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Tema: Origen genético de la población canaria

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    Origen genético de la población canaria

    Este interesante estudio viene a arrojar las siguientes conclusiones:

    a.) Conforme al ANALISIS del Cromosoma Y: Más del 90% de la población originaria de canarias (abuelo paterno canario), desciende de aportes genéticos europeos (península ibérica fundamentalmente). El resto procede fundamentalmente de aborígenes canarios (amazigh) (6-8%), existiendo además algunas trazas (<1%) de influencia negroide (esclavos traidos tras la conquista para los ingenios azucareros).

    b.) Conforme a los estudios del ADN Mitocondrial: la influencia aborigen por vía materna rondaría el 45%.

    Las diferencias entre los aportes por "via paterna frente a la materna", nos hablan también de la desproporción entre hombres y mujeres de los primeros días de la conquista entre los contingentes ibéricos, y la unión por tanto entre hombres de procedencia europea y mujeres aborígenes.

    Hay divergencias entre islas, siendo Gomera y Fuerteventura, las islas con un mayor aporte genético Amazigh.

    A Predominant European Ancestry of Paternal Lineages from Canary Islanders

    C. Flores1,2, N. Maca-Meyer1, J. A. P´ erez1, A. M. Gonz´ alez1, J. M. Larruga1 and V. M. Cabrera1,

    1
    Departamento de Gen´etica, Universidad de La Laguna, Canary Islands

    2



    Unidad de Investigaci´on, Hospital Universitario N.S. de Candelaria, Canary Islands



    Summary

    We genotyped 24 biallelic sites and 5 microsatellites from the non-recombining portion of the Y chromosome in 652 males from the Canary Islands. The results indicate that, contrary to mtDNA data, paternal lineages of the current population are overwhelmingly (>90%) of European origin, arguing for a highly asymmetric pattern of mating after European occupation. However, the presence of lineages of indisputable African assignation demonstrates that an aboriginal background still persists (<10%). On the basis of distribution and dating of some of these lineages we derived a genetic perspective of settlement processes of the archipelago in two stages, congruent with anthropological, archaeological and linguistic findings.



    Results and Discussion

    Haplogroup Distribution

    We have identified 20 different haplogroups (Table 2), of the 26 possible, in the sample from the Canary Islands being indicative of the informativeness of the markers selected for the study of this population. Relatedness and nomenclature of haplogroups are shown in Fig. 2
    based on those from the YCC (Y Chromosome Consortium,
    2002). Haplogroup R1(xR1a, R1b6, R1b8)
    is the most frequent in all seven islands, comprising 47%
    of the total sample (range 39.953.9%). This is, by far,
    also the most abundant haplogroup in the Iberian Peninsula
    (Bosch et al. 2001), reaching higher frequencies than
    in the Canarian population (P < 0.05, Mann-Whitney
    U-test). Excluding this haplogroup, several others are
    frequent (>10%), but only in some islands: haplogroup
    E3b2 in Tenerife, Gran Canaria and Fuerteventura; haplogroup
    I(xI1b2) in La Gomera; and haplogroup R1b8
    in El Hierro. Haplogroup E3b2, which has been assigned
    a Northwest African origin (Bosch et al. 2001),
    constitutes a clear African influence, reaching in some
    islands frequencies twice as high as those reported for the
    Iberian Peninsula (Bosch et al. 2001). On the other hand,
    haplogroups I(xI1b2) and R1b8 are European related
    lineages (Semino et al. 2000), the latter with an Iberian
    assignation (Hurles et al. 1999). Albeit at low frequencies,
    we have also detected the sub-Saharan haplogroup
    E3a in four of the seven islands. Considering the geographical
    location of the populations included in this
    analysis, haplogroup DE(xE3) may also be the result of
    C14 University College London 2003 Annals of Human Genetics (2003) 67,138152 143

    African influence. It must be noted that haplogroups E3aand DE(xE3) have not been detected in Iberian samples to date (Semino et al. 2000; Bosch et al. 2001). Also, it is striking that both an Iberian haplogroup (R1b8) and a sub-Saharan African haplogroup (E3a) were at
    their highest frequencies in the archipelago in El Hierro.

    The presence of some haplogroups of widespread distribution
    in Europe, in combination with others of clear
    Northwest and sub-Saharan African assignation, reflect
    the complex demographic patterns that have shaped the
    current Canarian population.

