Wednesday, January 24, 2018

The Genetics Of Conversos In Latin America

Latin American was colonized just as Jews were being expelled from Spain, and many converted to Christianity and migrated to the New World even though this was illegal. A new genetic study demonstrates that these "Conversos" made up a larger share of early migrants to Latin America than had generally been believed. The rest of the findings generally support the prevailing paradigm and historical record of migration to Latin America.

The paper also demonstrates the unsurprising finding that your genetic ancestry impacts your physical appearance.

A deeper issue is what this means to people emotionally and personally (which, of course, a genetics paper can't answer). While some Conversos maintained a connection to their ancestral religion, especially at first, five hundred years later, the vast majority of them let those ties fade away and assimilated into Latin American Catholicism, and in most cases, they did so before the lives of the people recorded in the oldest available recollections and genealogical records available to modern Latin Americans.

As a Brazilian or Mexican with hundreds of years of Catholic ancestors, who is now Catholic or Pentecostal or secular, who has never observed any aspect of a Jewish ancestry, does it matters that you have Sephardic Jewish ancestry?

If so, what does it mean to you and what does the prevalence of this ancestry across Latin America means to your whole society's understanding of itself and its past?

The paper is also a good quantitative example of the extent to which population structure decays over time. This happens significantly more slowly than it would under the hypothesis of panmixia which would have caused Sephardic ancestry to almost reach fixation in these countries. But, the decay of population structure is still strong enough of a tendency that only 23 people in a sample of 6,500 who did not have grandparents or more recent a ancestors who immigrated to Latin America (there were 19 recent immigrants in the sample) were more than 25% Sephardic, despite the fact that about 1500 people in the sample had a least 5% Sephardic ancestry. The average percentages of Sephardic ancestry by country in the study were: Brazil (1%), Chile (4%), Colombia (3%), Mexico (3%) and Peru (2%).

Razib Khan also has a decent post on the paper including its broader social importance.

The abstract from the paper, a citation to it, and some excerpts from the body text of the paper, with my emphasis added, follows below the fold.

Historical records and genetic analyses indicate that Latin Americans trace their ancestry mainly to the admixture of Native Americans, Europeans and Sub-Saharan Africans. Using novel haplotype-based methods here we infer the sub-populations involved in admixture for over 6,500 Latin Americans and evaluate the impact of sub-continental ancestry on the physical appearance of these individuals. 
We find that pre-Columbian Native genetic structure is mirrored in Latin Americans and that sources of non-Native ancestry, and admixture timings, match documented migratory flows. We also detect South/East Mediterranean ancestry across Latin America, probably stemming from the clandestine colonial migration of Christian converts of non-European origin (Conversos). Furthermore, we find that Central Andean ancestry impacts on variation of facial features in Latin Americans, particularly nose morphology, possibly relating to environmental adaptation during the evolution of Native Americans.

From the body text:
SOURCEFIND analysis extends these results by enabling the inference of 25 Native American ancestry components across Latin America, resulting in a high-resolution picture of Native variation in the region and emphasizing the “genetic continuity” of pre-Columbian and admixed populations across the Americas. In addition, SOURCEFIND distinguishes between closely-related ancestry components from the Iberian Peninsula, as well as from the East and South Mediterranean (including individuals self-identified as Sephardic; i.e. Iberian Jews). The distribution of European ancestry in the CANDELA sample shows a sharp differentiation between Brazil and the Spanish American countries. In Brazil the predominant European sub-component matches mostly the Portugal/West-Spain reference group while in Mexico, Colombia, Peru and Chile mostly Central/South-Spanish ancestry is inferred. This differentiation matches the colonial history, Portuguese migration having concentrated in Eastern South America while the Spanish settled mainly in Central America and Western South America. The relatively small contribution inferred for the Basque and Catalan agrees with historical information documenting that Spanish migrants to America originated mainly in Southern and Central Spain. In addition, the Brazilian sample shows substantial Italian and German ancestry, and these components concentrate in the South of the country. This pattern is consistent with the documented migration to Southern Brazil of large numbers of Germans and Italians in the late 19th century.
Inferred dates for events involving Iberian components had a median of 10 generations (IQR=7-13), consistent with other estimates for admixture in Latin America. Noticeably, individuals with more recent inferred dates of admixture have greater Native ancestry, consistent with continuing admixture between admixed Latin Americans and unadmixed Natives, possibly as a result of the decline in Iberian immigration after the mid17th century, concomitant with the demographic recovery of neighboring Native American populations. Admixture involving the German or Italian components have a significant skew towards more recent dates than admixture involving Iberians (Wilcoxon ranksum test one-sided p-value=3×10-8), consistent with the relatively recent arrival of Germans and Italians.

SOURCEFIND finds that Sephardic/East/South Mediterranean ancestry is detectable in all the countries sampled: Brazil (1%), Chile (4%), Colombia (3%), Mexico (3%) and Peru (2%). Altogether, ~23% of the CANDELA individuals show >5% of such ancestry and in these individuals SOURCEFIND infers this ancestry to be mostly Sephardic (7.3%), with smaller non-Sephardic East Mediterranean (3.9%) and non-Sephardic South Mediterranean (1%) contributions. Individuals with Sephardic/East/South Mediterranean ancestry were detected across Latin America. GLOBETROTTER estimates for the time since Sephardic/East/South Mediterranean admixture were not significantly different from those involving Iberian sources (Wilcoxon rank-sum test one-sided pvalue>0.1). It is possible that outliers with particularly high values of Sephardic/East/South Mediterranean ancestry are descendants from recent non-European immigrants. For 19 of 42 individuals with >25% Sephardic/East/South Mediterranean ancestry genealogical information (up to grandparents) identified recent ancestry in the Eastern Mediterranean. However, no recent immigration was documented for Colombians with >5% Sephardic ancestry, despite these individuals showing the highest estimated Sephardic ancestry across countries (10% on average). 
Jewish communities existed in Iberia (Sepharad) since roman times and much of the peninsula was ruled by Arabs and Berbers for most of the Middle Ages, by the end of which large Sephardic communities had developed. Genetic studies have detected North and East Mediterranean ancestry in the current Spanish population, as well European admixture in the Sephardim. The estimates of North and East Mediterranean (including Sephardic) ancestry in Latin Americans obtained here represent values over and above those present in our sampled present-day Spanish individuals, suggesting migration of individuals with higher levels of such ancestry to Latin America. Columbus’ arrival to the New World in the late 15th century coincided with the expulsion of Jews from Iberia, with the non-Christians remaining being forced to convert to Christianity. Although these Conversos were forbidden from migrating to the colonies, historical records document that some individuals made the journey, in an attempt to avoid persecution. Since this was a clandestine process, the extent of Converso migration to Latin America is poorly documented. Genetic studies have provided suggestive evidence that certain Latin American populations, arguably with a peculiar history, could have substantial Converso ancestry. Our findings indicate that the genetic signature of Converso migration to Latin America is substantially more prevalent than suggested by these special cases, or by historical records.

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