Razib Khan

Category: Genetics

  • 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…

  • How genetics are rewriting the history of the Caribbean

    Over the past century history has been approached from many different angles, despite the stereotype of scholars haunting dusty archives. Adventurers once called antiquarians became archaeologists, and inspired the fictional Indiana Jones. Today it is the turn of the geneticists to put their stamp upon history. By tracing patterns of variation they gain insights as to the…

  • Selection happens; but where, when, and why?

    One of the secondary issues which cropped up with Nina Davuluri winning Miss America is that it seems implausible that someone with her complexion would be able to win any Indian beauty contest. A quick skim of Google images “Miss India” will make clear the reality that I’m alluding to. The Indian beauty ideal, especially…

  • Selection happens; but where, when, and why?

    One of the secondary issues which cropped up with Nina Davuluri winning Miss America is that it seems implausible that someone with her complexion would be able to win any Indian beauty contest. A quick skim of Google images “Miss India” will make clear the reality that I’m alluding to. The Indian beauty ideal, especially…

  • Indo-Aryan Assimilation Theory (AAT)

    See my post and Zack Ajmal’s. Also, in case I didn’t make it clear enough in the post: I think that post-Indo-Aryan incursions were probably non-trivial. I now lean toward the proposition that the Jat populations of northwest India and … Continue reading →

  • Why the future won’t be genetically homogeneous

    While reading The Founders of Evolutionary Genetics I encountered a chapter where the late James F. Crow admitted that he had a new insight every time he reread R. A. Fisher’s The Genetical Theory of Natural Selection. This prompted me to put down The Founders of Evolutionary Genetics after finishing Crow’s chapter and pick up…

  • Mitochondrial Eve: a de facto deception?

    The above image, and the one to the left, are screenshots from my father’s 23andMe profile. Interestingly, his mtDNA haplogroup is not particularly common among ethnic Bengalis, who are more than ~80% on a branch of M. This reality is clear in the map above which illustrates the Central Asian distribution my father’s mtDNA lineage.…

  • The causes of evolutionary genetics

    A few days ago I was browsing Haldane’s Sieve,when I stumbled upon an amusing discussion which arose on it’s “About” page. This “inside baseball” banter got me to thinking about my own intellectual evolution. Over the past few years I’ve been delving more deeply into phylogenetics and phylogeography, enabled by the rise of genomics, the…

  • We are Nature

    There’s an interesting piece in Slate, The Great Schism in the Environmental Movement, which seems to be a distillation of trends which have been bubbling within the modern environmentalist movement for a generation now (I’ve read earlier manifestos in a similar vein). I can’t assess the magnitude of the shift, but here’s the top-line: But…

  • A lighter shade of brown: Dan MacArthur, look east or south!

    In the post below I offered up my supposition that Dan MacArthur’s ancestry is unlikely to be Northwest Indian, which precludes a Romani origin for his South Asian ancestry. Indeed this is almost certainly so, Dienekes Pontikos followed up my crude analyses with IBD-sharing calculations (IBD = ‘identity by descent,’ which is basically what you…

  • Don’t wait to have children!

    The New Republic has a piece up, How Older Parenthood Will Upend American Society, which won’t have surprising data for readers of this weblog. But it’s nice to see this sort of thing go “mainstream.” My daughter was born when her parents were in their mid-30s, so I know all the statistics. They aren’t good…

  • We don’t know why Ethiopians breathe easy

    Most people are aware that altitude imposes constraints on individual performance and function. Much of this is flexible; athletes who train at high altitudes may gain a performance edge. But over the long term there are costs, just as there are with computers which are ‘overclocked.’ This is the point where you make the transition…

  • Is Daniel MacArthur ‘desi’?

    My initial inclination in this post was to discuss a recent ordering snafu which resulted in many of my friends being quite peeved at 23andMe. But browsing through their new ‘ancestry composition’ feature I thought I had to discuss it first, because of some nerd-level intrigue. Though I agree with many of Dienekes concerns about…

  • The origins of the Romani determined definitively

    In many cases there are questions of a historical and ethnographic nature which are subject to controversy and debate. Scholarly arguments are laid out, and further dispute ensues. For decades progress seems fleeting, as one hypothesis is accepted, only to be subject to later revision. This sort of pattern gives succor to the most cynical…

  • TreeMix: Who were the West Eurasian ancestors of Ethiopians?

    One of the primary concerns/questions I had about Luca Pagani’s paper on the genetic origin of Ethiopians is that he found that their West Eurasian ancestor was closer to Levantine than Arabian. I was confused by this because on model-based clustering (e.g., Admixture) when you push down to a fine level of granularity you always…

  • Layering genetic histories

    As a follow up to my post from yesterday, I decided to run TreeMix on a data set I happened to have had on hand (see Inference of Population Splits and Mixtures from Genome-Wide Allele Frequency Data for more on TreeMix). Basically I wanted to display a tree with, and without, gene flow. The technical…

  • Africa’s hidden people hold the keys to the past

    I mentioned this in passing on my post on ASHG 2012, but it seems useful to make explicit. For the past few years there has been word of research pointing to connections between the Khoisan and the Cushitic people of Ethiopia. To a great extent in the paper which is forthcoming there is the likely…

  • Northern Europeans and Native Americans are not more closely related than previously thought

    A new press release is circulating on the paper which I blogged a few months ago, Ancient Admixture in Human History. Unlike the paper, the title of the press release is misleading, and unfortunately I notice that people are circulating it, and probably misunderstanding what is going on. Here’s the title and first paragraph: Native…

  • Northern Europeans and Native Americans are not more closely related than previously thought

    A new press release is circulating on the paper which I blogged a few months ago, Ancient Admixture in Human History. Unlike the paper, the title of the press release is misleading, and unfortunately I notice that people are circulating it, and probably misunderstanding what is going on. Here’s the title and first paragraph: Native…

  • Agriculture, South India, Genetics

    Population Differentiation of Southern Indian Male Lineages Correlates with Agricultural Expansions Predating the Caste System: Previous studies that pooled Indian populations from a wide variety of geographical locations, have obtained contradictory conclusions about the processes of the establishment of the … Continue reading →

Razib Khan