Two PNAS papers today that caught my eye, going to read for later, Distinct genomic signatures of adaptation in pre- and postnatal environments during human evolution and Defining genetic interaction. Both Open Access.

Labels: Genetics

A story about Alice Fraasa the Snorg Tees girl. I've been bombarded on The New York Times website with the ads all week and I clicked. I assume that it has ads all the time, but hell if I could tell you what they were about, I don't notice them. Until this week. Other people must have clicked too, the Snorg Tees link was down. Assume this is a new ad buy and their network engineers weren't ready for the increase in traffic....

Empire: How Spain Became a World Power, 1492-1763 is an excellent narrative history which focuses on the period of time when Spanish history was a substantial subset of world history. The author, Henry Kamen, is a British historian who happens to be a resident of Barcelona, and he's gotten into trouble with Spanish nationalists for not framing the facts in a manner befitting Castilian triumphalism. All for the good I would think. In any case, Kamen does a good job balancing the standard kings & battles narration with thick social history. I checked out the book for two reasons. First, I was interested in the treatment given to the impact of disease in its relation to the New World, and secondarily, a better understanding of the role of the Hapsburg dynasty in early modern European history (I'm working through another book focusing on the Austrian Hapsburgs). Though the author was more interested in the social and economic parameters which drove the Spanish conquest of the New World, he really couldn't dodge the critical necessary precondition of disease, so I found out what I needed to know. Imagine that the sepoys who fought for the East India Company and the maharajas who aligned with the British were extinct a generation or two after the aid that they rendered the new sahibs. That's a pretty good analogy. On the second issue, there was a lot of detail which was illuminating; who knew that Phillip the II was a connoisseur of Dutch culture? I didn't (though I did know that Charles V was a Netherlander, I suspect that my Anglo-Saxon cultural background has inculcated me thoroughly with the Black Legend). But there some other more surprising points which I hadn't thought of.

First, I did know of one dynamic which plays a large role in explaining various events in Spanish history: during this whole period the Spanish Empire, and even the core kingdom of Spain, was actually a dynastic union which was relatively unintegrated politically. In fact, the Carlist Wars of the 19th centuries were fought over in part by the regions to preserve their customary laws and traditions against the centralizing tendency of the crown (or one lineage of it), which was attempting to create a modern nation-state. In an ironic but unsurprising twist, the same regions, such as the Basque provinces and Catalonia, which had served as centers of traditionalist-reactionary factions switched to supporting Leftish movements when those political configurations supported their autonomy from the centralizing pressures of Madrid. So in the 19th century the regions of Spain supported reaction and tradition because that reaction and tradition overlapped with their independence. In the 20th century conservatives had become reconciled with the nation-state and so it was to the Left that these regions looked to to support their aspirations for freedom from Castilian imperialism. But I had not been aware of the extent to which regions such as Aragon, which was a separate kingdom from Castile under the same monarchy, were definitively independent. Not only would the assemblies of Aragon refuse to be taxed to support wars on behalf of the Spanish Empire (e.g., the attempt to suppress rebellion in the Netherlands), but they also might refuse to send troops! This was not an isolated incident, it seems that the New World was Castile's responsibility, while Aragon looked towards its own possessions in Italy. Speaking of which, Kamen points to the fact that these Italian possessions, in particular Genoa, provided much of the capital and financial talent which kept the Empire afloat. Christopher Columbus was not the only Genoese in the service of the Spanish crown, the trade with the New World based out of Seville was backed in large part by non-Castilian capital, whether it be Italian, Portuguese or German.

