Post by Admin on Feb 24, 2022 2:22:47 GMT
Figure 3. ADMIXTURE Plot
ADMIXTURE analysis at K = 10 of the five Guanche individuals that yielded the highest genome coverage (0.21× to 3.93×) and a selection of modern samples from the Human Origins dataset together with published ancient genomes. (See Figure S3 for complete admixture plot and references.) Within the Guanches cluster, the five individual bars represent (from left to right) gun005, gun008, gun011, gun012, and gun002.
The results of the ADMIXTURE analysis furthermore show that the Guanches carried early European farmer (EEF)-like ancestry; this ancestry component is widespread (though at varying proportions) in present-day North Africans and Middle Easterners but rare or largely absent in some Berber populations (Figure 3). The EEF component is strongly associated with early Neolithic farmers from Anatolia and Europe (as well as present-day Sardinians), hinting at a possible link between present-day North Africans and the expansion of Neolithic culture through the Mediterranean [31, 32, 33], though it could also reflect post-Neolithic gene flow among Mediterranean groups [34]. The Guanches also appear to have carried varying proportions of Middle Eastern ancestry, best represented by the HO Bedouin_B population.
We also note that one Guanche individual (gun005) carried a greater proportion of hunter-gatherer (HG)-like ancestry than the other individuals, possibly suggesting low-level gene flow from a European source that predates the European conquest. Although our results are overall consistent with an origin from a single ancestral population in North Africa, the possible small-scale introgression from other sources postdating the earliest settling is consistent with archaeological finds of Phoenician-Punic amphora in Buena Vista (Lanzarote) and Roman amphora fragments retrieved from El Bebedero (Lanzarote), indicating that the islands (and local islanders) were in at least sporadic contact with other peoples and cultures prior to the European colonization in the 15th century CE [5].
The Europeans who colonized the islands in the 15th century CE found that the Guanches shared a similar language and material culture centered on goat herding and small-scale cultivation of domesticated crops, despite lacking boats and the ability to navigate the surrounding sea [1, 4, 5]. In the years following the European colonization, a great number of Guanches were killed in several wars throughout the islands [35]. Survivors integrated into the colonizing populations and left behind a genetic as well as cultural imprint on today’s population, although the degree to which the former has shaped the gene pool of modern Canary Islanders remains unclear [6, 8, 26]. Since the ADMIXTURE analysis reveals that present-day Canary Islanders possess a small degree of North African ancestry, we performed admixture f3 tests [19, 25] to determine whether modern Canary Islanders (n = 2 in the HO dataset) can be modeled as a mix between Guanches and a Western European population from the Human Origins panel. f3 was significantly negative (Z < −2) for 12 out of 26 populations tested as second source (Table S3). The lowest f3 value was obtained when modeling Canary Islanders as a mix of Guanches and modern-day Scots. Next, we used f4 ratios [19, 25] to estimate the contribution of Guanches to modern Canary Islanders. The estimates range from 16.7% (SE 4.96%) when using Spanish_Murcia as the European source to 31.3% (SE 3.89%) when using modern Norwegians. This difference is presumably due to modern Spaniards showing higher affinities to North Africans than Northern Europeans [34]. However, other European source populations provided intermediate values, such as a Basque population from Spain (27.2%, SE 4.92%) (Table S3). These results are smaller than the estimates of genetic contribution obtained using mitochondrial DNA (42%–73%) [6] but higher than estimates based on Y chromosome data (17%) [8], suggesting that the male Guanche contribution to modern-day Canary Islanders is lower than the female Guanche contribution. This may have been due to the violent process of colonization by the Europeans, which led to the death of a proportionally greater number of Guanche males than females [8, 35]. However, we caution that Canary Islanders in the HO dataset may not be representative of all Canary Islands, not only because of the small sample size (n = 2) but also because previous studies have shown significant differences in the relative proportion of mitochondrial ancestry between the different islands [17].
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