Category: Genetics
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Why overdominance probably isn’t responsible for much polymorphism
Hybrid vigor is a concept that many people have heard of, because it is very useful in agricultural genetics, and makes some intuitive sense. Unfortunately it often gets deployed in a variety of contexts, and its applicability is often overestimated. For example, many people seem to think (from personal communication) that it may somehow be…
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What if you call for a revolution and no one revolts?
When I was in 8th grade my earth science teacher explained he did not believe in Darwinism. He seemed a reasonable fellow so my first reaction was shock. My best friend at the time, who sat next to me, laughed, “Yeah, some people believe we’re descended from monkeys! Crazy, huh?” I didn’t really know what…
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The reality of cultural hitchhiking
The figure to the left is from a paper, The mountains of giants: an anthropometric survey of male youths in Bosnia and Herzegovina, which attempts to explain why the people from the uplands of the western Balkans are so tall. Anyone who has watched high level basketball, or perused old physical anthropology textbooks, knows that…
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Fisherianism in the genomic era
There are many things about R. A. Fisher that one could say. Professionally he was one of the founders of evolutionary genetics and statistics, and arguably the second greatest evolutionary biologist after Charles Darwin. With his work in the first few decades of the 20th century he reconciled the quantitative evolutionary framework of the school…
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Sexual selection decreasing difference
Sexual selection is often considered a driver of diversification of a lineage. I was introduced to the concept in Jared Diamond’s The Third Chimpanzee, where he suggested that racial differences in appearance might be due to sexual preference, following a suggestion originally made by Charles Darwin. Though sexual selection emerges now and then as a…
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The human extended phenotype
I think there is something to the hypothesis that we as a species are self-domesticated, but a new preprint really doesn’t change my probability up or down, Comparative Genomic Evidence for Self-Domestication in Homo sapiens. Notwithstanding my own participation in some comparative genomic work, a lot of the conclusions from this field are as clear and obvious to…
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Just because it’s not hereditary does not mean you can affect it
A comment below from John: Love to see a post about which human traits worth caring about are notable for having little or no hereditary component. It is all good and well to know what we cannot change, but it makes more sense to focus personally and as a parent on those things that aren’t…
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Why only one migrant per generation keeps divergence at bay
The best thing about population genetics is that because it’s a way of thinking and modeling the world it can be quite versatile. If Thinking Like An Economist is a way to analyze the world rationally, thinking like a population geneticist allows you to have the big picture on the past, present, and future, of…
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Why humans have so many pulse admixtures
The Blank Slate is one of my favorite books (though I’d say The Language Instinct is unjustly overshadowed by it). There is obviously a substantial biological basis in human behavior which is mediated by genetics. When The Blank Slate came out in the early 2000s one could envisage a situation in 2017 when empirically informed…
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Direct-to-consumer genomics, it’s back on!
The past three and a half years, and arguably longer, there has been something of a dark night passing over direct to consumer (DTC) personal genomics. The regulatory issues have been unclear to unfavorable. If you have read this blog you know 23andMe‘s saga with the Food and Drug Administration. It looks like 2017 DTC is…
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Sex bias in migration from the steppe (revisited)
Last fall I blogged a preprint which eventually came out as a paper in PNAS, Ancient X chromosomes reveal contrasting sex bias in Neolithic and Bronze Age Eurasian migrations. The upshot is that the authors found that there was far less steppe ancestry on the X chromosomes of Bronze Age Central Europeans than across the whole…
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How Tibetans can function at high altitudes
About seven years ago I wrote two posts about how Tibetans manage to function at very high altitudes. And it’s not just physiological functioning, that is, fitness straightforwardly understood. High altitudes can cause a sharp reduction in reproductive fitness because women can not carry pregnancies to term. In other words, high altitude is a very strong selection…
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List of top 10 evolutionary biologists in history
What is your list of the top 10 evolutionary biologists in history? I’m asking because this came up in a discussion with a friend. Obviously the composition of the list will have to do with disciplinary bias and geography and history (there are Russian population geneticists from the 20th century who should be more famous…
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How Indians are a lot like Latin Americans
Pretty much any person of Indian subcontinental origin in the United States of a certain who isn’t very dark skinned has probably had the experience of being spoken to in Spanish at some point. When I was younger growing up in Oregon I had the experience multiple times of Spanish speakers, probably Mexican, pleading with…
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Ancestry inference won’t tell you things you don’t care about (but could)
The figure above is from Noah Rosenberg’s relatively famous paper, Clines, Clusters, and the Effect of Study Design on the Inference of Human Population Structure. The context of the publication is that it was one of the first prominent attempts to use genome-wide data on a various of human populations (specifically, from the HGDP data set)…
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Your ancestry inference is precise and accurate(ish)
For about three years I consulted for Family Tree DNA. It was a great experience, and I met a lot of cool people through that connection. But perhaps the most interesting aspect was the fact that I can understand the various pressures that direct-to-consumer genomics firms face from the demand side. The science is one…
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Genomics Is Not Magic, There Is No Magic
MIT Technology Review has an article up, Do Your Family Members Have a Right to Your Genetic Code?, which is now part of the genomics-human-interest-piece genre you see regularly. Here you have the exemplar of this sort of narrative: what do you do whe…
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Afro-Asiatic and Eurasian Backflow
If you follow Y genealogy you know that the distribution of R1ba2 exhibits a peculiar pattern. R1b is the most common haplgroup in Western Eurasia, and shares a deep common ancestry with R1a. It seems to have risen to high frequencies in Europe only du…
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The Species Barriers Between Neanderthals and Anatomically Modern Humans
A new paper in The American Journal of Humans Genetics, The Divergence of Neandertal and Modern Human Y Chromosomes, reports on possible reasons why we don’t see Y chromosomes in modern humans from this archaic lineage, despite exhibiting detectable le…
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The species barriers between Neanderthals and anatomically modern humans
A new paper in The American Journal of Humans Genetics, The Divergence of Neandertal and Modern Human Y Chromosomes, reports on possible reasons why we don’t see Y chromosomes in modern humans from this archaic lineage, despite exhibiting detectable levels of autosomal admixture. As you might recall the clear lack of deep branching Y and…