I only emphasize the international aspect to the Spanish Empire (which was Kamen's sin in the eyes of Spanish historians who wanted to highlight Castile's overwhelming agency in all events) because the text is also littered with references to a particular parochialism of Castilian culture and society which is all too familiar. Kamen notes that, for example, in the 16th century Castilian literature was relatively popular in translation in other parts of Europe. But the Castilians rarely translated works in other languages into the their own! Additionally, even Castilian works were usually printed abroad because of the relative shoddiness of local artisans and technology; often in the possessions which later became Belgium or in Italy. Finally, Kamen observes that the Spanish foreign service had difficulties because of the lack of polyglots in Castile; generally diplomats would make recourse to translators, or, they would recruit from Italy, Flanders or Wallonia, because many in those regions would know Castilian as well as their own native tongue and possibly other languages. There are numerous other examples given the text. Assuming this is correct, it reminds me a great deal of aspects of the Ottoman or Chinese interaction with the West when these societies were in relative decline, down to the lack of interest in foreign arts & literature as well as the need for middlemen to translate because of linguistic ignorance. Of course, a one-dimensional picture of these societies is going to be incorrect, there were attempts to modernize from within and influences from without. But a strong overall sense pervades that these cultures were inwards looking by conscious preference and their elites were very satisfied with their station in the world and saw no need to measure themselves against outsiders.

One could chalk this up to Muslim influence in Spain. But resemblances to the last century of the Chinese Empire suggest to me that this is a repeated pattern in many societies which have reached an equilibrium which can be broken only by powerful exogenous shocks. One could imagine for example something very similar to what happened to the Ottomans and Ching (Manchus) if a Slavophile faction had succeeded in keeping the Russian aristocracy insulated from Western European influences (as one was, one could make the case that something like this did happen because of the inability to shift from the outmoded absolutism which the Tsars perpetuated). I don't have a real answer to what was going on in Spain, but I had to comment on the correspondences with the trajectory of the Ottoman Empire at the other end of the Mediterranean. After a vigorous expansion under a warrior caste both these polities seemed to have just decided to take a few centuries long nap, spelled by occasional attempts to modernize and catch-up, but only in terms of specific ends as opposed to general techniques.

Labels: History

Evaluation of Genetic Variation Contributing to Differences in Gene Expression between Populations (Open Access):

Gene expression is a complex quantitative trait partially regulated by genetic variation in DNA sequence. Population differences in gene expression could contribute to some of the observed differences in susceptibility to common diseases and response to drug treatments. We characterized gene expression in the full set of HapMap lymphoblastoid cell lines derived from individuals of European and African ancestry for 9156 transcript clusters...Gene expression was found to differ significantly between these samples for 383 transcript clusters. Biological processes including ribosome biogenesis and antimicrobial humoral response were found to be enriched in these differential genes, suggesting their possible roles in contributing to the population differences at a higher level than that of mRNA expression and in response to environmental information. Genome-wide association studies for local or distant genetic variants that correlate with the differentially expressed genes enabled identification of significant associations with one or more single-nucleotide polymorphisms (SNPs), consistent with the hypothesis that genetic factors and not simply population identity or other characteristics (age of cell lines, length of culture, etc.) contribute to differences in gene expression in these samples. Our results provide a comprehensive view of the genes differentially expressed between populations and the enriched biological processes involved in these genes. We also provide an evaluation of the contributions of genetic variation and nongenetic factors to the population differences in gene expression.

ScienceDaily has the digest.

Labels: human biodiversity

The Audacious Epigone crunches the Pew Religion Survey and comes up with some more insights....

Labels: Religion

Pathogen prevalence predicts human cross-cultural variability in individualism/collectivism (Open Access):

...We suggest that specific behavioural manifestations of collectivism (e.g. ethnocentrism, conformity) can inhibit the transmission of pathogens; and so we hypothesize that collectivism (compared with individualism) will more often characterize cultures in regions that have historically had higher prevalence of pathogens. Drawing on epidemiological data and the findings of worldwide cross-national surveys of individualism/collectivism, our results support this hypothesis: the regional prevalence of pathogens has a strong positive correlation with cultural indicators of collectivism and a strong negative correlation with individualism. The correlations remain significant even when controlling for potential confounding variables. These results help to explain the origin of a paradigmatic cross-cultural difference, and reveal previously undocumented consequences of pathogenic diseases on the variable nature of human societies.

The, r = -0.69 at p-value 0.001 and n = 68. You can find the raw data here. It would be cool to see trends within nations/societies. For example, variation in altitude.

Related: Toxoplasma gondii & human culture.