    Population Structure and Affinities

    Haplogroup distribution in the archipelago is heterogeneous
    (P = 0.001), although few (29%) pairwise comparisons
    gave results at a significant level (Table 3). Furthermore,
    when we carried out an AMOVA analysis,
    a low amount (0.3%) of variance was attributed to differences
    between populations within the archipelago.
    This value is 4.5 and 8 times lower than that obtained
    for the European and Northwest African populations
    considered here, respectively, although Canarian populations
    are distributed with a mean distance of 228 km,
    those of Europe with a mean of 587 km, and Northwest
    Africans with a mean of 668 km. This result could
    be perfectly explained by the way that European occupation
    occurred, with groups of people of mixed origin
    (Su´arez et al. 1988). This event, and subsequent
    gene flow, would have reduced the between island variance.
    Even though some neighbouring islands were
    also genetically related (Table 3), a Mantel test revealed
    that genetic and geographic distances are not correlated
    (r = 0.081, P = 0.612).

    Table 3

    FST distances (below diagonal) and exact probability values of differentiation (above diagonal) between Canarian populations

    El Hierro La Palma La Gomera Tenerife G. Canaria Lanzarote Fuerteventura
    El Hierro 0.637 0.008 0.008 0.089 0.042 0.353
    La Palma 0.012 0.273 0.295 0.886 0.525 0.307
    La Gomera 0.026 0.012 0.003 0.064 0.522 0.004
    Tenerife 0.023 0.007 0.020 0.997 0.075 0.019
    G. Canaria 0.027 0.009 0.026 0.002 0.249 0.164
    Lanzarote 0.020 0.005 0.010 0.008 0.010 0.120
    Fuerteventura 0.016 0.014 0.020 0.017 0.023 0.018
    P < 0.05 in bold.

    Table 4
    Percentages of variation among different geographical

    areas resulting from the AMOVA analysis
    Northwest sub-Saharan
    Europe Africa Africa
    El Hierro 0.005 0.344 0.371
    La Palma 0.000 0.319 0.371
    La Gomera 0.014 0.308 0.362
    Tenerife 0.001 0.299 0.380
    Gran Canaria 0.000 0.327 0.412
    Lanzarote 0.000 0.328 0.386
    Fuerteventura 0.015 0.258 0.361

    Europe — — —
    Northwest Africa 0.323
    Sub-Saharan Africa 0.373 0.503
    Canary Islands 0.003 0.279 0.342
    P > 0.05 in bold.

    When AMOVA was calculated between populations
    pooled by geographical areas (Table 4), the lowest, although
    significant, level of variation was observed in
    the European-Canarian comparison, being two orders
    of magnitude lower than the comparison with both
    African groups. This clearly indicates that Canarian
    populations have greater differences from Africans than
    from Europeans. Even so, the percentage of variance
    between Canarians and Africans is lower than percentages
    between Europeans and Africans, showing again
    an African paternal influence on the archipelago populations.
    Looking at each island, all are significantly
    different from both African groups, but only La Gomera
    and Fuerteventura are significantly different from the
    European pool (Table 4). More precisely, these two islands
    have the lowest differentiation values from both,
    Northwest and sub-Saharan Africans.
    Genetic affinities were also inspected from a MDS
    plot of FST genetic distances between populations
    144 Annals of Human Genetics (2003) 67,138152 C University College London 2003

    Y-Chromosome Variation in Canary Islands
    Figure 3



    Two-dimensional MDS plot relating Canarian and

    continental populations.
    (Fig. 3). The correlation between F



    ST and the new

    distances derived from a two-dimensional plot was
    very high (r = 0.971). In the same way, the obtained
    stress value (0.127) indicates that the chosen dimensionality
    is appropriate, and that a plot in a higher
    dimension is not necessary (http://www.analytictech.
    com/borgatti/mds.htm). Europeans, Northwest and
    sub-Saharan African populations constituted three different
    clusters. The Canarian populations formed a
    relatively tight cluster near the European group, but
    with some islands dispersed towards Northwest Africans.
    From the European group, clearly the general Iberians
    have the highest affinities with Canarian populations.
    Table 5
    Relative admixture contributions to the Canarian populations inferred from haplogroup frequencies

    Population Estimator Europe Northwest Africa sub-Saharan Africa FSTa
    El Hierro mL 0.957 ± 0.036 0.043 ± 0.036 0.003
    mY 0.959 ± 0.063 0.041 ± 0.063

