I have previously posted on the subject of social mobility (for example here), so I thought I would report on an interesting new study by economists at the London School of Economics. A pdf copy is available here (NB: as this study has been in the news, the server may be temporarily overloaded. If so, try again later.)

Briefly, the study compares evidence on social mobility from eight countries: the UK, the US, Canada, Germany, Denmark, Norway, Sweden and Finland. Key findings are that:

– social mobility is highest in the Scandinavian countries and lowest in the US, with the UK second lowest and Germany somewhere in between

– social mobility in the UK (but not elsewhere) has fallen since the cohorts born in the late 1950s. The authors attribute this to the interaction of parental income and the education system: as access to higher education has increased, children from better-off families have taken more advantage of the new opportunities. In comments to the press, one of the authors has also said that the abolition of the eleven-plus system (selective secondary education based on ability) has hindered the prospects of bright children from poorer families.

I won’t analyse this in detail, but I don’t find anything in the report hugely surprising. However, I would put more emphasis than the authors on the high levels of mobility in all the countries studied. The correlation between parental income and child’s income is in all cases quite weak, and the majority of children are in a different social/income class from their parents. The authors somewhat obscure this basic fact by comparing the distribution with a hypothetical model of ‘perfect mobility’, in which the correlation between parents and children would be zero. Since this would imply that parents contribute nothing, by either nature or nurture, to their children’s life chances, it should be dismissed as a fantasy.

The relatively low mobility in the US may raise some eyebrows, but the idea that social mobility in the US is higher than elsewhere has always been something of a myth. The authors also point out that in the US social mobility is affected by race, as it is lower among blacks than among whites.

The educational implications of the UK findings will no doubt cause some debate. There is growing recognition, even among the chattering classes, that education for the bottom 20 percent or so of the socio-economic scale is a disaster area.

It would be interesting to know more about the reasons for high social mobility in the Scandinavian countries. The thought just crossed my mind that social mobility may be positively related to the size of the public sector, since the public sector, whatever else may be said about it, does tend to recruit and promote people on the basis of IQ and academic qualifications, rather than family connections. Social mobility may be low in countries where much of the economy is in family businesses. But this hypothesis would need a lot of investigation.

Posted by David B at 03:04 AM

EurekAlert! summarizes a paper by Rushton and Jensen to appear in the June issue of Psychology, Public Policy and Law in ten handy points:

The Worldwide Pattern of IQ Scores. Race Differences Most Pronounced on Tests of (g).The Gene-Environment Architecture of IQ.Brain Size Differences.Trans-Racial Adoption Studies.Racial Admixture Studies.IQ Scores of Blacks and Whites Regress toward the mean.Race Differences in Other “Life-History” Traits.Race Differences and the Out-of-Africa theory of Human Origins.Do Culture-Only Theories Explain the Data? Update from Razib: Whole thing here (PDF).

Update from Alex: From Marginal Revolution via eric, comes a great supplimental reading in April 2005’s Journal of Law and Economics entitled Labor Market Discrimination and Racial Differences in Premarket Factors (free *.pdf here). Posted by jemima at 08:17 PM

Genetic variation increases during biological invasion by a Cuban lizard (Nature):

A genetic paradox exists in invasion biology: how do introduced populations, whose genetic variation has probably been depleted by population bottlenecks, persist and adapt to new conditions…Genetic analyses indicate that at least eight introductions have occurred in Florida from across this lizard’s native range, blending genetic variation from different geographic source populations and producing populations that contain substantially more, not less, genetic variation than native populations. Moreover, recently introduced brown anole populations around the world originate from Florida, and some have maintained these elevated levels of genetic variation. Here we show that one key to invasion success may be the occurrence of multiple introductions that transform among-population variation in native ranges to within-population variation in introduced areas.

Basically, you have a process where various demes have fixed (or moved toward that direction) on various loci. The initially low level of polymorphism is further depleted by the enormous sampling error that often occurs during selection for a founding event. But, these originally isolated genetic populations came into contact and mixed, producing genetically varied descendent populations.

