ما مدى امتزاج الإسبان بالعرب؟ علم الوراثة يجيبكم..
نشرت في: 08/02/2019 - 14:16آخر تحديث: 11/02/2019 - 05:55
مشاهدة المرفق 431996
إعداد:
لطالما تساءل الكثير من المولعين بقصص الأندلس والحكم الإسلامي في شبه الجزيرة الإيبيرية عن مدى امتزاج الإسبان بالعرب والأمازيغ القدامى. الأسبوع الماضي، كشفت دراسة نشرت في مجلة "نيتشر" وأنجزها باحثون في جامعتي أوكسفورد البريطانية وسنتياغو دي كومبوستيلا الإسبانية عن معلومات قيمة حول بصمة المغاربة الجينية.
he cultural and linguistic impact of Muslim rule in Iberia is well-documented, but the historical record is limited in its ability to inform about the extent, timing and geographic spread of genetic mixing between immigrants and indigenous Iberians over several centuries after the initial conquest
. Previous genetic studies have reported signals of admixture from sub-Saharan Africa and/or north Africa into Iberia at some point in the past
,
,
,
,
. However, estimates of the timing of this admixture vary greatly, from as long as 74 generations ago (~100 BC)
to 23 generations ago (~1330 CE)
. Estimates of overall mean proportions of African-like DNA in the Iberian Peninsula also vary, ranging from 2.4
to 10.6%
. Differences within Iberia have also been reported
,
, based on comparisons between sampled regions, with higher fractions observed in western regions of Iberia (e.g. 21.7% in Northwest Castile
) and lower fractions in the north-east (e.g. 2.3% in Cataluña
). Estimates of the timing and extent of admixture tend to vary depending on the reference populations assumed to represent the ancestral mixing groups (e.g. Moroccan
or Saharawi
), as well as heterogeneity in the ancestral make-up of the modern-day Iberian samples used in the analysis.
We also detect a genetic footprint of the Muslim conquest, and subsequent centuries of Muslim rule. Following the arrival of an estimated 30,000 combatants
, a civilian migration of unknown numbers of people occurred, thought to be mainly Berbers from north Morocco and settling in many parts of the peninsula
. Our analysis confirms and refines previous findings
,
,
of a substantial and regionally varying genetic impact, narrowing to a period spanning < 400 years. Crucially, unlike previous genetic studies of admixture in Iberia
,
,
, we avoid strong assumptions about the genetic make-up of the historical admixing groups. Instead of specifying in advance the modern-day sources that we assume best represent the historical populations that came together in the past, we infer the best mixture of modern-day populations from a large set of possible groups. Our GLOBETROTTER results suggest that amongst the six potential African populations in our study, the best match to the predominant group involved in the actual admixture event is north-west African. Moreover, admixture mainly, and perhaps almost exclusively, occurred within the earlier half of the period of Muslim rule (Fig.
). Within Spain, north African ancestry occurs in all groups, although levels are low in the Basque region and in a region corresponding closely to the 14th-century Crown of Aragon (compare Figs
c,
). Therefore, although genetically distinct
,
, north African-like ancestry in the Basque region could be explained through genetic interactions between the Basque groups and other parts of Spain within the past 1300 years.
Perhaps surprisingly, north African ancestry does not reflect proximity to north Africa, or even regions under more extended Muslim control. The highest amounts of north African ancestry found within Iberia are in the west (11%) including in Galicia, despite the fact that the region of Galicia as it is defined today (north of the Miño river), was never under Muslim rule
and Berber settlements north of the Douro river were abandoned by 741. This observation is consistent with previous work using Y-chromosome data
. We speculate that the pattern we see is driven by later internal migratory flows, such as between Portugal and Galicia, and this would also explain why Galicia and Portugal show indistinguishable ancestry sharing with non-Spanish groups more generally. Alternatively, it might be that these patterns reflect regional differences in patterns of settlement and integration with local peoples of north African immigrants themselves, or varying extents of the large-scale expulsion of Muslim people, which occurred post-
Reconquista and especially in towns and cities
,
.
