Daily Data Dump (Friday)

Hope the weather is good enough where you are that you’ll enjoy the weekend.

Tories Still Short of a Majority: Hix-Vivyan Prediction up to 26 April. Trendlines + 95% confidence intervals as shading. What’s not to like?

Tolerance and Tension: Islam and Christianity in Sub-Saharan Africa. In 1900 there were 50% fewer Christians than Muslims in Africa. In 1950 there were as many Christians as Muslims in Sub-Saharan Africa. Today there are twice as many Christians as Muslims. Christ was a black man, while Muhammad had white thighs.

Listening to (and Saving) the World’s Languages. I don’t get why there are always “languages of the world are dying” articles popping up regularly in the mainstream and scientific media. I mean there’s a great benefit to having one language unify diverse groups. It’s just like how Europeans gained efficiencies by ditching their local currencies and going with the Euro. Eh, well, perhaps not the best example right now….

What can you learn from a whole genome sequence? Dr. Daniel MacArthur seems to suggest that there isn’t a whole lot more you can learn that you couldn’t learn from a chip with hundreds of thousands of SNPs instead of all 3 billion base pairs. Seems about right. And remember the baseline, many people are highly skeptical of the marginal value of the SNP chips beyond what you’d know from your family history.

Absence of Evidence for MHC–Dependent Mate Selection within HapMap Populations. I’m starting to lean away from thinking that the MHC studies in humans are finding any real robust correlations. The studies are literally all over the place, with reverse signs of statistically significant correlations in some cases.

When America was post-colonial

Below I stated:

…until the late 20th century the majority of the ancestry of the white population of the republic descended from those who were counted in the 1790 census.

A commenter questioned the assertion. The commenter was right to question it. My source was a 1992 paper that estimated that only in 1990 did the proportion of American ancestry which derived from those who arrived after the 1790 census exceeding 50%. In other words, if you ran the ancestors of all Americans back to 1790, a majority of that set would have been counted in the 1790 census (so people of mixed ancestry would contribute to the two components are weighted by their ancestry).

The major issue here is that there is a difference between whites, and non-whites, especially before mass Asian and Latin American immigration post-1965, when white vs. non-white ~ white vs. black. Almost all the ancestors of black Americans who were black were already resident in the United States in 1790. A few years ago I read up on the history of American slavery and was surprised how genuinely indigenous the black American, slave and free, population was by the late 18th century (English speaking and Christian). There was an obvious reason why Southern slave-holders went along with the ban on importation of slaves which was due to kick in in the early decades of the republic: American blacks, unlike slave populations elsewhere in the New World, had endogenous natural increase. This explains part of the relative paucity of African aspects in their culture in relation to the blacks of Haiti or Brazil, where African-born individuals were still very substantial numerically at emancipation because of high attrition rates (it is sometimes asserted that the majority of blacks liberated during the Haitian Revolution were born in Africa. Likely a hyperbole, but it gets across the strength of connection).

In any case, to estimate the white proportion attributable to 1790, I have to correct for the black proportion within the total. As an approximation I think it’s acceptable to simply attribute blacks as a whole to the proportion which had ancestors here in 1790 in full. I suspect a greater proportion of the black ancestry which post-dates 1790 would come from the white component of their heritage which simply isn’t of notice in American society for various reasons in any case (Henry Louis Gates Jr. is more white than he is black in terms of ancestry, but he’s the doyen of Africana Studies). So, assuming that blacks contribute to the 1790 and before component in full, I estimate that between 1910 and 1920 the majority of the ancestry of the white population shifted from 1790 and before, to after. Specifically, in 1910 51% of the ancestry could be traced to 1790 and before among whites, and in 1920 49%. In 1950 it was 47% 1790 and before. So I should have said early 20th century, not late. I wouldn’t be surprised though if the balance has started to shift in recent years, as many “white ethnic” groups (Jews, Italians, Irish, etc.) are more heavily concentrated in urban areas, while the most fertile white community in the United States, the Mormons of Utah, are also the most Old Stock Yankee in ancestry (I am aware that many Mormons are descended from European immigrants who converted in Europe and made the journey after conversion, but Mormons are still far more Old Stock Yankee than any group outside of interior New England).

