Category: Genetics
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E. O. Wilson against Hamiltonian inclusive fitness
There is a new paper in Nature which is a full frontal attack on the utility of William D. Hamilton’s inclusive fitness framework in explaining eusociality. Martin A. Nowak, Corina E. Tarnita, & Edward O. Wilson are the authors. Wilson is famous in large part for his authorship of Sociobiology: The New Synthesis, and is…
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The individual & social risks of cousin marriage
The map above shows the distribution of consanguineous marriages. As you can see there’s a fair amount of cross-cultural variation. In the United States there’s a stereotype of cousin marriage being the practice of backward hillbillies or …
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Just pushing buttons
Mike the Mad Biologist, whose bailiwick is the domain of the small, asks in the comments: I don’t mean to bring up a tangential point to the post, but why does the field of human genetics use PCA to visualize relationships? When I see plots like those shown here that have a ‘geometric pattern’ to…
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A thousand little adaptive platoons
Last week I took an intellectual road trip back nearly a century and explored the historical context and scientific logic by which R. A. Fisher definitively fused Mendelian genetics with quantitative evolutionary biology. In the process he helped birth the field of population genetics. While the genetics which we today are more familiar with begins at…
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Genetic variation within Africa (and the world)
Last year a paper came out in Science which made a rather large splash, The Genetic Structure and History of Africans and African Americans by Tishkoff et al. Since it’s more than a year old I recommend that those of you curious about the details of the paper and don’t have academic access go through…
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Desmond Tutu, Spaniards, and genetic distance
Since we’ve been talking about Fst a fair amount, I thought it might be nice to put it in some concrete graphical perspective. First, to review Fst in the genetic context measures the proportion of genetic variation which can be attributed to between population differences. To give a “toy” example if you randomly divided the…
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The flows and pulses of humanity
Dr. John Hawks points me to a review in BMC Biology, A question of scale: Human migrations writ large and small. It’s short, and of interest for the citations themselves. This a field in flux. One point which I think needs to be emphasized in relation to migration parameters is that there are going to…
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Which population is most genetically distant from Africans? Amerindians
Yesterday I stated that it was wrong to think of any non-African population as more genetically distant from Africans. Well, I was wrong. Sort of. This is obviously a case where I had a model in mind, and went looking for visuals which reinforced the story I was going to tell. As noted in the…
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Which population is most genetically distant from Africans?
A comment below: Razib, I don’t know much about genetics but is it true that these people of Melanesia are among the least related people (even more so than Europeans) to sub-saharan Africans genetically?? This is a common question. The typical scientifically curious intelligent person is generally aware that on the order of 100,000 years…
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Blondes of the ‘black islands’
Recently I was looking for images of the alpine biomes of the New Guinea highlands* and stumbled onto some intriguing, though not entirely surprising, set of photographs of individuals from Papua New Guinea. They were noteworthy because they manifested the conventional Melanesian physical type, but their hair had a blonde cast to it. For example,…
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Genetics is One: Mendelism and quantitative traits
In the early 20th century there was a rather strange (in hindsight) debate between two groups of biological scientists attempting to understand the basis of inheritance and its relationship to evolutionary processes. The two factions were the biometricians and Mendelians. As indicated by their appellation the Mendelians were partisans of the model of inheritance formulated…
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Native American ancestry in African Americans
That is, in the African American sample in the HapMap3 population set. I was just browsing the Admixture manual, and stumbled onto this plot: CEU = Utah Whites, and YRI = Yoruba. They should be familiar from the previous versions of the HapMap. MEX = Mexican Americans from Los Angeles. K = 3, three ancestral…
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Where writing is silent
In my post on Empires of the Word I observed that quite often the written record is silent on many matters which only language or genes tell us must have occurred. The Indo-Aryan character of the dominant language on the island of Sri Lanka seems to be a geographical anomaly in the least, but perhaps…
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Hybridization is like sex
One of the major issues which has loomed at the heart of biology since The Origin of Species is why species exist, as well as how species come about. Why isn’t there a perfect replicator which performs all the conversion of energy and matter into biomass on this planet? If there is a God the tree…
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PCA, Razib around the world (a little)
I have put up a few posts warning readers to be careful of confusing PCA plots with real genetic variation. PCA plots are just ways to capture variation in large data sets and extract out the independent dimensions. Its great at detecting population substructure because the largest components of variation often track between population differences,…
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Koreans, not quite the purest race?
PLoS One has a paper out on Korean (South) population genetics and phylogeography, Gene Flow between the Korean Peninsula and Its Neighboring Countries: SNP markers provide the primary data for population structure analysis. In this study, we employed whole-genome autosomal SNPs as a marker set (54,836 SNP markers) and tested their possible effects on genetic…
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Finland, still going its own way
Dienekes points to a new paper which highlights genetic variation in Fenno-Scandinavia (or in this case, Finland, Sweden and Denmark). A two-dimensional plot with the variation is pretty illustrative of what you’d expect: Finns are genetic outliers in Europe, to some extent even in comparison to Estonians, who speak a very similar language. But, I…
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Snap, phenotype, genotype and fitness
One of the main criticisms of the population genetic pillar of the modern evolutionary synthesis was that too often it was a game of “beanbag genetics”. In other words population geneticists treated genes as discrete independent individual elements within a static sea. R.A. Fisher and his acolytes believed that the average effect of fluctuations of…
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Diseases of the Silk Road
Nature has two papers out about something called “Behçet’s disease.” It has apparently also been termed the “Silk Road Disease”, because of its associations with populations connected to the Central Eurasian trade networks.Though described by Hippocrates 2,500 years ago, apparently it was “discovered” only in the 20th century by a Turkish physician. The reason that…