The moral is that there are many ways that nature reduces genetic diversity, from random genetic drift to persistent directional selection, but migration is one way that intrapopulational diversity can increase.

Full paper (PDF).

Addendum: change in allelic frequency = proportion of migrants in parental generation of given population * (frequency of allele in parental population of given population for non-migrants – frequency of allele in parental population of given population for migrants), or change Δp = m * (pnatives at t – pmigrants at t).

Related: Fisher’s “Fundamental Theorem of Natural Selection”: The rate of increase in fitness of any organism at any time is equal to its genetic variance in fitness at that time. In short, the rate of evolutionary change is proportional to the genotypic variation that selection has to work with. Here is the related math.

Posted by razib at 09:37 AM

Coming soon: drugs to match your DNA.

SCOTTISH doctors are building a unique gene database that will match medicines to individual patients, boosting the chances of effective treatment while reducing side-effects.

Posted by razib at 04:17 PM

Method shows how precisely gene expression signals are copied in DNA replication

“A group of University of Washington researchers has devised a method that combines DNA sampling and mathematical modeling to find out how accurately methylation patterns are copied during DNA replication. That could pave the way for understanding the role methylation plays in normal gene expression and how it factors in the development of human disease.”

…
“Methylation typically passes from genes in a DNA strand to the same genes in a daughter strand created during DNA replication. The new technique allows researchers to examine how faithfully this “maintenance” methylation is carried out across generations and how consistently it occurs on the same gene sequence, said Brooks Miner, a UW research scientist in biology and a co-author of the paper.

But DNA molecules also can undergo what is called “de novo,” or new, methylation in which a methyl group shows up on a DNA strand at a place where it did not appear before. That could change how that particular gene sequence is expressed.”
…
“In the past, researchers could look at only one strand of DNA at a time and so could not conduct a side-by-side comparison of where methylation was occurring. An earlier paper from the same research group, led by Charles Laird, a UW biology professor, introduced a molecular method to look at both DNA strands together and observe methylation differences between them.”

Posted by fly at 09:03 AM

Brain imaging study explains Williams syndrome language gifts:

“Findings: A team of neuroscientists led by UCLA researchers used a novel magnetic resonance imaging (MRI) technique to create the first detailed images showing how Williams syndrome affects the cerebral cortex. The study finds sharply defined cortical thickening and complexity in the area of the brain important to language.

Impact: The isolated, thickened cortical region in language areas is remarkable because patients with Williams syndrome show marked strengths in language and related abilities. The ability to map these abnormalities in living patients demonstrates how genes control development of the human cortex, and also aids clinical prognosis and understanding of the syndrome’s underlying genetic trigger.

Background: Williams Syndrome is a genetic disorder characterized by heart defects, abnormalities in the outer layer of the brain, or cerebral cortex, and mild to moderate mental retardation. In addition, people with Williams syndrome often demonstrate high proficiency in language skills, social drive and musical ability. The syndrome affects 1 in 20,000 individuals.”

Posted by fly at 08:30 AM

Racist nazi ice cream causes uproar in Sweden! Read all about it! Pictures inside!

The Nazi ice cream from hell:

And the money quote:

“Soon the Ice cream giant was slammed for “racist” ads as the Center Against Racism issued a press release denouncing the new ice-cream. “*

* This is a tax-payer funded organization.

More shocking pictures inside!

Swedish Ice Cream giant GB has now yielded, and has offered up an alternative, non-offensive ice-cream:

*”kokoskon” = “cocotop”

…meanwhile, critics of the Center against racism have fallen silent, as new shocking evidence is discovered in German archives:

PS.

There were no Sweden-related posts on the front page – just had to be rectified.