Men & ideas on the move: settled lands & colonized minds

I am currently reading Peter Heather’s Empires and Barbarians: The Fall of Rome and the Birth of Europe. This is a substantially more hefty volume in terms of density than The Fall of the Roman Empire: A New History of Rome and the Barbarians . It is also somewhat of a page turner. One aspect of Heather’s argument so far is his attempt to navigate a path between the historically tinged fantasy of what its critics label the “Grand Narrative” of mass migration of barbarian tribes such as the Goths, Vandals and Saxons during the 4th to 6th centuries, dominant before World War II, and its post-World World II counterpoint. As a reaction against this idea archaeologists have taken to a model of pots-not-people, whereby cultural forms flow between populations, and identities are fluid and often created de novo. This model would suggest that only a tiny core cadre of “German” “barbarians” (and yes, often in this area of scholarship the most banal terms are problematized and placed in quotations!) entered the Roman Empire, and the development of a Frankish ruling class in the former Gaul, for example, was a process whereby Romans assimilated to the Germanic identity (with the shift from togas to trousers being the most widespread obvious illustration of Germanization of norms). I believe that liberally applied this model is fantasy as well. Being a weblog where genetics is important, my skepticism of both extreme scenarios is rooted in new scientific data.

There are cases, such as the Etruscans, where the migration is clear from the genetics, both human and their domesticates. The peopling of Europe after the last Ice Age is now very much an open question. The likelihood that the present population of India is the product of an ancient hybridization event between an European-like population and an indigenous group with more affinity with eastern, than western, Eurasian groups, is now a rather peculiar prehistoric conundrum. It also seems likely that the spread of rice farming in Japan was concomitant with the expansion of a Korea-derived group, the Yayoi, at the expense of the ancient Jomon people. And yet there are plenty of inverse cases. The spread of Latinate languages and Romanitas did not seem to perturb the basic patterns of genetic relationship among the peoples of Europe. The emergence of the Magyar nation on the plains of Roman Pannonia seems to have involved mostly the Magyarization of the local population. In contrast, the Bulgars were totally absorbed by their Slavic subjects culturally, leaving only their name. The spread of the Arabic language and culture was predominantly one of memes, not genes (clearly evident in the current dynamic of Arabization in parts of the Maghreb).

And yet you will note that there is a slight difference between the few examples I’ve cited: population replacement seems to have occurred in the more antique cases, rather than the more recent ones. This would naturally bias the perspectives of historians, who have much more data on more recent events (no offense, but archaeologists seem to be able to say whatever they want!). The Etruscan language itself is known only from fragments, while the happenings in prehistoric Europe and India can only be inferred very indirectly. I now offer a modest hypothesis for the distinction, why in some cases is it just the “pots” which move (Arabs), and in other cases it is the people who move (the Japanese). In cases of population replacement there is often a shift in mode of production. In cases where there is the diffusion of culture it is often a system or set of ideas which rent-seeking elites can exploit to maintain their position, or perpetuate it, flow across space. Islam was not only a potent ideology which bound the tribes of Arabia together so that they could engage in collective action, local elites across the new Muslim-dominated world found it a congenial international system whereby they could integrate themselves into a civilization of elite peers, as well as justify their god-given position at the apex of the status hierarchy (granted, many had this in the form of Christianity or Zoroastrianism, but once the old top dogs were overthrown the benefit of these systems was considerably less). The spread of Yayoi culture in Japan involved a shift from more extensive, toward more intensive, forms of agriculture. Their population base was greater, and the domains of the Jomon were left “underexploited” from the perspective of the more productive mode of agriculture which the Yayoi were engaged in. It need not be an issue of mass slaughter or extermination, a high endogenous rate of natural increase as well as disease, combined with assimilation and co-option of local elites, could result in the swallowing up of a population engaged in a less intensive mode of production. This sort of hybrid aspect of cultural and genetic expansion, whereby the local substrate is assimilated and synthesized with the expanding ethnic group, seems to be a good fit to the pattern that we see among the Han of China.