Labels: human biodiversity

How Skin Color Is Determined:

In 2005 researchers identified a gene called SLC24A5 as a key determinant of skin color. Rebecca Ginger and colleagues now confirm that the protein product of this gene (NCKX5) is an ion exchanger; it exchanges sodium for calcium across a membrane, regulated by potassium. But unlike other NCKX proteins, they found that NCKX5 is not present on the cell surface, but internally in a compartment known as the trans-Golgi network. This compartment is where new proteins and vesicles are processed, modified and sorted.

When the researchers knocked out NCKX5 in melanocytes (the skin cells that manufacture the melanin pigment), melanin production decreased dramatically. They also demonstrated that changing the ancestral amino acid (alanine) at position 111 to the European form associated with lighter skintone (threonine) reduced NCKX5's exchanger activity.

Related: SLC24A5 and skin color.

Labels: Genetics

Reading Power and Plenty: Trade, War, and the World Economy in the Second Millennium by by Ronald Findlay and Kevin H. O'Rourke. So far somewhat like A Farewell to Alms, except painted on a much broader palette. I've read The Moral Consequences of Economic Growth, and though I wasn't convinced by all the specific examples the general thrust of that work makes sense. Nevertheless, I was still surprised when Findlay and O'Rourke connected the introduction of Champa rice strains and the cultural efflorescence of the Sung period. Say what? OK, this the logic, the new rice strains resulted in far greater productivity, and so China's population doubled in about 200 years, from 50 to 100 million. This 200 year period can be thought of as a transient between stationary states around the Malthusian limit. Findlay & O'Rourke don't focus much on the specific expressions of creativity during this period, but if you read much Chinese history you note that there was a lot of stuff going on during this period which set the tone for the next 1,000 years, from Neo-Confucianism to styles of landscape painting.

Labels: History

Pew is out with a new survey of religion in America. I've only skimmed it so far, but it has lots of interesting stuff. Note for example that this survey suggests that are marginally more self-identified Buddhists in America than Muslims (this is probably a function of the fact that Buddhism, and generally Buddhist ideas and concepts, have a much wider appeal to white Americans than Islam, whose "product" is less strong differentiated from forms of Christianity).

Check the methodology.

Via Rod Dreher.

Labels: Religion

I've been going into podcast overload lately, mainly because of this boing boing post. Wanted to alert you all to the high quality and interesting sound engineering of Radio Lab if you didn't know about it already. I've jammed the Memory, Placebo, and Stress episodes so far and was pleased overall with the level of informativeness, though I always prefer for brain regions to have names rather than descriptions. The Memory episode features Joe Ledoux and Karim Nader discussing the reconsolidation revival that occurred a few years ago.

In other news, The Sound of Young America has cool guests and The Rub has been doing a History of Hip Hop series that is worth your time.

Labels: podcasts

Roissy recently drew up a list of female skills for attracting males, and although it is clearly weighted toward succeeding in short-term relationships, the rank order seems about right for getting married too. One quick way to see what has mattered to men is to look for sexually dimorphic traits. As Darwin noted, such traits can have the flavor of "armaments," used to shove same-sex rivals out of the mating competition (such as deer antlers), or "ornaments" which attract mates (such as the peacock's tail), or both. I'll review some evidence that emotional vulnerability has been sexually selected in human females due to its attractiveness to males, rather than its use in female vs. female competition.

First, let's use YouTube to convince ourselves that emotional fragility makes a female more attractive, regardless of her physical appearance. Consider Emmylou Harris, Karen O, Elizabeth Fraser, or Hope Sandoval -- each is more desirable as a mate than if she were more tough-minded. In males, the attractiveness of fragility is conditional. If he can honestly signal manliness in dominating other males (however he does that), then emotional fragility around women may convince them that he's the best of both worlds. But if he lacks drive or ambition, then fragility will only make him appear needy and pathetic. Males who succeed here include Johnny Cash, Mike Ness, LL Cool J, and Joey Ramone.