DS

Posted by dobeln at 11:30 PM

There has been some talk about the new Pope and evolutionary theory. I certainly haven’t read In the Beginning…: A Catholic Understanding of the Story of Creation and the Fall, a book that is a collection of five of Ratzinger’s homilies from the early 1980s, but the online references seem to suggest plain vanilla theistic evolutionism, not the fleshy hopeful monster that is Intelligent Design (you can use Amazon’s “search inside” feature to read much of the text. There are some portions where Ratzinger’s usage of terms, or, more properly the translation from German, resembles typical Intelligent Design cant. But, reading earlier portions of the homily in question makes me skeptical that he was speaking in a specific and precise fashion as opposed to a general assertion of the salience of Design in a Thomistic fashion. And of course, the homilies were composed over a decade before ID emerged). Nevertheless, this document, titled Human Persons Created in the Image of God has some material about evolution in it, and it states:

…The present text was approved in forma specifica, by the written ballots of the International Theological Commission. It was then submitted to Joseph Cardinal Ratzinger, the President of the Commission, who has give his permission for its publication.

Below is an interesting excision, but, I suggest you click through and skip down to paragraph 62 (they are numbered) and read the whole section “Science and the stewardship of knowledge.” I don’t agree with Benedict XVI on many things, but, I am also not one who dreads the possibility that somewhere out there dwell monstrous beings who not only disagree with me on important issues, but holds opinions I find highly objectionable. To be offended is to be human, to respond is only natural.

63. According to the widely accepted scientific account, the universe erupted 15 billion years ago in an explosion called the “Big Bang” and has been expanding and cooling ever since. Later there gradually emerged the conditions necessary for the formation of atoms, still later the condensation of galaxies and stars, and about 10 billion years later the formation of planets. In our own solar system and on earth (formed about 4.5 billion years ago), the conditions have been favorable to the emergence of life. While there is little consensus among scientists about how the origin of this first microscopic life is to be explained, there is general agreement among them that the first organism dwelt on this planet about 3.5-4 billion years ago. Since it has been demonstrated that all living organisms on earth are genetically related, it is virtually certain that all living organisms have descended from this first organism. Converging evidence from many studies in the physical and biological sciences furnishes mounting support for some theory of evolution to account for the development and diversification of life on earth, while controversy continues over the pace and mechanisms of evolution. While the story of human origins is complex and subject to revision, physical anthropology and molecular biology combine to make a convincing case for the origin of the human species in Africa about 150,000 years ago in a humanoid population of common genetic lineage. However it is to be explained, the decisive factor in human origins was a continually increasing brain size, culminating in that of homo sapiens. With the development of the human brain, the nature and rate of evolution were permanently altered: with the introduction of the uniquely human factors of consciousness, intentionality, freedom and creativity, biological evolution was recast as social and cultural evolution.

…

70. With respect to the immediate creation of the human soul, Catholic theology affirms that particular actions of God bring about effects that transcend the capacity of created causes acting according to their natures. The appeal to divine causality to account for genuinely causal as distinct from merely explanatory gaps does not insert divine agency to fill in the “gaps” in human scientific understanding (thus giving rise to the so-called “God of the gaps”). The structures of the world can be seen as open to non-disruptive divine action in directly causing events in the world. Catholic theology affirms that that the emergence of the first members of the human species (whether as individuals or in populations) represents an event that is not susceptible of a purely natural explanation and which can appropriately be attributed to divine intervention. Acting indirectly through causal chains operating from the beginning of cosmic history, God prepared the way for what Pope John Paul II has called “an ontological leap…the moment of transition to the spiritual.” While science can study these causal chains, it falls to theology to locate this account of the special creation of the human soul within the overarching plan of the triune God to share the communion of trinitarian life with human persons who are created out of nothing in the image and likeness of God, and who, in his name and according to his plan, exercise a creative stewardship and sovereignty over the physical universe.

Stripping away the theological verbiage much of the above commentary about human evolutionary origins in particular almost resembles a “Great Leap Forward” narrative.