    La Palma mL 0.961 ± 0.053 0.019 ± 0.049 0.021 ± 0.024 0.007
    mY 0.929 ± 0.054 0.051 ± 0.049 0.021 ± 0.027

    La Gomera mL 0.997 ± 0.057 0.003 ± 0.057 0.019
    mY 0.899 ± 0.050 0.092 ± 0.051 0.009 ± 0.024

    Tenerife mL 0.926 ± 0.041 0.074 ± 0.041 0.003
    mY 0.894 ± 0.044 0.097 ± 0.040 0.009 ± 0.013

    G. Canaria mL 0.897 ± 0.043 0.093± 0.041 0.010 ± 0.012 -0.005
    mY 0.885 ± 0.063 0.096± 0.059 0.019 ± 0.023

    Lanzarote mL 0.956 ± 0.046 0.035 ± 0.044 0.009 ± 0.015 0.003
    mY 0.940 ± 0.049 0.051 ± 0.046 0.009 ± 0.022

    Fuerteventura mL 0.832 ± 0.107 0.171 ± 0.107 0.006
    mY 0.877 ± 0.069 0.123 ± 0.069 — —

    Canary Is. Total mL 0.934 ± 0.030 0.059 ± 0.029 0.006 ± 0.008 0.003
    mY 0.910 ± 0.026 0.082 ± 0.026 0.008 ± 0.011

    a Variation not explained by the model (Long, 1991).

    Admixture Estimates
    In previous genetic approaches, to explain the colonisation
    of the Canary Islands admixture proportions have
    been inferred considering the extant people on the islands
    as a hybrid population with a Northwest African
    ancestry, contributed, most probably, by Berber aboriginal
    founders and, to a lesser degree, by sub-Saharan
    Africans introduced after the conquest as a result of slave
    trade. The other main contribution is from the European
    population that, since the beginning of the occupation,
    was steadily colonising the islands. However,
    the high paternal differentiation between these clusters
    of populations makes it possible to estimate their contributions
    to the current Canarian populations more accurately.
    Our admixture results (Table 5)were similar when
    mL or mY estimators were used, although African mY
    estimates always gave slightly higher values. For all comparisons
    the highest paternal contribution resulted from
    European descent. Northwest Africans would have also
    contributed significantly, but the sub-Saharan African
    contribution was almost negligible, excepting the case
    of El Hierro island. Differences between islands are evident,
    as the Northwest African contribution diminishes
    towards the westernmost islands, being insignificant
    in El Hierro. The opposite occurs for European
    contributions. As suggested from results on AMOVA
    C14 University College London 2003 Annals of Human Genetics (2003) 67,138152 145 analyses and genetic distances, the Europeans were the
    major contributors to the current Canarian paternal
    gene pool, explaining about 90% of its whole variability,
    while Northwest and sub-Saharan Africans contributed
    no more than 68%, and less than 1%, respectively
    (Table 5). Clearly, there is a sharp contrast between paternal
    admixture results and those from mtDNA and
    autosomal loci. As mentioned above, the higher African
    contribution to the Canarian mtDNA pool compared
    to the contribution estimated from the autosomal loci
    has been explained by an asymmetry of female and male
    aboriginal contribution to the current Canarian population
    (Pinto et al. 1996a; Flores et al. 2001a). During the
    Spanish conquest the European migration was constituted
    mainly of soldiers, who displaced autochthonous
    males by death or deportation, but mixed with aborigine
    females. A corollary of these results is that the
    aboriginal Y-chromosome contribution to the presentday
    Canarians has to be lower than those estimated
    from autosomal and mtDNA polymorphisms. This is
    exactly what we found with our experimental data. Although
    with stronger directional mating, similar results
    have been obtained for Amerind populations, which
    were also profoundly influenced by Iberian conquerors
    (Carvajal-Carmona et al. 2000; Sans, 2000; Carvalho-
    Silva et al. 2001).
    Regarding the portion of variance not explained by
    the admixture model (Table 5), and so due to genetic
    drift, the highest value, by one order of magnitude, was
    obtained for La Gomera, the second smallest island. Precisely,
    for mtDNA data La Gomera is the only island
    significantly different to the others and characterized by
    the highest frequency of the North African U6 cluster
    (Rando et al. 1998, 1999). In this regard, genetic drift
    could be responsible for the contrasting difference in
    African ancestry detected with maternal (51% of African
    lineages) and paternal markers (0.310% of African lineages).
    Alternatively, it could reflect the dramatic way
    the island was conquered, producing the strongest sexual
    asymmetry in the archipelago (Su´arez et al. 1988).