Next, let me clarify the term "emotional fragility." It's a tendency to cry easily about something that would upset a caring person, a trait that will move men to protect and comfort her. More concretely, I'll treat it as a combination of the Big Five personality traits Neuroticism and Agreeableness, with more weight given to the former. A graph will help to illustrate [1]:


As for sex differences in these traits, see this previous post for a review of a meta-analysis by Costa et al. (2001). In brief, across all cultures of the world, females score higher than males on average for both Neuroticism and Agreeablness, though the magnitude depends on the physical and social environment that the population is adapted to: Europeans show huge sex differences, while Africans and East Asians show less pronounced differences. Among Europeans, the female mean is between 0.5 and 0.6 SD above the male mean for both Agreeableness and Neuroticism. A new cross-cultural survey by Schmitt et al. (2008) confirms this, although they find a slightly lower difference between means in Agreeableness. Both of these articles also provide good overviews of previous research.

While other personality traits show sex differences, Neuroticism and Agreeableness are by far the most dimorphic. Interestingly, in the first large-scale study designed to test changes in personality during adolescence, using a personality measure very comparable to an adult measure, McCrae et al. (2002) found a significant Time x Gender interaction effect for Neuroticism. During adolescence, females were much more likely to increase in Neuroticism than were males, in both the US and Belgium. Neuroticism declines for both sexes in the mid-20s, and drops even further by age 40. So, we observe a pattern of dimorphism that emerges just after puberty and gradually switches off beginning at the age when females would have had their first child. It is similar to physical attractiveness in females or muscularity in males, suggesting it has been sexually selected.

It is clear that fragility is unlikely to count as an "armament" used for same-sex competition, since it makes one more vulnerable to intimidation, teasing, and other forms of pushing one's same-sex rivals out of the mating market. We would expect it to be more of an "ornmament" that attracts mates, then. It may not make a female appear sexier, but when a girl starts to cry because she feels that she's become a burden to her friends and family, it may be nonsense, but a guy can't help but want to comfort her and protect her. Once she inevitably feels a little better, the guy will feel like he's performed his service as a man. And, modern malarkey aside, guys feel good when they do chivalrous and manly deeds, so that they would seek out women who offered the greatest opportunity to do so, and girls feel good when these acts are done for them. [2]

Moreover, comforting a female in need often involves close physical contact, such as holding her hand, holding her close and rubbing the upper part of her back, brushing the hair off of her face, or wiping the tears from her eyes. Physical bonding like this strengthens the relationship two people have, and also signals to her that the guy is a "protector of loved ones" (to borrow a phrase from the Mystery Method) -- a quality she is interested in during the years leading up to motherhood. It also tells her that he would take care of her if she became sick. So, it serves the dual purpose of attracting mates and detecting who among them is worth hanging onto.

[1] The fact that the Big Five uses the axes of low Neuroticism - high Neuroticism and low Agreeableness - high Agreeableness doesn't mean anything deep about how the traits are realized physiologically, or about how genes influence personality. We could rotate the old axes by, say, 45 degrees and come up a new set of two axes: a Tough-minded - Fragile dimension and a Cordial - Irascible dimension. The old traits of high A, low A, high N, and low N would lie in the quadrants of the new graph. In short, like a physicist, I'm perfectly free to chose my coordinate system to make life easy; I'm not claiming that things are different from how they're typically described.

[2] Of course, there is variation too -- some women succeed in the tough-minded niche and feel belittled when men try to do romantic things for them, and thus around whom men feel little motivation to behave in a chivalrous way. Roissy's many remarks about female lawyers serve as a good example of this.

Labels: babes and hunks, Personality

A recent article by D. S. and E. O. Wilson [1] has been acclaimed by some as reviving the fortunes of group selection. It must for a time have been available on the web (since I downloaded a pdf of the published version a month or so ago), but the closest thing I can find at present is this slightly different version submitted to (and presumably rejected by) Science in 2006. [Added: I should perhaps have mentioned that the two Wilsons are not related. No kin selection here!]


As gnxp's resident critic of group selection I feel an obligation to say something about the article, but I find the task dispiriting. Much of the Wilsons' article is a re-working of issues which have been debated many times before. (See e.g. my discussion here.) The debate has been largely about the most useful way of describing and classifying the phenomena, rather than about the biological facts. Hostility to group selectionism is provoked in part by the tendency of its advocates to claim for group selection a range of phenomena that other biologists regard as more usefully described in terms of inclusive fitness (kin selection). This hostility will not be allayed by such prominent assertions as:

During evolution by natural selection, a heritable trait that increases the fitness of others in the group (or the group as a whole) at the expense of the individual possessing the trait will decline in frequency within the group.