But shifts from modes of production exhibit some level of discontinuity, insofar as there are diminishing returns once all the land appropriate for that mode of production has been taken over. Farmers who are expanding into land held by hunter-gatherers or those practicing less intensive forms of agriculture can have enormous rates of natural increase because they’re not bound by Malthusian constraints. This is evident in the United States, until the late 20th century the majority of the ancestry of the white population of the republic descended from those who were counted in the 1790 census. The reason had to do with the extremely high birthrates among white Americans. When regions such as New England were “filled up,” they pushed out to the “frontier,” to northern Ohio, then to the Upper Midwest, and finally the Pacific Northwest. And in the process there was a radical change in the genetic variation of North America, as the indigenous populations died from disease, were numerically overwhelmed, or genetically absorbed. This is an extreme case scenario, but I think it illustrates what occurs when modes of production collide, so to speak. The pattern in Latin America was somewhat different, though an amalgamated Mestizo population did emerge over time, there was not the wholesale demographic replacement in many regions. And I believe that the reason is that the Iberians did not bring a superior mode of production, rather, the large local population base engaged in agriculture presented an opportunity for rent-seekers to place themselves atop the status hierarchy. Sometimes this involved intermarriage with local elites, as was the case in Peru where the nobility of the Inca intermarried with the Spanish conquistadors for the first few generations (the whiteness of the Peruvian elite despite the fact that the old families have Inca ancestry is simply due to dilution as successive generations of lower Spanish nobility set off to the New World and married into Creole families).

By the Roman period I believe that much of the core Old World was “filled up” in terms of intensive agricultural production. So most, though not all, of the changes in ethnicity or identity are biased toward elite emulation and novel identity formation. The Turks did not bring an innovative new economic system whereby they replaced the Greek and Armenian peasantry in Anatolia, rather, on the contrary peculiarities in the Turkish Ottoman system of rule produced a situation where the old families were usually replaced in positions of power by converts from the Christian groups who assimilated to a Turkish identity. When the economic arrangements reach stasis and the population is at Malthusian equilibrium change is a matter of shifting identities and affinities of the rent-seekers. When radically new economic systems emerge, opportunities for disparate population growth present themselves. Ergo, England went from being demographically dwarfed by France in the 17th century, to surpassing it in population in the 19th. England was of course the first nation to break into a new mode of production since the agricultural revolution.

Credit: Thanks to Michael Vassar for triggering this line of reasoning after a conversation we had about the Neolithic revolution.

European man perhaps not a Middle Eastern farmer

A few months ago I blogged a paper in PLoS Biology which suggested that a common Y chromosomal haplogroup, in fact the most common in Europe and at modal frequency along the Atlantic fringe, is not pre-Neolithic. Rather their analysis of the data implied that the European variants were derived from an Anatolian variant. The implication was that a haplogroup which had previously been diagnostic of “Paleolithicness,” so to speak, of a particular population may in fact be an indication of the proportion of Neolithic Middle Eastern ancestry. The most interesting case were the Basques, who have a high frequency of this haplogroup, and are often conceived of as “ur-Europeans,” Paleolithic descendants of the Cro-Magnons in the most romantic tellings. I was somewhat primed to accept this finding because of confusing results from ancient DNA extraction which implies a lot of turnover in maternal lineages, the mtDNA. My logic being that if the mtDNA exhibited rupture, then the Y lineages should too, as demographic revolutions are more likely to occur among men.

But perhaps not. A new paper in PLoS ONE takes full aim at the paper I blogged above. It is in short a purported refutation of the main finding of the previous paper, and a reinstatement of what had been the orthodoxy (note the citations to previous papers). A Comparison of Y-Chromosome Variation in Sardinia and Anatolia Is More Consistent with Cultural Rather than Demic Diffusion of Agriculture:

Two alternative models have been proposed to explain the spread of agriculture in Europe during the Neolithic period. The demic diffusion model postulates the spreading of farmers from the Middle East along a Southeast to Northeast axis. Conversely, the cultural diffusion model assumes transmission of agricultural techniques without substantial movements of people. Support for the demic model derives largely from the observation of frequency gradients among some genetic variants, in particular haplogroups defined by single nucleotide polymorphisms (SNPs) in the Y-chromosome. A recent network analysis of the R-M269 Y chromosome lineage has purportedly corroborated Neolithic expansion from Anatolia, the site of diffusion of agriculture. However, the data are still controversial and the analyses so far performed are prone to a number of biases. In the present study we show that the addition of a single marker, DYSA7.2, dramatically changes the shape of the R-M269 network into a topology showing a clear Western-Eastern dichotomy not consistent with a radial diffusion of people from the Middle East. We have also assessed other Y-chromosome haplogroups proposed to be markers of the Neolithic diffusion of farmers and compared their intra-lineage variation—defined by short tandem repeats (STRs)—in Anatolia and in Sardinia, the only Western population where these lineages are present at appreciable frequencies and where there is substantial archaeological and genetic evidence of pre-Neolithic human occupation. The data indicate that Sardinia does not contain a subset of the variability present in Anatolia and that the shared variability between these populations is best explained by an earlier, pre-Neolithic dispersal of haplogroups from a common ancestral gene pool. Overall, these results are consistent with the cultural diffusion and do not support the demic model of agriculture diffusion.

Their main trump cards seem to be that they used a denser set of markers, and, they claim they have a more accurate molecular clock. Ergo, in the latter case they produce a better time to the last common ancestor, which is twice as deep as the paper they’re attempting to refute. Someone like Dienekes or Polish Genetics can tackle the controversies in scientific genealogy here (I know Dienekes has a lot of interest in mutational rates which go into the molecular clock for these coalescence times). Rather, I would suggest that usage of Sardinians concerns me for an obvious reason: they’re genetic outliers in Europe. A lot of this has to do with being an island. Islands build up uniqueness because they don’t engage in the normal low level gene flow between adjacent populations because they’re…well, islands. You would know about Sardinia’s position because they’re one of the populations in L. L. Cavalli-Sforza’s HGDP sample and they show up in History & Geography of Human Genes as on the margins of the PCA plots. But here’s a figure from a more recent paper using a much denser market set, constrained to Southern European populations. I labelled some of the main ones so you’d get a sense of why I say Sardinians are outliers:
sardin

Over the two largest independent dimensions of genetic variation you can see a distribution from the southeast Mediterranean all the way to the northwest (in fact, the Basques are an Atlantic group). The Sardinians are out of the primary axis, and that’s why I say they’re an outlier. A few other European groups, like the Icelanders and Sami exhibit this tendency. As I suggested above I think the fact that the Sardinians are on an isolated island relatively far from the European and Africa mainland means that they’ll “random walk” in genetic variation space toward an outlier status naturally, just as the Icelanders have since the year 1000. So though I grant the authors their rationale for using the Sardinians as a reference against the Anatolian source population, the fact that we know that they’re peculiar in their variation in total genome content makes me wary of drawing too many inferences from their relationships to other groups where they are seen as representative of a larger set.

Citation: Morelli L, Contu D, Santoni F, Whalen MB, & Francalacci P (2010). A Comparison of Y-Chromosome Variation in Sardinia and Anatolia Is More Consistent with Cultural Rather than Demic Diffusion of Agriculture PLoS ONE : 10.1371/journal.pone.0010419

Daily Data Dump (Thursday)

Experiments in cultural transmission and human cultural evolution. I’ve read plenty of models of cultural evolution (Cavalli-Sforza & Feldman, Boyd & Richerson, come to mind), but a post which reviews some more empirical literature. One criticism of modelers of cultural evolution is that they’re all talk, no action, and so basically just mathed up versions of armchair humanists.

Wired for Sex. The existence of two sexes is of obvious evolutionary genetic interest; males are an “expensive” cost for a lineage. But obviously there are other angles to explore, including neurological. Because sexual dimorphism takes a while to evolve I think one possible way to get a good grip on sex differences in the brain might be to look at male vs. female anatomy, function and neuochemistry across the great apes + humans. Presumably many of the differences are basal characteristics.

Psychopaths and Rational Morality. Would Mr. Spock have been a psychopath?

The Arc of Evolution Is Long and Rarely Bends Towards Advantageous Alleles: Why Does Popular Science Ignore Neutral Theory? Love the title. I think writing a book like “Climbing Mount Improbable” is going to be easier than writing “Probably Random Walking All Over.”