    Aborigine Settlement Process

    Three lineages deserve special attention due to their distribution
    in the archipelago and in populations from
    South western Europe and Africa: haplogroups J(xJ2),
    E3b1 and E3b2. Haplogroup J(xJ2) has been suggested
    to have originated in Middle East populations and spread
    to Europe with the dispersion of farming during the Neolithic
    period (Semino et al. 2000; Rosser et al. 2000;
    Bosch et al. 2001; Nebel et al. 2001). Its arrival to Northwest
    Africa could have occurred at the same time as in
    Mediterranean Europe (Bosch et al. 2001) or more recently,
    during the Islamization of the area (Nebel et al.
    2002). Nevertheless, it reaches higher frequencies in
    North Africa than in the Iberian Peninsula (Bosch et al.
    2001), being especially high in Ethiopians (Semino 2002). Although a clear North African origin has been
    assigned to haplogroup E3b1 (Bosch et al. 2001), it also
    characterizes most of the European YAP+haplogroups,
    as pointed out by Semino et al. (2002). Again, it reaches
    the highest frequencies in Ethiopians (Underhill et al.
    2000; Semino



    et al. 2002). Strikingly, both haplogroups

    are coincidentally distributed in the Canary Islands,
    reaching highest frequencies in western islands and decreasing
    eastwards (Fig. 1). Furthermore, they appeared
    in higher frequencies in the archipelago than in the European
    populations considered. On the other hand, for
    haplogroup E3b2 an unambiguous Northwest African
    origin has also been suggested (Bosch et al. 2001). It
    has been detected in Iberian populations (Bosch et al.
    2001; Flores, 2002), but never in frequencies so high as
    those reported for Northwest Africa. Moreover, its frequency
    in Canarians as a whole is nearly double those
    for the European populations considered, being particularly
    abundant in eastern islands (Fig. 1). At this point,
    there are at least three different explanations for the appearance
    of these three haplogroups in Canary Islands
    in such relatively high frequencies with respect to continental
    populations. First, they arrived in the archipelago
    with Iberian colonizers, as they are also influenced by
    Africans (Flores et al. 2000, 2001c; Bosch et al. 2001),
    and then augmented in frequency by genetic drift. Second,
    some could have come with Iberian populations
    and some directly from Northwest African influence.
    And third, they are an exclusive contribution from
    aboriginal inhabitants. Genetic drift could hardly
    explain a simultaneous increase of frequency for the
    three haplogroups, considering that they are precisely
    the three major haplogroups within North Africa (Underhill
    2000; Bosch et al. 2001). Furthermore,
    STR diversity within haplogroups by area (Table 6)
    146



    Annals of Human Genetics (2003) 67,138152 C University College London 2003

    Y-Chromosome Variation in Canary Islands
    Table 6



    STR diversity within haplogroups

    by area and mY haplotype contributions
    to the Canary Islands
    Haplogroup
    Population E3b1 E3b2 J(xJ2)
    Northwest Africa 1.83 ± 1.31 0.66 ± 0.51 1.12 ± 0.78
    Europe 0.93 ± 0.68 0.54 ± 0.46 0.58 ± 0.50
    Canary Islands 1.33 ± 0.86 0.75 ± 0.56 1.37 ± 0.87
    C/NWAa 0.168 ± 0.131 0.551 ± 0.677 0.334 ± 0.127
    C/Eb 0.832 ± 0.131 0.449 ± 0.677 0.666 ± 0.127
    a Contributions from Northwest Africa.

    b Contributions from Europe.

