razib | August 5, 2006I've decided to jot down some simple* formalisms which I can refer new readers to on this website. So today....
You know that if you have a novel mutation within a population, its probability of fixation if it is neutral is:
1/(2N), where N = effective population, in a neutral scenario where the mutation confers neither advantage or disadvantage. So in a population of 100, a new mutant has a 1 out of 200 chance of fixation, going from 0.5% in the initial generation, to 100% in the generation of fixation. In a population of 1000, a new mutation has a .05% chance of fixation, and so forth.…
razib | August 5, 2006Most of you have likely heard of the paper out in The Proceeding of the Royal Society, Can the common brain parasite, Toxoplasma gondii, influence human culture?. Here is the relevant section from the abstract:
Toxoplasma gondii, explains a statistically significant portion of the variance in aggregate neuroticism among populations, as well as in the 'neurotic' cultural dimensions of sex roles and uncertainty avoidance. Spurious or non-causal correlations between aggregate personality and aspects of climate and culture that influence T. gondii transmission could also drive these patterns. A…
razib | August 3, 2006People often talk about random genetic drift. Like sexual selection it is the deus ex machina of choice when you are shit out of luck in regards to hypotheses. And yet though it looms large in our minds R.A. Fisher dismissed it as an important evolutionary force. Sewall Wright in his Shifting Balance Model tended to emphasize the interactions of genes more than the random fluctuation of frequency as such. Drift only came into its own with the rise of Neutral Theory and molecular evolution. In any case, I'm going throw out an algebraic relation out there that I think is important to keep…
razib | August 3, 2006Over at my other weblog I have a new 10 questions up, this one for Matthew Stewart, author of two popular books on history and philosophy which I have enjoyed, The Truth About Everything and The Courtier and the Heretic. Stewart's responses have been among the most entertaining so far in this series, and I especially liked his response to #5 (big surprise, because it aligns closely with my own opinion, and that my dear is an elementary proposition).
razib | August 2, 2006Over at Nation Building I make a plea for methodological rationality. But more importantly, I point to Noah Millman.
razib | August 2, 2006Since I'm the 6th person to point to this, check out a new Science Blog, Smooth Pebbles. I'm expecting readers to come up with a real cool header....
razib | August 2, 2006I have talked about the problems that may occur because of long term societal inbreeding in the past. In short, in a society that is predominantly outbred isolated cases of cousin marriage are not particularly deleterious, but in many cultures systemic inbreeding results in tunneling and narrowing of lineages into discrete effective population pools where stochastic effects start to loom large. In plain English, the number of unique ancestors in inbred clans starts drop in relation to what one would predict in a panmictic context. Deleterious recessives masked in the ancestors are then…
razib | August 1, 2006There has been talk about rock star scientists and what not on Science Blogs. Rock stars? Isn't that so baby boomer? So let me rephrase it: who is the thug geneticist? I'll nominate Bruce Lahn, an evolutionary genomicist at the University of Chicago. According to Chicago Lahn is down with "Get Rich or Die Tryin'," by 50 Cent, so we know he already likes it hard-core hip hop style. Also, points for the fact that Lahn is an intellectual mugger who will leave you feeling violated.
razib | August 1, 2006RPM points me to a post at Salamander Candy which discusses the usefulness of neutral markers in conservation genetics. Obviously this complements my recent posts about introgression, and in fact, my last entry was a comment on a conservation genetic paper. Here is the important point from Salamander Candy:
The problem is, a growing body of evidence suggests that patterns of variation and divergence in adaptive traits are not well reflected by neutral markers...In the hypothetical species mentioned above, a small amount of gene flow between east and west would be enough to swap small…
razib | July 31, 2006Apropos of our discussion of evolution and dogs, and introgression, here is a new paper I stumbled upon in Molecular Ecology, Detecting introgressive hybridization between free-ranging domestic dogs and wild wolves (Canis lupus) by admixture linkage disequilibrium analysis. Linkage disequilibrium is basically the non-random association of alleles across loci. For example, imagine that you have alleles A1 and A2 at locus A, and B1 and B2 at locus B. Imagine that these two locii are on separate chromosomes (just to make it clearer, though they don't have to be). In a randomly mating…
razib | July 31, 2006Don't have time to read all the Science Blogs? Don't worry, Bora's put together a literal tapas of selections, part I, part II, part III and part IV.
razib | July 31, 2006Alex points me to this Rebecca Goldstein op-ed in The New York Times marking the excommunication of Baruch Spinoza. I am actually reading Goldstein's biography of Spinoza, Betraying Spinoza: The Renegade Jew Who Gave Us Modernity, and just finished Matthew Stewart's The Courtier and the Heretic: Leibniz, Spinoza, and the Fate of God in the Modern World. Most of you probably know the name Spinoza from Einstein's assertion that he "believe in Spinoza's God," the pantheistic entity which suffused existence itself.
Update: James H. has more at The Island of Doubt.
Stewart, and Goldstein from…
razib | July 27, 2006I suspect the basic general process of introgression is clear to most of you, though I will get back to it soon. But here are some papers with candidate genes (click "related" for more references):
RRM2P4, dystrophin, xp21.1 and 17q21.31. Also, I should add in the amusing evidence that archaics and moderns had sexual intercourse (amusing, but scientific nonetheless). Finally, a more theoretical paper that just came out.
There are other possibilities, like MC1R, but that could also be frequency dependent selection. More to come soon, I promise....
razib | July 27, 2006Seed has a piece on the discoveries relating to menopause and its importance to the "Grandmother Hypothesis." Unlike male decline in fertility menopause is a specific and deliberate sequence of proactive processes by the female body to shut down reproductive capacity. Something like this is almost certainly functionally significant, and anthropological work which seems to show cross-cultural evidence of lower infant mortality in the presence of a maternal grandmother in the household is another important avenue in the overall program.
razib | July 26, 2006Here is the definition from Wiki:
Introgression is a term used in genetics, particularly plant genetics, to describe the movement of a gene from one species into the gene pool of another by backcrossing an interspecific hybrid with one of its parents. Introgression of a transgene from a transgenic plant to a wild relative as the result of a successful hybridization is an example.
Illustration. You have a Eastern European mouse and a West European mouse. On the boundary between the two species West European females mate with East European males, and the F1 hybrid females mate only with East…
razib | July 26, 2006Since Jonah posted on the French IQ study profiled in The New York Times Magazine, I thought I'd point to an analysis of the data by a co-thug over at GNXP Classic. Warning, if 2 X 2 ANOVA bores you, prepare to be bored. Otherwise, enjoy.
Update: Alex has more analysis.
razib | July 26, 2006Update: It maybe that "idiot commenter" speaks English as a second language , and so was not expressing his skepticism with sufficient nuance for my taste. That being said, this post stands as a warning to those who would waste my time.
-God Bless, Razib
This commenter starts out by admitting that he didn't follow all my reasoning in my post on Neandertal admixture, but proceeds to take a patronizing tone. What bullshit. I know that some of my posts make recourse to terms which are a bit technical, in fact, terms which I myself didn't grasp well until a few years ago, and whose conceptual…