Posted by razib at 08:52 PM

Method devised for whole-population DNA analysis. Seems more like a press release by the founder of a new biotech company than anything else, but there is more at The Wellcome Trust’s website. The projected company seems like it is looking to capitalize on the window of opportunity before the rise of truly personal genomics and leverage populational level differences data toward medical applications. Nevertheless, apropos of some discussions on this site, this method might have more purely intellectual relevance.

Posted by razib at 03:37 AM

In the comment board Theresa asserted: “Another side note, lots of ethnic Norwegians have dark hair and dark eyes — the blonde, blue-eyed folks are mainly in the inner valleys — and over there in Sweden.” I don’t know if this is true, but, it did make me wonder.

My post Why evolution doesn’t make sense ruminated over the difficulties that lay people have when they think about evolution. The macroevolutionary realities tend to overshadow the more operationally relevant microevolutionary details.

Let us assume that Norwegians of the inland valleys do tend to be blonder than coastal Norwegians. Why could this be?

Here are some quick answers people might come up with.

Migration-clinal admixture: In her comment Theresa alluded to the fact that Swedes tend to be blonde. When physical anthropologists had a great concern about such topics a common data point brought up was that southern Sweden represented the modal frequency of the “blue eyed blonded” “Nordic” type. In fact, some texts asserted that only in southern Sweden did the intersection of blue eyes and blonde hair characterize the majority of the population. From this it is common sense to assume that blondism decreases as a function of distance from southern Sweden.

Modern paternal and maternal DNA markers suggest that it is possible that northern Europe was “repopulated” after the Last Glacial Maximimum by disparate populations that have been driven south into “refuges.” Iberia, the eastern European borderlands and the Balkans are the primary candidates for the nodes from which the demographic expansion repopulated Europe. Luigi Cavalli-Sforza’s magmum opus The History and Geography of Genes prefigured the findings of the later geneticists as he transformed various principal components of variation in his data sets into rich maps that illustrated clinal transitions issuing out of the southeast, southwest and east.

The details of this model are not relevant, rather, I would like to point out physical anthropologists have observed an increase in the frequency of dark hair as one moves to the west in the British Isles, the Welsh being darker than the English and the western Irish being less blonde than the eastern Irish. All this is to flesh out the possibilities that admixture and various migrational movements (blondes from the east intermarrying with dark haired people migrating up from Iberia) might account for the local phenomenon of inland folk being blonder in Norway.

Selection: Another hypothesis is that microevolutionary selective pressures have resulted in the differences between inlanders and costal dwellers. If one opens the can of worms that is social and sexual selection the possibilities are endless, rather, I will point to the more prosaic option: coastal dwellers did not need to synthesize as much Vitamin D because they could acquire that nutrient through fish oil. Therefore, the blondeness of the highlanders is a correlated response to the selection for fair skin, which facilitates endogenous synthesis of Viatmin D.

But these aren’t the only options. #1 is something that the typical person might offer without any prompting or recourse to research. The exact details of #2 are more difficult to intuit from common sense, while the various possible epicycles that sexual and social selection imply are not even on the table in conventional disource.

And yet, as the title suggests, there is another option: Random Genetic Drift might be the cause of the higher frequency blondeness among the highland population. And this “Random Genetic Drift” might not be happenstance, that is, the highland populations simply random walked into a higher frequency of the blonde phenotype, rather, it might be an inevitable consequence of particular tendencies toward population substructure.

The thought is triggered by my reading of some of Cavalli-Sforza’s original work in Italy. He foud that people who lived in the mountainous regions and away from the coasts had far more constricted marital networks. They were more inbred because their operational “deme,” the rough & ready breeding population, was far smaller, and not only did they share many coancestors but they were subject to greater forces of drift. In fact, the correlation between topography and the average distance of birth between the spouses was larger striking. Lowland people were aided by good roads, gentle grades as well as the supplement of water transportation. Though the lowlanders (at this time) might not have been economically that much more advanced than their highland neighbors, they were part of a much more tightly integrated wider social and populational network. The marital connections and gene flow between the lowland villages was far greater than what one found among the highland villages.