Can’t Pivot to the Economy With Magic. I disagree. It’s a world filled with magic & mystery, we need to just open our eyes and appreciate it. We can can use magic & mystery as fuel to generate productivity gains. A wizard in every home I say!

Possible instance of genetic discrimination

Dr. Daniel MacArthur pointed me to this story, Conn. woman alleges genetic discrimination at work:

A Connecticut woman who had a voluntary double mastectomy after genetic testing is alleging her employer eliminated her job after learning she carried a gene implicated in breast cancer.

Pamela Fink, 39, of Fairfield said in discrimination complaints that her bosses at natural gas and electric supplier MXenergy gave her glowing evaluations for years, but targeted, demoted and eventually dismissed her when she told them of the genetic test results.

Her complaints, filed Tuesday with the U.S. Equal Opportunity Commission and Connecticut Commission on Human Rights and Opportunities, are among the first known to be filed nationwide based on the federal Genetic Information Nondiscrimination Act.

What probability do readers put in regards to this being a legitimate complaint? This seems a large firm, so I doubt that group insurance rates would change because of one person (I have heard of this occurring in small businesses where an expensive employee or employee’s family member can effect the rate for everyone else). So if it is legitimate the main issue would have been their fear of future illness, but the woman in question went through a double mastectomy, which I assume would obviate that concern. What am I missing? Are there expectations that she’d be taking medical leave in the future due to follow up operations or treatment?

Update: Brendan Maher has some follow up from Fink’s lawyer.

Modeling the probabilities of extinction

Change is quite in the air today, whether it be climate change or human induced habitat shifts. What’s a species in the wild to do? Biologists naturally worry about loss of biodiversity a great deal, and many non-biologist humans rather high up on Maslow’s hierarchy of needs also care. And yet species loss, or the threat of extinction, seems too often to impinge upon public consciousness in a coarse categorical sense. For example the EPA classifications such as “threatened” or “endangered.” There are also vague general warnings or forebodings; warmer temperatures leading to mass extinctions as species can not track their optimal ecology and the like. And these warnings seem to err on the side of caution, as if populations of organisms are incapable of adapting, and all species are as particular as the panda.

That’s why I pointed to a recent paper in PLoS Biology, Adaptation, Plasticity, and Extinction in a Changing Environment: Towards a Predictive Theory below. I am somewhat familiar with one of the authors, Russell Lande, and his work in quantitative and ecological genetics, as well as population biology. I was also happy to note that the formal model here is rather spare, perhaps a nod to the lack of current abstraction in this particular area. Why start complex when you can start simple? Here’s their abstract:

Many species are experiencing sustained environmental change mainly due to human activities. The unusual rate and extent of anthropogenic alterations of the environment may exceed the capacity of developmental, genetic, and demographic mechanisms that populations have evolved to deal with environmental change. To begin to understand the limits to population persistence, we present a simple evolutionary model for the critical rate of environmental change beyond which a population must decline and go extinct. We use this model to highlight the major determinants of extinction risk in a changing environment, and identify research needs for improved predictions based on projected changes in environmental variables. Two key parameters relating the environment to population biology have not yet received sufficient attention. Phenotypic plasticity, the direct influence of environment on the development of individual phenotypes, is increasingly considered an important component of phenotypic change in the wild and should be incorporated in models of population persistence. Environmental sensitivity of selection, the change in the optimum phenotype with the environment, still crucially needs empirical assessment. We use environmental tolerance curves and other examples of ecological and evolutionary responses to climate change to illustrate how these mechanistic approaches can be developed for predictive purposes.