If the 'group' contains local concentrations of relatives (as it very often will), or if the trait preferentially affects relatives, this assertion is simply not correct. Did the Wilsons not notice this, or were they deliberately loading the dice against interpretations in terms of kin selection? Another potential confusion of the issues comes later in the article, where the Wilsons discuss insect eusociality. They argue strongly that between-colony selection is important in the evolution of eusocial insects, for example in traits such as nest construction. But whoever doubted it? Once eusociality (specialisation of reproduction) has been established, of course genetic variation and selection will often be between different colonies. The difficult question is how eusociality itself becomes established. The important insights into this have come from inclusive fitness theory, not group selectionism. (See for example chapter 11 of [2].)

Rather than spend more time on arid and abstract theoretical issues, I think it will be more rewarding to focus on a single empirical case, which the Wilsons themselves offer as a good example of the benefits of a multi-level approach. It can therefore serve as a test case of the benefits of that approach. The example I have chosen is the Wrinkly Spreader...




As the Wilsons describe this case,

the "wrinkly spreader" (WS) strain of Pseudomonas fluorescens evolves in response to anoxic conditions in unmixed liquid medium, by producing a cellulosic polymer that forms a mat on the surface. The polymer is expensive to produce, which means that non-producing 'cheaters' have the highest relative fitness within the group. As they spread, the mat deteriorates and eventually sinks to the bottom. WS is maintained in the total population by between-group selection, despite its selective disadvantage within groups, exactly as envisioned by multi-level selection theory.

I have followed up the Wilsons' reference for this case, and then some other citations. [Refs. 3, 4, and 5]

The facts of the WS case (stripped of theoretical baggage) seem to be as follows.

Pseudomonas fluorescens is a rod-shaped flagellated aerobic bacterium. It is found widely in the soil and in fresh water. In nature it is normally found as a single free-moving cell. In laboratory cultures, on the other hand, it often develops mutant strains which stick together rather than living singly. One of these is the Wrinkly Spreader strain, so-called because on slides of nutrient jelly it spreads out in sheets with a distinctive wrinkly appearance. In open containers (e.g. test tubes) of nutrient fluid the WS bacteria form a mat on the surface. Within about 10 days the mat becomes too heavy and sinks to the bottom. If the supply of nutrient is adequate, the process may be repeated, with new WS mats forming and eventually sinking.

Rainey and colleagues have studied the genetics of the WS strain.[3, 4 and 5] They have found that WS bacteria produce an excess of a cellulosic polymer which causes them to stick to each other and to surfaces. A side-effect of this is that they form a scum at the liquid-air interface (I presume this is a surface-tension effect, but the precise mechanism does not matter.) The production of the polymer uses scarce resources, so WS bacteria reproduce more slowly than non-WS bacteria in the same circumstances. However, this is offset by the advantage of being able to colonise the surface layer, with its better access to oxygen.

The description so far assumes that the mats on the surface contain only WS bacteria, usually derived from a single mutant individual. WS bacteria within the mat may however mutate in various ways which stop them overproducing the polymer, so that they revert to the ancestral phenotype. These mutants reproduce more quickly than the WS strain. They therefore tend to spread within the mats. But this weakens the structural integrity of the mats, which causes them to break up and sink more rapidly than the pure WS mats.

So what has this to do with group selection? What are the 'groups', and where is the 'selection'?