Which brings us back to Norway. Qualitatively the model can be described as thus: lowland Norway is a large deme where Random Genetic Drift has had less power because of the high effective population size. In contrast, the highland demes are rather small, and so each has been buffeted by sampling error, Random Genetic Drift, to a far greater extent than the lowlanders. A crucial point is that the swings should cancel out so that the frequencies of alleles might not differ very much between the lowland deme and “the highlands,” but because of the high degree of population substructure there are many populations where alternative alleles have been fixed. This is where blondeness comes it: it is traditionally characterized as a phenotype that is expressed when the alleles are present as homozygous. So, while in the lowland deme 50% of the alleles might be for “blondeness,” only about 1/4 of the population is blonde because only 1/4 is homozygous for blonde alleles. In contrast, though the highlanders as an aggregate might be characterized by the same allelic frequencies as the lowerlands, say a 50-50 split between “blonde” and “brunette” alleles, the frequency of heterozygotes where the blonde allele is masked by a brunette allele is far lower, so the number of blondes is far higher because of the rise in homozygosity due to Random Genetic Drift.

I don’t know if this story is true, I don’t know if the highlanders are blonder or more inbred than the lowlanders. Rather, I simply wanted to offer it as an explication of the power of simple genetic logic.

Addendum: My source for the clarification is Genetics of Populations by Philip Hedrick. I have made a few minor changes because of the limitations of HTML.

Kimur and Ohta’s diffusion aproximation for a continous-time model for the mean time until fixation of allele A2 (in this case “blondeness”) with an initial frequency q:

(1) – T(q) = – [4N(1-q) ln(1-q)]/q

As you can see, time until fixation is a function of population size, N, and the initial frequency. Let us assume that All-Father Odin created 200,000 Norwegians in Valhalla. Their frequency of alleles was A1 = 0.5 and A2 = 0.5. He divided them into two groups, the “lowland population” (L) and the “highland population” (H) of equal numbers, 100,000 each. Then, he settled the L group on the coasts. These villages and towns and farmsteads were connected by coastal roads and long-boats. They were functionally one population, one deme. In contrast, the H population was diffused amongst 100 valleys in equal portions, so you have H1…H100, each with an effective population of 1,000.1

Loki, trickster than he is, decides to put up walls between the L deme and all the H demes, as well as partitions between the H demes themselves. In other words, no migration. Also, Loki get’s everyone drunk so that everyone mates with whoever they bump into at the local da
nce in a random fashion, so, no selection. Frey, feeling bad for them due to his Vanir soft heart decrees that they shall all birth perfect children, so, no mutation.

For population L, equation 1 suggests that the “mean time to fixation” for either allele will be about 280,000 generations. This doesn’t mean it will necessarily take 280,000 generations, and offers no clue as to which one will really fix, but if you were All-Father Odin and turned time back and allowed the Norns to work their dice 280,000 would be the average time of fixation among the repeated iterations.

For the various H populations equation 1 suggests that fixation is going to happen on average in each population in about 2,800 generations. This makes sense, the N was 1/100th the size of L for each of them.

The probability of fixation for each allele is their initial frequency. In this case both have an equal shot, but, the substructure implies something special: after a long enough period L might fix, but “H” will likely not fix for a particular allele (it is not really one population aside from the ecological commonality), rather, each of the various H demes will fix, and the expected ratio A1 homozygotic demes to A2 homozygotic demes ratio should be 1:1.

Update: On second thought, I want to reiterate that I present the above argument for illustration’s purpose primarily. If I was serious I suppose I would look to some sort of island model, but my interest in highlighting the topic was mostly to spur readers to explore the simple but often counter-intuitive concepts and algebra of population genetics. A high degree of fluency with the material requires good working knowledge of differential equations and linear algebra, but the basics are pretty accessible if you have high school algebra.

1 – Gods have perfect sampling sight, even with one eye. There isn’t any “founder effect” at work here.

Posted by razib at 06:27 PM