Their model here seems to be at counterpoint to something called “niche modelling” (yes, I am not on “home territory” here!), which operates under the assumption of species being optimized for a particular set of abiotic parameters, and focusing on the shifts of those parameters over space and time. So extinction risk may be predicted from a shift in climate and decrease or disappearance of potential habitat. The authors of this paper observe naturally that biological organisms are not quite so static, they exhibit both plasticity and adaptiveness within their own particular life history, as well as ability to evolve on a population wide level over time. If genetic evolution is thought of as a hill climbing algorithm I suppose a niche model presumes that the hill moves while the principal sits pat. This static vision of the tree of life seems at odds with development, behavior and evolution. The authors of this paper believe that a different formulation may be fruitful, and I am inclined to agree with them.

journal.pbio.1000357.e001As I observed above the formalism undergirding this paper is exceedingly simple. On the left-hand side you have the variable which determines the risk, or lack of risk, of extinction more or less, because it defines the maximum rate of environmental change where the population can be expected to persist. This makes intuitive sense, as extremely volatile environments would be difficult for species and individual organisms to track.Too much variation over a short period of time, and no species can bend with the winds of change rapidly enough. Here are the list of parameters in the formalism (taken from box 1 of the paper):

ηc – critical rate of environmental change: maximum rate of change which allows persistence of a population

B – environmental sensitivity of selection: change in the optimum phenotype with the environment. It’s a slope, so 0 means that the change in environment doesn’t change optimum phenotype, while a very high slope indicates a rapid shift of optimum. One presumes this is proportional to the power of natural selection

T – generation time: average age of parents of a cohort of newborn individuals. Big T means long generation times, small T means short ones

σ2 – phenotypic variance

h2 – heritability: the proportion of phenotypic variance in a trait due to additive genetic effects

rmax intrinsic rate of increase: population growth rate in the absence of constraints

b – phenotypic plasticity: influence of the environment on individual phenotypes through development. Height is plastic; compare North Koreans vs. South Koreans

γ – stabilizing selection: this is basically selection pushing in from both directions away from the phenotypic optimum. The stronger the selection, the sharper the fitness gradient. Height exhibits some shallow stabilizing dynamics; the very tall and very short seem to be less fit

Examining the equation, and knowing the parameters, some relations which we comprehend intuitively become clear. The larger the denominator, the lower the rate of maximum environmental change which would allow for population persistence, so the higher the probability of extinction. Species with large T, long generation times, are at greater risk. Scenarios where the the environmental sensitivity to selection, B, is much greater than the ability of an organism to track its environment through phenotypic plasticity, b, increase the probability of extinction. Obviously selection takes some time to operate, assuming you have extant genetic variation, so if a sharp shift in environment with radical fitness implications occurs, and the species is unable to track this in any way, population size is going to crash and extinction may become imminent.

On the numerator you see that the more heritable variation you have, the higher ηc. The rate of adaptation is proportional to the amount of heritable phenotypic variation extant within the population, because selection needs variance away from the old optimum toward the new one to shift the population central tendency. In other words if selection doesn’t result in a change in the next generation because the trait isn’t passed on through genes, then that precludes the population being able to shift its median phenotype (though presumably if there is stochastic phenotypic variation from generation to generation it would be able to persist if enough individuals fell within the optimum range). The strength of stabilizing selection and rate of natural increase also weight in favor of population persistence. I presume in the former case it has to do with the efficacy of selection in shifting the phenotypic mean (i.e., it’s like heritability), while in the latter it seems that the ability to bounce back from population crashes would redound to a species’ benefit in scenarios of environmental volatility (selection may cause a great number of deaths per generation until a new equilibrium is attained).

journal.pbio.1000357.e002Of course a model like the one above has many approximations so as to approach a level of analytical tractability. They do address some of the interdependencies of the parameters, in particular the trade-offs of phenotypic plasticity. In this equation 1/ω2b quantifies the cost of plasticity, r0 represents increase without any cost of plasticity. We’re basically talking about the “Jack-of-all-trades is a master of none” issue here. In a way this crops up when we’re talking of clonal vs. sexual lineages on an evolutionary genetic scale. The general line of thinking is that sexual lineages are at a short-term disadvantage because they’re less optimized for the environment, but when there’s a shift in the environment (or pathogen character) the clonal lineages are at much more risk because they don’t have much variation with which natural selection can work. What was once a sharper phenotypic optimum turns into a narrow and unscalable gully.