I think it will help to divide the cycle into two stages: before and after the emergence of non-WS mutants within the mats. At the beginning of the process, there are only single bacteria. Some of these mutate to the WS form, and literally stick together. Within the broth culture as a whole, WS mutants have lower fitness than the ancestral form, but the mutation gives them characteristics which enable them to predominate in a particular part of the ecosystem, i.e. the surface layer. Rainey et al. describe this as a form of 'cooperation', in which 'cooperation is costly to individuals, but beneficial to the group'. They note that the WS individuals are closely related (since they are descended from the same mutant individual) and describe the trait as spreading by 'kin selection'. This seems to me an unnecessary interpretation. The WS individuals in the surface layer are not sacrificing any fitness for the benefit of other individuals: they are simply using resources in a way that enables them to occupy this part of the environment. In a heterogeneous environment it can be misleading to average fitness over the entire range of sub-environments. For analogy, suppose a species of sheep ranges over a variety of altitudes. At higher altitudes the climate is colder, and the sheep need thicker fleece to live there in the winter. Sheep with mutations causing them to grow thicker fleece may have lower fitness than the average sheep, because it is costly to grow thick fleece, but at high altitudes the thick-fleeced variant may predominate because it is better adapted to that particular environment. Similarly, the WS strain is better-adapted to the surface layer. It is merely a coincidence that the adaptation involves the formation of 'groups'. We could imagine that instead of producing a polymer, and sticking together, the mutants produced little bubbles of gas which enabled them to float at the surface. In this case, no-one would dream of describing the process as either kin or group selection.

There is a more plausible case for appealing to group selection in the later stage of the process, when non-WS individuals have emerged within the WS mats. These individuals obtain the advantage of living in the surface layer without paying the cost. It is therefore reasonable to describe them as 'cheaters' or 'defectors'. They reproduce more rapidly, for a while, but in the longer term destroy the mats, to the detriment of all. According to the Wilsons, 'WS is maintained in the total population by between-group selection, despite its selective disadvantage within groups, exactly as envisioned by multi-level selection theory.' This is one possible interpretation of the facts, but it seems to me to go beyond the evidence presented by Rainey et al. We should note (as the Wilsons do not) that all surface mats collapse within a few days, whether or not they contain defectors. The regeneration of surface mats then depends on the establishment of a new population of WS individuals at the surface. These could emerge either by new mutations from the ancestral form, or from fragments of the collapsing WS mats. (It is not clear from the papers I have seen which of these usually occurs.) Either way, the Wilsons' description is incomplete. It implies that some WS 'groups' (the ones without defectors) survive indefinitely, while others fail. This is not the case. Even if a description in terms of group selection is formally valid, it does not (in my opinion) add much of value to the understanding of the phenomena. And if this is one of the best examples of group selection that its advocates can find, one cannot have much confidence in the others. (And indeed, some of the others, like the Wilsons' reference to the territorial behaviour of female lions, seem even worse. How can anyone sensibly discuss this without mentioning that the lionesses of a pride are usually closely related? [6, p. 37])

This is not to say that an account in terms of group selection will never provide useful insights into evolutionary processes. The evolution of disease organisms such as Myxomatosis seems to be one very plausible example. But the Wilsons' article does not persuade me that group selection, as distinct from inclusive fitness, is more than a minor wrinkle on the face of evolutionary theory.


References:

[1] D. S. and E. O. Wilson: 'Rethinking the Theoretical Foundation of Sociobiology', Quarterly Review of Biology, December 2007, vol. 82. No.4, 327-348.

[2] J. Maynard Smith and E. Szathmary: The Origins of Life: from the birth of life to the origins of language, 1999

[3] P. B. and K. Rainey: 'Evolution of cooperation and conflict in experimental bacterial populations', Nature, 425, 2003, 72-4.

[4 P. B. and K. Rainey: 'Adaptive radiation in a heterogeneous environment', Nature, 394, 1998, 69-72.

[5] A. J. Spiers et al.: 'Adaptive divergence in experimental populations of Pseudomonas fluorescens. I: Genetic and phenotypic bases of Wrinkly Spreader fitness', Genetics, 161, 2002, 33-46.

[6] G. B. Schaller: The Serengeti Lion, 1972.

Labels: Genetics

The other day I was wondering whatever happened to A New Kind of Science. Well, Stephen Wolfrom is on the latest bloggingheads.tv.

An In-Depth Look at Genetic Variation, covers Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation (about ~15 minutes long, interview with Rick Myers). Also, Wired blogs the most recent spate of papers (and gets a sound-bite from Marcus Feldman)....

