Admixture Studies

I had commented on admixture mapping before, but I was unaware of how advanced the techniques had become. For a semi-technical overview:

Winkler et al., 2010. Admixture Mapping Comes of Age

Admixture mapping is based on the hypothesis that differences in disease rates between populations are due in part to frequency differences in disease-causing genetic variants. In admixed populations, these genetic variants occur more often on chromosome segments inherited from the ancestral population with the higher disease variant frequency. A genome scan for disease association requires only enough markers to identify the ancestral chromosome segments; for recently admixed pop- ulations, such as African Americans, 1,500–2,500 ancestry-informative markers (AIMs) are sufficient. The method was proposed over 50 years ago, but the AIM panels and statistical methods required have only recently become available. Since the first admixture scan in 2005, the genetic bases for a range of diseases/traits have been identified by admix- ture mapping. Here, we provide a historical perspective, review AIM panels and software packages, and discuss recent successes and unexpected insights into human diseases that exhibit disparate rates across human populations.

When it comes to disease disparities (e.g. vascular disease and cancer), average phenotypic differences are identified using national databases. Those for which there is a statistically significant difference are candidates for research. Here’s a typical writeup:

Obesity is about 1.5-fold more prevalent in African Americans than European Americans. To determine whether genetic background may contribute to this observed disparity, we scanned the genomes of African Americans, searching for genomic regions where obese individuals have a difference from the average proportion of African ancestry. By examining genetic data from more than 15,000 African Americans, we show that the proportion of European ancestry is inversely correlated with BMI. In obese individuals, we detect two loci with increased African ancestry on chromosome X (Xq13.1 and Xq25) and one locus with increased European ancestry on chromosome 5 (5q13.3). The 5q13.3 and Xq25 regions both contain genes that are known to be involved in appetite regulation. Our results suggest that genetic factors may contribute to the difference in obesity prevalence between African Americans and European Americans. Further studies of the regions may identify the causative variants affecting susceptibility to obesity

It’s simply amazing that, in light of the research being conducted, there are still environmentalists who argue that “race isn’t a useful biological category” or that the Natural History Museum would have the audacity to have an exhibit which “seeks to show that race is not rooted in biology.”

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4 Responses to Admixture Studies

  1. What is nevertheless encouraging here is that 99% of the comments in the Smithsonian blog listed in this post belong to people who clearly see through the canard and are fed up with the propaganda.

    Please consider following and/or blogrolling us over at :


    – Arturo

  2. Kiwiguy says:

    You can get an idea of the environmentalist perspective on this thread.

    • Chuck says:

      Ya, I was on that thread for a while but that Tiel guy just wouldn’t concede that he was wrong. Hey, why don’t you spend some time and collect some of the pro-race arguments/ citations and post them somewhere so that the rest of us can have easy referenced?

  3. Kiwiguy says:

    Tiel is a classic example of a rabid, hysterical, brain washed anti-racist.

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