromosome variation in a sample of Iraqi subjects.
Section snippets
Subjects
Blood samples were collected in Baghdad from 216 unrelated adult males (178 Arabs, 25 Assyrians, and 13 Kurds) whose origin was ascertained, at least up to four generations, by oral interview, and who were from different villages and towns along the Tigris and Euphrates rivers. Genomic DNA was extracted from buffy-coats by using standard procedures.
MtDNA analysis
A total of 216 mtDNAs were analyzed for the diagnostic RFLP markers of the most common European, Asian, and African haplogroups (Macaulay et al.,
MtDNA variation
Table 1 shows the haplogroup frequencies obtained by screening all Iraqi mtDNAs for the diagnostic RFLP markers. Their distribution is similar to that of Iran and, in general, to the Middle Eastern populations whereas it substantially differs from that observed in Arabia. Haplogroups HV, H, V, J, T, K, U, I, X, and W encompass about 78% of the Iraqi subjects. This overall frequency is in the range of the other Middle Eastern population values (75.1–80.4%) which are closer to Europe (>90%) than
Discussion
The study of the Iraqi population through the analysis of maternal and paternal markers helps to fill a gap in the picture of the Middle Eastern genetic population structure. As illustrated by the PC analysis of the mtDNA data (Fig. 5), Iraq clusters with the other Middle Eastern populations, and together with Iran, occupies a central position among Arabia, Caucasus, and Europe. The first component separates Arabia from the others, mainly from Europe and Caucasus, being the Arabia characterized
Acknowledgements
This research was supported by the Italian Ministry of the University, Progetti Ricerca Interesse Nazionale 1999 and 2002 (to A.S.S.-B. and A.T.), Progetto Finalizzato C.N.R. “Beni Culturali” (to A.S.S.-B.), as well as from Fondo d’Ateneo per la Ricerca dell’Università di Pavia (to A.S.S.-B. and A.T.). N.A.-Z. was supported by ICGBE (Trieste) and University of Pavia fellowships.
References (78)
- et al.
High-resolution analysis of human Y chromosome variation shows a sharp discontinuity and limited gene flow between Northwestern Africa and Iberian Peninsula
Am. Hum. Genet.
(2001) - et al.
Mutation rate in human microsatellites: influence of the structure and length of the tandem repeat
Am. J. Hum. Genet.
(1998) - et al.
Trading genes along the silk road: mtDNA sequences and the origin of central Asian populations
Am. J. Hum. Genet.
(1998) - et al.
A back migration from Asia to sub-Saharan Africa is supported by high-resolution analysis of human Y-chromosome haplotypes
Am. J. Hum. Genet.
(2002) - et al.
Phylogenetic network for European mtDNA
Am. J. Hum. Genet.
(2001) - et al.
A short tandem repeat-based phylogeny for the human Y chromosome
Am. J. Hum. Genet.
(2000) - et al.
Paternal population history of East Asia: sources, patterns, and microevolutionary processes
Am. J. Hum. Genet.
(2001) - et al.
The emerging tree of West Eurasian mtDNAs: a synthesis of control-region sequences and RFLPs
Am. J. Hum. Genet.
(1999) - et al.
Human evolution and the Y chromosome
Curr. Opin. Genet. Dev.
(1996) - et al.
The Y chromosome pool of Jews as part of the genetic landscape of the Middle East
Am. J. Hum. Genet.
(2001)
The 49a,f haplotype 11 is a new marker of the EU19 lineage that traces migrations from northern regions of the Black Sea
Hum. Immunol.
Different genetic components in the Ethiopian population, identified by mtDNA and Y-Chromosome polymorphisms
Am. J. Hum. Genet.
Human genetic affinities for Y-chromosome P49a.,f/TaqI haplotypes show strong correspondence with linguistics
Am. J. Hum. Genet.
Y-chromosome lineages trace diffusion of people and languages in southwestern Asia
Am. J. Hum. Genet.
Tracing European founder lineages in the Near Eastern mtDNA pool
Am. J. Hum. Genet.
In search of geographical patterns in European mitochondrial DNA
Am. J. Hum. Genet.
Human Y-chromosome variation in the western Mediterranean area: implications for the peopling of the region
Hum. Immunol.
Combined use of biallelic and microsatellite Y-chromosome polymorphisms to infer affinities among African populations
Am. J. Hum. Genet.
Ethiopians and Khoisan share the deepest clades of the human Y-chromosome phylogeny
Am. J. Hum. Genet.
mtDNA analysis reveals a major late Paleolithic population expansion from southwestern to northeastern Europe
Am. J. Hum. Genet.
The A1555G mutation in the 12S rRNA gene of human mtDNA: recurrent origins and founder events in families affected by sensorineural deafness
Am. J. Hum. Genet.
Melting curve analysis of SNPs (McSNP): a gel-free and inexpensive approach for SNP
Genotyping Biotech.
Sequence and organization of the human mitochondrial genome
Nature
Reanalysis and revision of the Cambridge reference sequence for human mitochondrial DNA
Nat. Genet.
Mitochondrial portraits of human populations using median networks
Genetics
A human Y-linked DNA polymorphism and its potential for estimating genetic and evolutionary distance
Science
The History and Geography of Human Genes
Branching pattern in the evolutionary tree for human mitochondrial DNA
Proc. Natl. Acad. Sci. USA
Genetics and history of sub-Saharan Africa
Year Book Phys. Anthropol.
The molecular diversity of the Niokholo Mandenkalu from Eastern Senegal: an insight into West Africa genetic history
Y chromosomal DNA variation and the peopling of Japan
Am. J. Hum. Genet.
A recent insertion of an Alu element on the Y chromosome is a useful marker for human population studies
Mol. Biol. Evol.
Out of Africa and back again: nested cladistic analysis of human Y chromosome variation
Mol. Biol. Evol.
Jewish and Middle Eastern non-Jewish populations share a common pool of Y-chromosome biallelic haplotypes
Proc. Natl. Acad. Sci. USA
The geographic distribution of human Y chromosome variation
Genetics
Mitochondrial DNA and Y chromosome-specific polymorphisms in the Seminole Tribe of Florida
Eur. J. Hum. Genet.
Mitochondrial genome variation and the origin of modern humans
Nature
The place of the Indian mitochondrial DNA variations in the global network of maternal lineages and the peopling of the old world
Cited by (116)
The Y-chromosome of the Soliga, an ancient forest-dwelling tribe of South India
2020, Gene: XCitation Excerpt :In turn, J2 emerged somewhere within western Asia (Caucasus Mountains, Mesopotamia and the Levant) around 15 to 22 Kya (Zalloua and Wells, 2004; Al-Zahery et al., 2003, 2011), or 19 to 24 Kya (Batini et al., 2015). Associated with the spread of agriculture from the Fertile Crescent to points west (Europe), east (South Asia) and south (Africa) during the Neolithic Era (Zalloua and Wells, 2004; Al-Zahery et al., 2003, 2011), J2 is found in substantial concentrations in Europe, western Asia, South Asia and northern Africa. This distribution is consistent with the J2 contour map (Fig. 5) and J2 network (Fig. 10), which includes only populations from West Asia, South Asia and the neighboring Himalayan collections.
Phylogeographic history of mitochondrial haplogroup J in Scandinavia
2023, American Journal of Biological Anthropology