Y-chromosome DNA haplotypes in North African populations

Human Biology, Jun 2000 by Lucotte, Gerard, Aouizerate, Annie, Berriche, Sala

Abstract The frequency distribution of Y-chromosome haplotypes at DNA polymorphism p49/TaqI was studied in a sample of 505 North Africans from Mauritania, Morocco, Algeria, Tunisia, Libya, and Egypt. A particulary high frequency (55.0%) of Y-haplotype 5 (A2,CO,DO,F1,11 ) was observed in these populations, with a relative predominance in those of Berber origin. Examination of the relative frequencies of other haplotypes in these populations, mainly haplotype 4 (the "African" haplotype), haplotype 15 (the "European" haplotype), and haplotypes 7 and 8 (the "Near-East" haplotypes), permit useful comparisons with neighboring peoples living in sub-Saharan Africa, Europe, and the Near East.

KEY WORDS: Y-CHROMOSOME HAPLOTYPES, GEOGRAPHIC DISTRIBUTION, NORTH AFRICA, MEDITERRANEAN

Because they relate to paternal ancestry, variations in DNA sequences that are specific to the nonrecombinant part of the human Y chromosome are particularly interesting from an evolutionary point of view. The probes 49f and 49a (locus DYSI ), located at Yq.11.2 (Quack et al. 1988), are able to identify 18 genomic TaqI fragments (named alphabetically, A-R), most of them being male specific. Among these the A, B, C, D, E, and I fragments can be either present or absent in males, or show variations in size (Lucotte and Ngo 1985). In the first group studied (Ngo et al. 1986), which included 50 Caucasians, 15 Africans, and 10 Asians living in Paris, 16 combinations of these DNA polymorphisms, or haplotypes (numbered 1-16), were detected. The present study examines haplotype frequencies in populations of North Africa.

In pre-Neolithic times (about 7000-3000 BP) the Mediterranean and Red Sea coasts of North Africa were populated by white, Hamite-speaking peoples, who have come to be called Berbers and Egyptians. In Pharaonic Africa (3000 years BP) the population had suffered drastic changes, with agricultural Egypt having 1 million people. Climatic changes had dried northern Africa by around 8000-4000 years BP; the forest line had retreated towards the Equator from about the 16th parallel by 3000 years BP, and the Sahara had assumed the characteristics it has today. Heavy migrations towards the North sent people to the Mediterranean coast, the Iberian peninsula, and the Canary islands.

The population of North Africa has followed the general Maghreb demographic movements. In Neolithic times, a scattering of Berber pastoralists and cultivators existed there; however, they remained at a Neolithic level of civilization, while other Mediterranean peoples were evolving through the Bronze and Iron Ages. Around 1000 years BP, the Phoenicians came upon a stone-age Neolithic culture in the Maghreb; they established Carthage (in Tunisia) only to be overthrown by the Romans in 146 BP. At this time there were 100,000 Phoenicians and 500,000 Berbers in Tunisia, plus another 2.5 million Berbers in the rest of North Africa. During the 7th century CE, Arabs invaded North Africa, imposing their religion and language on the Berbers, a process that culminated with the Bedouin reaching the Maghreb in the 11th century. Later arrivals to North Africa in colonial times included the Portuguese and Spanish in Morocco; the French in Morocco, Algeria, and Tunisia; the Italians in Libya; and the Turks in Egypt.

A main problem of Mediterranean ethnography has been the lack of DNA markers from southern Mediterranean populations (Arnaiz-Villena et al. 1995). Bosch et al. (1997) have recently synthetized evidence from classical genetic markers in North Africa. In the present study, p49 TaqI Y-- haplotypes were studied in a sample of 7 North African populations, and haplotypic comparisons were made with other African, European, and Asiatic populations previously studied for these haplotypes. (Persichetti et al. [1992] studied a small sample of 34 unrelated Egyptian males for this haplotype.) The approach in the haplotype diversity measures adopted here extends our previous work on Y-haplotype distributions in Europe (Lucotte and Hazout 1996), using Shannon entropy (H) as a measure of heterozygosity, numbers of haplotype equivalents as expected H, and genetic distances as the difference between 2 entropies: the first being calculated after grouping the haplotype distributions of two compared samples, and the second corresponding to the weighted sums of the entropies calculated for each sample.

Subjects and Methods

Samples and Populations. All 505 samples studied (Figure 1) correspond to unrelated adult North African males, whose origin is based on the birthplace of their fathers and (at least) grandfathers. The Mauritanian sample is composed of 25 males, collected previously for anthropological studies concerning African populations (Lucotte et al. 1994). The Berber sample consisted of 74 Berbers native to Morocco and living near Marrakech. The main part of the North African sample is composed of 102 unrelated males (excluding those of Berber origins) born in Morocco, of 141 males from Algeria, and of 73 males from Tunisia, all living in Paris. Also included are 38 Libyan and 52 Egyptian males (originating from the northern part of Egypt), from whom blood samples were collected in their countries of origin.