Update: Readers might appreciate this from the Science paper:

However, the between-population variance is sufficient to reveal consistent population structure because subtle but nonrandom differences between populations accumulate over a large number of loci and yield principal components that can account for a major portion of the variation (21).

What's reference "21"? A. W. Edwards, Bioessays 25, 798 (2003). Human Genetic Diversity: Lewontin's Fallacy. Ding, dong....


(A figure from the Science paper below the fold)

Labels: Genetics

Cool paper in Nature, Global trends in emerging infectious diseases. Not cool because infectious diseases are great, but I believe they've been (and are) major evolutionary pressures on our species. Great map too. From the legend:

a) zoonotic pathogens from wildlife
b) zoonotic pathogens from non-wildlife
c) drug-resistant pathogens
d) vector-borne pathogens

Not surprised about the intersection with world population density. Just by inspection, the Indo-Gangetic plain looks to be the "winner" here! Though it does seem that Sub-Saharan Africa holds its own in terms of representing above its population-weight class in the wild-life derived and vector-born pathogen categories. Might we be able to chalk that up to a long history of coevolution between the African ecosystem and hominid species? Domesticated animals seem to be more of an issue in the old Eurasian Oikumene as you would expect. For more precision on the global trends and correlates, check out their regressions.

Labels: pathogens

This is a post for Google. A post I wish had been there for me during my periods of confusion on this topic. I notice that Chris Roach recently referred to Robert J. Samuelson as a "Respected economist." He isn't. Robert J. Samuelson is a financial and economic journalist. He has bachelor's degree in government from Harvard, so one assumes he has taken an economics course or two or three. Samuelson has a column in Newsweek which often focuses on economics; this means that he is a major public figure in this area. I had assumed that Robert J. Samuelson was a prominent economist who was moonlighting as a journalist until a few years ago when I was curious if he was related to Larry Summers. I knew Summers was related to an economist with the last name Samuelson. I think this is a reason that people assume that Robert J. Samuelson is an economist. Paul A. Samuelson is obviously an economist, to some extent the economist of the 20th century (along with Kenneth Arrow and a few others). When I didn't know anything about economics I too believed that Robert J. Samuelson was an economist partly because I vaguely knew Paul A. Samuelson was the economist, which says a lot about how eminent Paul A. Samuelson must be if I had any awareness of the man!

Labels: Economics

I've been reading a fair amount of economic history and political economy recent (e.g., A Concise Economic History of the World, The Moral Consequences of Economic Growth and Angus Maddison's substantial body of work). I've read a few micro & macro texts so I come into this with some vague theoretical understanding of the framework which economists are marinated in, and of course I know about comparative advantage and am broadly sympathetic to globalization. The analytic sharpness that economics brings to broad historical questions is illuminating. That being said, on occasion there are comments which make me wonder about the excessive simplicity of the economic narrative.

Consider the case of two nations which trade with each other. One nation starts out far wealthier. Businesses in the wealthier nation relocate some factories to the poorer nation. This increases aggregate utility, consumers in the wealthy nation can now purchase cheaper products, while a substantial number of workers in the poorer nation are more well off than they otherwise would be. But, there's an issue here, inequality is likely to increase within the nations. Overall inequality in the aggregate has decreased, the poorer nation is now far wealthier and so the income gap is not as stark across national boundaries. But a minority of those who had factory jobs in the wealthy nation now might have to shift to lower paying service sector employment. Additionally, income inequality might initially also increase in the poorer nation as some are left behind (though as economic development proceeds one might suppose that the lower orders would catch up).

As someone who lives in a relatively wealthy nation let's just consider that case. I'm not sure if I'm particularly reassured that aggregate utility has increased across the world while a bunch of factory workers now go unemployed or are marginally employed. It's not that I'm a particularly empathetic person, I'm not, but perhaps I'll run into these people in the subway or at the shopping mall. It's great that people in a far off country are now wealthier and also increase my own access to more baskets of goods; but I can't but help be a little worried about idle hands and potential riots in the streets from the "victims" of the redistribution of economic activity. More immediately, what's the point in my being able to purchase more bling if it only invites a mugging at hands of the victims of globalization?

