Latin America is not panmixia
A new provisional paper, Ancestry-related assortative mating in latino populations. Here are the results:
Using 104 ancestry informative markers, we examined spouse correlations in genetic ancestry for Mexican spouse pairs recruited from Mexico City and the San Francisco Bay Area, and Puerto Rican spouse pairs recruited from Puerto Rico and New York City. In the Mexican pairs, we found strong spouse correlations for European and Native American ancestry, but no correlation in African ancestry. In the Puerto Rican pairs, we found significant spouse correlations for African ancestry and European ancestry but not Native American ancestry. Correlations were not attributable to variation in socioeconomic status or geographic heterogeneity. Past evidence of spouse correlation was also seen in the strong evidence of linkage disequilibrium between unlinked markers, which was accounted for in regression analysis by ancestral allele frequency difference at the pair of markers (European versus Native American for Mexicans, European versus African for Puerto Ricans). We also observed an excess of homozygosity at individual markers within the spouses, but this provided weaker evidence, as expected, of spouse correlation. Ancestry variance is predicted to decline in each generation, but less so under assortative mating. We used the current observed variances of ancestry to infer even stronger patterns of spouse ancestry correlation in previous generations.
The correlations are to the left. An interesting point is that the correlations of total genome content seem too high to be explained by assortative mating for salient physical features (skin color, hair form, etc.) alone. From the text:
Another possibility involves physical characteristics, such as skin pigment, hair texture, eye color, and other physical features. Certainly, these traits are correlated with ancestry and are likely to be factors in mate selection. However, the spouse correlation for these traits must be high and the correlation of these traits with ancestry must also be high to explain the observed ancestry correlations….…
If the spouse trait correlation is 0.6 (a reasonably high value), then for a spouse ancestry correlation of 0.3 (Puerto Ricans), the trait-ancestry correlation is 0.7; for a spouse ancestry correlation of 0.4 (Mexicans), the trait-ancestry correlation is 0.8. Previous studies on assortative mating in Latin American groups have retrieved correlation coefficients of 0.29 to 0.46 for education level, 0.48 for skin reflectance, 0.07 to 0.18 for eye and hair color, and 0.16 to 0.24 for different anthropometric measurements
As noted above, they controlled for SES and geography, and the correlation remains. Looking at the correlations within the genomes of these individuals they also inferred that assortative mating in the past was actually greater than it is today (they also have a historical citation which suggests this). I wonder of the correlation of ancestry is due to sorting by many traits which are subtle and nuanced, and relatively difficult to capture in surveys of the coarse salient traits are used to categorize phenotypic races. Looking at many traits, as opposed to a few, and one would have a better sense of total genome content. When it comes to mating one might look to a range of traits which in other circumstances are not noted, or fall below the threshold of reflective awareness. I’m assuming there might be something here which is Gestalt and subconscious. Kind of like the various studies which attempt to correlate mate preferences by HLA polymorphism.
Labels: Genetics, Population genetics
also related
Ethnicity can be a means by which people identify themselves and others. This type of identification mediates many kinds of social interactions and may reflect adaptations to a long history of group living in humans. Recent admixture in the US between groups from different continents, and the historically strong emphasis on phenotypic differences between members of these groups, presents an opportunity to examine the degree of concordance between estimates of group membership based on genetic markers and on visually-based estimates of facial features. We first measured the degree of Native American, European, African and East Asian genetic admixture in a sample of 14 self-identified Hispanic individuals, chosen to cover a broad range of Native American and European genetic admixture proportions. We showed frontal and side-view photographs of the 14 individuals to 241 subjects living in New Mexico, and asked them to estimate the degree of NA admixture for each individual. We assess the overall concordance for each observer based on an aggregated measure of the difference between the observer and the genetic estimates. We find that observers reach a significantly higher degree of concordance than expected by chance, and that the degree of concordance as well as the direction of the discrepancy in estimates differs based on the ethnicity of the observer, but not on the observers’ age or sex. This study highlights the potentially high degree of discordance between physical appearance and genetic measures of ethnicity, as well as how perceptions of ethnic affiliation are context-specific. We compare our findings to those of previous studies and discuss their implications.
I truly didn’t expect that there would not be an Amerindian ancestry on the spouse correlations, as there have been studies who have founded Strong Native American MTDNA in Puerto Ricans, so it should have been shown Native American ancestry in this spouse study but it didn’t, is there any explanation why?