genetics
razib | April 22, 2006John Wilkins has a post on race where he expresses skepticism about its biological reality. He comment was in response to a post on my other blog (by another individual), but I'll stand by it.
I've talked abut race in the past, and I'm not into the topic at this point since it is going over old ground, but a few quick responses....
Re: Lewontin's point about 85% within group vs. 15% between group variance, that is true, at one locus, but it ignores the correlation structure across loci. This is elucidated by mathematical geneticist Anthony Edwards in his paper from a few years back (PDF…
evolgen | April 21, 2006Pharyngula has a good summary of the new Sean Carroll Drosophila wing dot paper. Eventually Sean's gonna try to mess around with a hawaiin species and blow the roof off this mother.
pharyngula | April 21, 2006a–c, The wing spots on male flies of the Drosophila genus. Drosophila tristis (a) and D. elegans (b) have wing spots that have arisen during convergent evolution. Drosophila gunungcola (c) instead evolved from a spotted ancestor. d, Males wave their wings to display the spots during elaborate courtship dances.
It's all about style. When you're out and about looking for mates, what tends to draw the eye first are general signals—health and vigor, symmetry, absence of blemishes or injuries, that sort of thing—but then we also look for that special something, that je ne sais quoi, that dash of…
razib | April 20, 2006Check out this cool paper in PLOS Genetics:
In this first application of the approximate Bayesian computation approach using the serial coalescent, we demonstrated the estimation of historical demographic parameters from ancient DNA. We estimated the timing and severity of a population bottleneck in an endemic subterranean rodent, Ctenomys sociabilis, over the last 10,000 y from two cave sites in northern Patagonia, Argentina....We found a decrease from a female effective population size of 95,231 to less than 300 females at 2,890 y before present: a 99.7% decline. Our study demonstrates the…
pharyngula | April 19, 2006
Here's what seems to be a relatively simple problem in evolution. Within the Drosophila genus (and in diverse insects in general), species have evolved patterned spots on their wings, which seem to be important in species-specific courtship. Gompel et al. have been exploring in depth one particular problem, illustrated below: how did a spot-free ancestral fly species acquire that distinctive dark patch near the front tip of the wing in Drosophila biarmipes? Their answer involves dissecting the molecular regulators of pattern in the fly wing, doing comparative sequence analyses and…
razib | April 19, 2006Richard Dawkins pioneered the popularization of the "selfish gene" concept in the book of the same name in the 1970s, and yet it is clear that most people haven't really internalized this idea. Otherwise, how to explain the success of books like The Journey of Man and The Seven Daughters of Eve which explicitly conflate population history and gene history to the point where one would assume a 1:1 covariance.
In the post below I pointed to a paper, Local extinction and recolonization, species effective population size, and modern human origins, which shows how more non-trivially simple models…
razib | April 19, 2006I've been a bit anal about genetic drift over the past few days. The reason is simple, replace "random genetic drift" with "sampling error", and note how ridiculous some of the things scientists will say to journalists when they come a callin' sound all of a sudden. "Hm...no, I haven't done research in this area, but it seems like sampling error could generate that sort of pattern." "Well, it could be sampling error, they can't prove it isn't." I'm not saying that random genetic drift isn't a good null hypothesis, I'm just saying that it is a deux ex machina that sounds good when you can't…
razib | April 18, 2006The spawn of TomKat lives! Abiola Lapite speculated that Cruise had holoprosencephaly, which would result in miscarriages in his partners. I emailed Lapite and his response was "And how exactly do you know it's his?" Good point. The Superficial has more of course.
razib | April 17, 2006Interesting profile of Roman Catholic evolutionary biologist Francisco Ayala. As an aside they note:
In conducting the studies he had suggested, Ayala also made the unexpected discovery that the parasite P. falciparum can reproduce not just sexually, but clonally as well: it can fuse male and female gametes - sexual reproduction - or transmit all of its genes as a single unit, the cloning that was an unexpected phenomenon.
Ayala's discovery has helped reveal that malaria, which now kills up to 2.7 million people per year - mostly African children - became common only within the last 5,000…
razib | April 17, 2006Just a quick review about some issues that I assumed implicitly in my post where I took issue with genetic drift as a force for population variation. It isn't like genetic drift can't result in variation...but the researcher seemed to be pointing to founder effect which would homogenize alternative populations and "fix" them into alternative states. For founder effect to really work you need to reduce the effective population size and squeeze genetic polymorphism out of the gene pool. Consider the equation for decline in heterozygosity1:
Ht = (1 - 1/(2N))tH0
Where H0 is the intial…
razib | April 17, 2006Below the fold is an image of a fine specimen of fitness being signalled by aesthetic characters....