I have Joseph Stiglitz's Making Globalization Work on my "to read" list, so perhaps my qualms will be addressed at some point. So far I'm not reassured that economists truly internalize the structural biases in human psychology when talking about these macro-level issues. It seems that in universal suffrage democracies the political class always has to pretend as if comparative advantage doesn't exist and mouth populist slogans, but they always favor globalization when it comes to implementing policy (at least over the long term). At this point most humans understand that the the earth is not at the center of the solar system; but it seems to me that that is an easier concept to grasp than the logic of economics, in part because human intuitions about social facts and dynamics are very strong and persistent in the face of intellectual persuasion.

Note: Feel free to recommend books on economic history in the comments. Douglass North is also on my "to read."

Labels: Economics

Natural selection and cultural rates of change (Open Access).

As a follow up to Assman's last post I was thinking I should link to this article from Asian-Nation which parses Census 2000 data on interracial marriage of various Asian American groups. Do read the article (caveats appropriate to identity politics organs), but I just took their data and placed it below the fold. Also, I modified it a little and added the ratios of men to women who marry whites by generation and immigration status. That is, the Census broke up individuals according to whether they were immigrants, or US-raised or born. There are some caveats with analyzing the data in that way; Asian Indians and Vietnamese have only 1 US-raised or born generation which is actually marrying right now. These groups are post-1965, in contrast to Japanese Americans, who are predominantly US-raised or born, with many 3rd, 4th and 5th generation individuals. With that stated, I was surprised at the relatively moderate sex ratios when you constrain marriages only to those where both partners are non-immigrants; i.e., pretty much acculturated as Americans. Arguably the most assimilated Asian American group on this list, the Japanese, have the second most balanced sex ratio, 0.829 between males and females in outmarriage to whites. Why the most second balanced? Asian Indians are tops in terms of balance. In fact, when you look at all marriages men outmarry somewhat more than women in this group. But Asian Indians are a bit different than the others on the list in a whole lot of ways. Look at the very low marriage rates to "Other Asians" for example. These might even include Pakistanis, Bangladeshis, etc., overstating intermarriage with the other groups on the list. The full table below the fold....

Marriage Patterns for Six Largest Asian American Ethnic Groups (Oct. 2007), Source Asian-Nation
	All spouses	US born/raised X US born or foreign born	US born/raised X US born/raised
Asian Indians
Men	(All) Male : female outmarriage ratio - 1.28 (All US born) Male : female outmarriage - 0.862
Asian Indian	91.9	73.3	56.7
Other Asian	0.9	2.7	2.8
White	5.5	18.5	31.3
Black	0.5	0.5	0.8
Hispanic/Latino	0.8	3.4	5.8
Multiracial & All Others	0.4	1.6	2.7
Women
Asian Indian	93.6	77.5	54.2
Other Asian	0.7	1.7	2.0
White	4.3	18.9	36.3
Black	0.5	1.4	2.8
Hispanic/Latino	0.4	1.4	2.7
Multiracial & All Others	0.5	0.9	1.9
Chinese
Men	(All) Male : female outmarriage ratio - 0.381 (All US born) Male : female outmarriage - 0.735
Chinese	89.5	64.6	53.1
Other Asian	4.5	11.5	11.6
White	5.3	20.2	29.7
Black	0.1	0.3	0.5
Hispanic/Latino	0.7	2.1	3.0
Multiracial & All Others	0.4	1.4	2.0
Women
Chinese	81.5	54.0	44.6
Other Asian	2.7	7.3	7.8
White	13.9	32.8	40.4
Black	0.4	0.9	1.1
Hispanic/Latino	0.9	2.9	3.5
Multiracial & All Others	0.6	2.1	2.6
Filipinos
Men	(All) Male : female outmarriage ratio - 0.338 (All US born) Male : female outmarriage - 0.779
Filipino	82.4	50.1	35.6
Other Asian	2.8	6.9	7.3
White	9.2	27.1	36.0
Black	0.3	1.2	1.3
Hispanic/Latino	2.9	8.3	11.1
Multiracial & All Others	2.3	6.3	8.4
Women<