Ana M González; José M Larruga; Khaled K Abu-Amero; Yufei Shi; José Pestano; Vicente M Cabrera

“ However, selection pressure is higher in the coding than in the regulatory region so that the substitution rate is ten times faster in the latter. The mean coding/regulatory ratio is 8.3 for M1a2 lineages and only 2.4 for the rest of M1. We interpret these results as due to different ages of expansion between clades. M1a2 would be the youngest clade with a more recent expansion than the others so that purifying selection has not had enough time to eliminate mutations with small deleterious effects in the coding region. ”

“ The earliest M1 expansion into Africa occurred in northwestern instead of northeastern areas; this early spread reached the Iberian Peninsula even affecting the Basques. The majority of the M1a lineages found outside and inside Africa had a more recent eastern Africa origin. Both western and eastern M1 lineages participated in the Neolithic colonization of the Sahara. The striking parallelism between subclade ages and geographic distribution of M1 and its North African U6 counterpart strongly reinforces this scenario. ”

“ Radiation ages and evolution of lineages
Radiation ages for M1 and its subhaplogroups have been estimated on the basis of complete coding and HVSI sequences using different mutation rate estimations (Table 4) . The ages obtained for M1 and M1a from HVSI data are more coherent with those calculated for the coding region using the Ingman et al. [6] mutation rate than that proposed by Mishmar et al. [ [38] . Our coalescence age estimations for the whole M1 clade (20,000–30,000 years) are younger than those previously published [ [21] ”

“ Outside Africa and the Iberian Peninsula, as with U6, M1 has been mainly detected in other Mediterranean areas with main incidences in islands such as Sicily. It is customary to attribute these incidences to the above mentioned Arab/Berber historic occupations. However, taking into account the major Jewish assignation for all the M1a haplotypes detected in Europe, the possibility of a Jewish maternal ascendance for at least some of these lineages should not be rejected. ”

“ Within this sparse but geographically wide range of M1 distribution its three identified branches also had uneven radiations. Although M1a (HVSI identified by the 16359 transition) is present in all the M1 range, its greatest frequencies and diversities are found in Ethiopia and eastern Africa (Table 2) , pointing to this area as the most probable origin of the M1a expansion in all directions, with particular incidence in western Asia and sub-Saharan Africa. Not all the M1b lineages can be HVSI identified ”

“ It must be stated that coalescence ages are only rough estimations biased by mutation rate estimations, small sample size, demographic history and, possibly, selection. There are recent examples of clock-like evolution violations in several mtDNA lineages that have been explained by selective or demographic effects [ [39] - [40] . Here, subclade M1a2 (Fig. 1) represents a new example of constant mutation rate violation. The mean number of substitutions accumulated in M1a2 lineages (12.5 ± 0.7) is significantly higher (p = 0.008) than that in the rest of M1 lineages (8.4 ± 1.3) . ”

“ Consistently, none of our M1b sequences from western areas has that motif. The last cluster, M1a, was first distinguished by RFLP +12345 RsaI [21] and, after that, further characterized by transition 16359 [ [19] . In addition it also has transition 3705 at its root (Fig. 1) . M1a is the most prominent clade in eastern Africa. However, its expansion occurred later than the other M1 branches (Fig. 1) . An M1a subclade, M1a2, defined by transition 9053, that can be RFLP diagnosed (Table 1) , testifies a posterior spread of M1a to western Asia. ”

“ A posterior East to West African expansion around 17,000 ya was indicated by the U6a1 relative diversity and distribution. Again, age, relative East to West diversities and geographic range accurately correspond with the M1a1 expansion detected here. More recent local spread of lineages U6b and U6c also parallel the M1b and M1c1 distributions. Furthermore, these similarities also hold outside Africa. U6 lineages in the Iberian Peninsula have been considered traces of northward expansions from Africa. ”

“ There are striking similarities between the geographical dispersals and radiation ages observed here for M1 lineages and those previously published for the North African U6 haplogroup [41] . It was proposed that U6a first spread was in Northwest Africa around 30,000 ya. Coalescence ages for M1 also fit into this period and the oldest clade M1c has an evident northwestern Africa distribution ”

“ However, it is rare in continental Europe. Although in low frequencies, its presence in the Middle East has been well established from the South of the Arabian Peninsula to Anatolia and from the Levant to Iran. ”

“ The low sea level in the Gibraltar Strait at that time could also facilitate the Iberian Peninsula colonization. The northwestern African M1c and the probable north central M1b expansions are coincidental with the Iberomaurusian and Capsian industries. The anomalous evolution of M1a2 lineages left the coalescence ages of the eastern Africa M1a expansion uncertain, but as suggested for the sister U6a1 radiation ”

“ Oefner, PJ & Cavalli-Sforza, LL (2001) , The phylogeography of Y chromosome binary haplotypes and the origins of modern human populations, vol. 65, pp. 43–62, 1141552210.1046/j.1469-1809.2001.6510043.x, pmid:11415522, DOI 10.1046/j.1469-1809.2001.6510043.x ↑ Watson, E; Forster, P; Richards, M & Bandelt, HJ (1997) , Mitochondrial footprints of human expansions in Africa, vol. 61, pp. 691–704, 9326335, pmid:9326335 1 2 3 4 5 6 7 Maca-Meyer, N; González, AM; Larruga, JM; Flores, C & Cabrera, VM (2001) , Major genomic mitochondrial lineages delineate early human expansions, vol. ”