Update: Behold, the oogly-cat:
razib | April 17, 2006I read the paper that Afarensis pointed me to, Cranial morphology of early Americans from Lagoa Santa, Brazil: Implications for the settlement of the New World. I found it somewhat persuasive. The authors basically posit two primary waves of humans that settled the New World, a "generalized" form that entered before 10,000 years BP, and a specialized "Mongoloid" form that we know as Native Americans who arrived around 10,000 years ago. As John Hawks notes, this model has been proposed for other regions of the world. In regards to "specialized" human populations, The Real Eve Stephen…
razib | April 16, 2006Afarensis has a long post worth reading about new discoveries relating to the peopling of the Americans. This is a controversial topic, Moira Breen has been covering this issue for several years now in relation to the famous Kennewick Man. But, this caught my eye:
Still, not all scientists are convinced that the variations found in the skulls are proof of multiple migrations to the Americas.
"There is a huge amount of variation among the first Americans, more than you see among any other population outside of the Pacific," said Joseph Powell, an anthropologist at the University of New…
razib | April 16, 2006Below I mentioned the doyen of living population geneticists, James Crow, yeah, Jim Crow. Collaborater with Motoo Kimura of Neutral Theory fame, Crow is still an active member of the biological community. Recently he reviewed Genes in Conflict : The Biology of Selfish Genetic Elements by Bob Trivers & Austin Burt in Nature. He begins:
In the early 1970s, Robert Trivers published six articles on the evolution of social behaviour. They were ignored by most social scientists, who were reluctant to consider natural selection as a cause of human behavioural traits, and they were bitterly…
evolgen | April 15, 2006From the London Times:
In a series of Good Friday meditations that he will lead in Rome, the Pope will say that society is in the grip of a kind of "anti-Genesis" described as "a diabolical pride aimed at eliminating the family". He will pray for society to be cleansed of the "filth" that surrounds it and be restored to purity, freed from "decadent narcissism".
Yo, bro, if you want to free society from "decadent narcissism" you could start by moving out of that huge mansion. I've been there. The place is awesome, but the dresses, funny hats, and some sort of special connection to God sure…
razib | April 12, 2006According to The New York Times Seeking Ancestry in DNA Ties Uncovered by Tests is the most emailed article today. As I've stated before, I believe this area of science & technology is driven by psychology. The same drive which has led men and women to enter into the time consuming hobby of genealogy for hundreds of years. Below, NuSapiens offers the opinion that the new technology will undermine the current orthodoxies and mentalities in regards to race. Unfortunately, I don't believe that anymore...I just think people are too driven by their intuitive pattern matching &…
razib | April 11, 2006There's a terrifying article in The New York Times titled Seeking Ancestry in DNA Ties Uncovered by Tests. Here is a sample:
Alan Moldawer's adopted twins, Matt and Andrew, had always thought of themselves as white. But when it came time for them to apply to college last year, Mr. Moldawer thought it might be worth investigating the origins of their slightly tan-tinted skin, with a new DNA kit that he had heard could determine an individual's genetic ancestry.
The results, designating the boys 9 percent Native American and 11 percent northern African, arrived too late for the admissions…
razib | April 11, 2006I just skimmed through Human Biological Variation today. It was somewhat disappointing, the exploration of topics was often too superficial and I really didn't need a review of what mitosis, meiosis and Hardy-Weinberg Equilibrium were. They do collate some interesting data in the latter portion of the book, but the only one I'd like to pass on is about blood groups. This is one genetic trait which most of us happen to know about our own status in regards to, I'm an A, my father is a B and my mother is an A. But we are often under the impression that this is capricious, and the variation in…
razib | April 10, 2006Gary Marcus, author of The Birth of the Mind, has a pithy piece in The New York Times, From Squeak to Syntax: Language's Incremental Evolution, which sketches out the refinements that the new science of genomics is adding to our understanding of the origins of language. In fact, one could argue that it isn't adding, it is actually building the initial foundations. Many of you probably also know that the Linguistic Society of Paris banned the discussion of the origin of language in 1866 because it seemed to be simultaneous attractive and intractable. Though Noam Chomsky was one of the major…
razib | April 9, 2006No, not really, but perhaps a British newspaper will pick up this meme and I'll be responsible for a butt-load of misinformation. You gotta get fame somehow! Anyway...
Cohort effects in a genetically determined trait: eye colour among US whites:
The prevalence of blue eye colour among non-Hispanic whites in NHANES-III was 57.4% (95% CI: 50.1-64.7) for individuals born between 1899 and 1905 compared to 33.8%...for those born between 1936 and 1951. No association was found between survival and eye colour, nor was a cohort effect evident for primary ancestry. However, proportions reporting…