Figure 2 illustrates some of the implications of particular parameters in relation to trade-offs:

paramslande

There’s a lot of explanatory text, as they cite various literature which may, or may not, support their model. Clearly the presentation here is aimed toward goading people into testing their formalism, and to see if it has any utility. I know that those who cherish biodiversity would prefer that we preserve everything (assuming we can actually record all the species), but reality will likely impose upon us particular constraints, and trade-offs. In a cost vs. benefit calculus this sort model may be useful. Which species are likely to be able to track the environmental changes to some extent? Which species are unlikely to be able to track the changes? What are the probabilities? And so forth.

I’ll let the authors conclude:

Our aim was to describe an approach based on evolutionary and demographic mechanisms that can be used to make predictions on population persistence in a changing environment and to highlight the most important variables to measure. While this approach is obviously more costly and time-consuming than niche modelling, its results are also likely to be more useful for specific purposes because it explicitly incorporates the factors that limit population response to environmental change.

The feasibility of such a mechanistic approach has been demonstrated by a few recent studies. Deutsch et al…used thermal tolerance curves to predict the fitness consequence of climate change for many species of terrestrial insects across latitudes, but without explicitly considering phenotypic plasticity or genetic evolution. Kearney et al…combined biophysical models of energy transfers with measures of heritability of egg desiccation to predict how climate change would affect the distribution of the mosquito Aedes aegiptii in Australia. Egg desiccation was treated as a threshold trait, but the possibility of phenotypic plasticity or evolution of the threshold was not considered. These encouraging efforts call for more empirical studies where genetic evolution and phenotypic plasticity are combined with demography to make predictions about population persistence in a changing environment. The simple approach we have outlined is a necessary step towards a more specific and comprehensive understanding of the influence of environmental change on population extinction.

Citation: Chevin L-M, Lande R, & Mace GM (2010). Adaptation, Plasticity, and Extinction in a Changing Environment: Towards a Predictive Theory PLoS Biol : 10.1371/journal.pbio.1000357

The confusions of definitions across borders

blackheadofstateJust reading this article in Slate, How To Throw an Election:

On paper, that’s what Sudan’s 21-year civil war was all about. More than 2 million people died in that terrible religious-themed conflict between the Muslim, Arab-led north and the pagan and Christian black south. In reality, almost no one in the south bought the unity line except their charismatic (and autocratic) leader, John Garang. Garang, a favorite of the West, negotiated Sudan’s 2005 peace treaty, the Comprehensive Peace Agreement, that finally ended the war. The document was essentially written to ensure he would be elected Sudan’s first black president.

How is it that the current president of Sudan (picture to the left) isn’t black, but Barack Hussein Obama is black? I’m in the category of people who think the world “race” has some utility and maps onto real patterns of human variation, but sometimes it’s just funny. The distinction between the Arabs of Sudan and blacks of Sudan is kind of weird, because Arab is not a race, and Arabs can be of any race theoretically (there are even Arabs in Yemen’s Hadhramaut who have a lot of Malaysian ancestry because of international trade), though generally they are of the olive persuasion. Perhaps the Sudanese Arab elite wouldn’t want to be identified as black because that isn’t particularly prestigious, but they’d certainly be identified as such in other Arab countries. Anwar Sadat was the subject of some racist attitudes within Egyptian society because of his Sudanese ancestry (his mother was Nubian) and his dark skin.

Anyway, my amusement was mostly the fact that they went with this text, and, added a picture of a man who most Americans would identify as black but noted implicitly that he wasn’t black. American journalists are generally punctilious about following the rule of hyodescent when it comes to Americans, even when those individuals object to this framing, such as Tiger Woods (who is twice as Asian ancestrally as he is black). But I guess in an international context they will bend more. It reminded me of stories that Afro-Arabs were often allowed to stay at “whites only” facilities in the USA when segregation was the norm because they were foreign.

Note: Hypodescent isn’t just an American issue. There are controversies about a new biopic of Alexandre Dumas where he is played by Gérard Depardieu. Some people wanted a non-white actor cast because Dumas’ mother was mixed-race. But of course Dumas was mostly white, and he seems to basically have looked like a white guy. France of the 19th century was not the American South of the 19th century, and a drop of black blood did not make you persona non grate within white society. If you want real accuracy, perhaps cast Wentworth Miller as a young Dumas, he’s a white-looking mixed-race actor.

Image Credit: Slate & Whitehouse.gov