    argues against drift being the only factor responsible for
    that increase. Note that Canarian diversities, calculated
    from STR haplotypes (Appendix I), are always higher
    than those of Iberians and, in two instances, even than
    those of Northwest Africans. However, we must note
    that the particular comparison with Northwest African
    samples could be biased by the comparatively low number
    of samples used. We then applied mY estimator, using
    STR haplotypes and their molecular differences, to
    clarify the percentage of influence by which an area has
    contributed to Canarians for these haplogroups. The
    results (Table 6) supported a compound origin of these
    three haplogroups in the Canary Islands, making the
    second scenario more likely. Although J(xJ2) is not
    considered a genuine African marker, it seems that its
    presence in the Canary Islands has an important African
    cause. Even though it simplified the picture, we have
    considered haplogroups J(xJ2) and E3b1 as indicators
    of a movement of people coming from Southern parts
    of North Africa (Saharan marker), and haplogroup
    E3b2 as their Northwest African counterpart (Northwest
    African marker). In fact, the Saharan marker
    showed a trend of increasing frequencies westwards
    (rs = 0.714, P = 0.072, two-tailed test), and the contrary
    is observed for the Northwest African marker
    (rs = 0.857, P = 0.014, two-tailed test). Similar clinal
    patterns have been found for unlinked loci, such
    as mtDNA (Rando et al. 1999) and CD4/Alu haplotypes
    (Flores et al. 2001b), pointing to demographic
    events as a major cause, as selection would affect single
    genes. Even though the aboriginal population that
    occupied the archipelago was probably not a homogeneous
    group, the discrepant distribution of these haplogroups
    in relation to their distribution in Africa could
    be compatible with the hypothesis of more than one
    prehistoric settlement, particularly in the eastern islands
    (Onrubia-Pintado, 1987). Congruent with this hypothesis,
    cultural (Onrubia-Pintado, 1987; Navarro, 1992;
    Mart´ınez, 1996) and dialectal (Reyes-Garc´ıa, 2000) aborigine
    heterogeneities have been revealed within islands,
    supporting more than one arrival from Africa. Furthermore,
    linguistic investigation supports the idea that major
    dialectal influence in aborigines, common to all the
    islands, could have come from southern Algeria, but
    was also notably affected by Central Moroccan dialects
    (Reyes-Garc´ıa, pers. comm.). However, this possibility
    could not be confirmed in a previous mtDNA analysis
    (Rando et al. 1999), as the significant westward decrease
    of diversity and number of mtDNA African lineages
    was considered concordant to one dominant initial settlement
    from the African shore following a westward
    stepping-stone process.

    Dating the Aboriginal Colonisations

    Assuming that more than one aborigine settlement
    dispersed part of these three haplogroups in the
    archipelago, we tentatively tried to date those processes.
    Considering all the chromosomes from the Canary Islands,
    Europe and Northwest Africa, haplogroup J(xJ2)
    would have originated 3760 (CI 161013147) years
    ago, haplogroup E3b1 6060 (CI 259822221) years
    ago, and haplogroup E3b2 1840 (CI 7886433) years
    ago. We then calculated divergence percentages of haplogroups
    between the Canarian population and their
    parental populations. The results showed again congruent
    values for haplogroup J(xJ2) and E3b1, 52.7
    and 52.6% respectively, bolstering the hypothesis of
    their coincident dispersal in the Canarian archipelago.
    Translating into years, haplogroup J(xJ2) gave an age of
    2000 years and haplogroup E3b1 3200 years. These


    estimates match perfectly with the most ancient age of
    C human occupation in the Canary Islands as deduced

    from C14 dating (Onrubia-Pintado, 1987), and that deduced
    from mtDNA (Rando et al. 1999). The divergence
    for haplogroup E3b2 gave only 31.6%, which
    means 600 years, placing this colonization just before
    the European conquest. However, these coalescence
    time estimates must be interpreted with caution.
    They are highly influenced by demographic processes
    and are based on many assumptions of microsatellite
    mutation rates that could be erroneous (Stumpf & Goldstein,
    2001).

    In summary, our Y-chromosome analysis supports
    the hypothesis that the current paternal pool from the
    Canarian population is, to a great extent, of Iberian descent.

    The male aboriginal influence has been estimated
    to be less than 10%, whereas aboriginal mtDNA lineages
    represent 45%, reflecting the aggressiveway the islands
    were conquered. Nevertheless, with such a low number
    of aboriginal lineages, we detected and dated two prehistoric
    settlement processes, bolstered by osteological,
    cultural and linguistic data: the first one, with a Saharan
    substrate, arriving during the 1st millennium B.C., and
    the second, with a Northwest African ancestry, spreading
    just prior to the European conquest.

    http://www.geocities.com/vetinarilord/canary.pdf



  2. #2
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    Re: Origen genético de la población canaria

    Libros antiguos y de colección en IberLibro
    ¿La cultura íbero-mauriense aportó a las islas?

    Edito: Podéis borrar el mensaje, ya encontré la respuesta.
    Última edición por Xabel; Hace 1 semana a las 15:01

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