22 March 2011

Interesting Studies

* A new study predicts the extinction of religion in nine countries using models similar to those to predict language extinction. (See also here on language extinction: 6% of the world's languages are spoken by 94% of the world's population. The remaining 94% of languages are spoken by only 6% of the population. 133 languages are spoken by fewer than 10 people.) "The team took census data stretching back as far as a century from countries in which the census queried religious affiliation: Australia, Austria, Canada, the Czech Republic, Finland, Ireland, the Netherlands, New Zealand and Switzerland." The key constant in their model in all of the studied countries was a best fit to a value that would lead to completely secular beliefs in the long run.

Daniel M. Abrams, Haley A. Yaple, Richard J. Wiener, "A mathematical model of social group competition with application to the growth of religious non-affiliation."

The model looks at the proportion of people who are religious, the proportion of people who are non-religious, and assumes that conversion rates in each direction are a function of the proportion of the population that belongs to that group and a constant called "u" for the perceived utility of membership in that group. This probability they put in the form: "c(x^a)(u), where c and a are constants that scale time and determine the relative importance of x and u in attracting converts, respectively." Using 85 sets of long term census data they found that the best fit to "a" was 1, that c is also succeptible to global fits, and that u varies from place to place. When they solve the equations on this basis they find:

The behavior of the model can be understood analytically for a = 1, in which case we have dx/dt=cx(1-x)(2u-1): logistic growth. An analysis of the fixed points of this equation tells us that religion will disappear if its perceived utility is less than that of non-affiliation [i.e. u is greater than 0.5], regardless of how large a fraction initially adheres to a religion. However, if a is less than but close to one, a small social group can indefinitely coexist with a large social group.

The study estimated the constant "u" from census of religion data for "(a) the autonomous Aland islands region of Finland, (b) Schwyz Canton in Switzerland, (c) Vienna Province in Austria, (d) the Netherlands. . . . Relative utilities for the religiously unaffiliated populations as determined by model . . . were u = 0:63; 0:70; 0:58; 0:56."

No estimate of the key constant was made for the United States, which is far less secular than the countries studied, but has a growing non-religious population. There is also good reason to wonder if the either or model used in the study (in which religious or non-religious were the only categories) makes sense in a nation without a tradition of an established or locally dominant religion as found in most of the studied areas.

The general empirical trend in the study of American religious affiliation has been a candle burning at both ends result, with both more demanding religious faiths and secular beliefs growing at the expensive of mainline moderate religious belief. Similarly, in Latin America, the trend has been to see a growth in both Pentacostal faiths and secularism at the expensive the Roman Catholicism which is the dominant established church. In sub-Saharan Africa, the trend has been for conversion from animism to Christianity, with a minor growth factor (partially demic and partially from conversion) for Islam, while secular views have not been particularly notable as a share of the population.

Put another way, there is a lot to be said for a logistic model to explain trendlines in religious affiliation, but the model does nothing to explain what drives changes in the key constant "u" that drives these trends. By analogy, is is compable to looking at politics at an electoral level without really examining the movement politics that cause political views to change in the general population over time.

This model is a good antidote, however, to purely population genetic models that start from the assumption that children will share the faith of their parents, rather than attempting to quantify propensities to convert from one faith to another in a meaningful fashion. To some extent, by deriving empirical constants in the model from data, it glosses over these theoretical objections in a robust way. The constant "u" effectively subsumes both conversion propensities and reproduction rates. But, near the extremes, it becomes more and more important to recognize the relevance of subgroup membership, subgroup coherence, and reproduction rates, although its constant "a" can help mediate that result.

For example, in the sample "a" equals 1 model, it can't explain the persistence, and even growth, of faiths that Judaism and the Amish, in the face over overwhelming minority status for thousands of years and hundreds of years respectively. More generally, a more realistic model would assume a hetrogeneous propensity to convert which might very well have a hereditary component (due to psychological tendencies to take certain approaches to tradition and authority selected for heavily through religious endogamy when a religion is in the minority).

In more complex models, some religious populations and some personality types might be slow to convert, while others might convert more rapidly, and if the populations slow to convert also have more children and have children younger, you might end up with a bimodal outcome with a stable, fertile religious segment and a stable less fertile non-religious segment. It isn't hard to imagine the United States and Latin America evolving into this kind of equalibrium. And, while Turkey is nominally 99% Muslim, its division into different varieties of Islam arguably reflects this kind of balance.

* In a decidely participant-ethnographic investigation, New York City dezinens have discovered that godless people who get together in clubs are happier.

* A parasitic factor in mental illness may have been located:

Toxoplasma gondii infects approximately 25 percent of the human population. The protozoan parasite is noted for altering the behavior of infected hosts. . . .

"It is noteworthy that we found vasoactive intestinal peptide receptor 2 (VIPR2) was upregulated by all three Toxoplasma strains," says Xiao. VIPR2 "is linked to schizophrenia in some recent publications. Since the tropism of Toxoplasma for brain has been linked with specific behavioral changes and psychosis in humans, this finding will have some fundamental significance for understanding the correlation between Toxoplasma and psychosis."

The report based on the study by J. Xiao, L. Jones-Brando, C. C. Talbot, R. H. Yolken. "Differential Effects of Three Canonical Toxoplasma Strains on Gene Expression in Human Neuroepithelial Cells." Infection and Immunity, 2010; 79 (3): 1363 DOI: 10.1128/IAI.00947-10 suggests from a mouse model that there may be an important subclass of mental health conditions with a parasitic infectious agent as a cause or trigger.

* There may be a quick and easy vaccine cure for a complication of dust mite allergies:

Monash University researchers are working on a vaccine that could completely cure asthma brought on by house dust mite allergies. If successful, the vaccine would have the potential to cure sufferers in two to three doses. . . . Professor O'Hehir has also made significant gains in developing a vaccine for people with peanut allergies. Currently there is no specific treatment for peanut allergy with avoidance and emergency treatment of anaphylaxis with adrenaline as the only options. Allergen immunotherapy is available for selected patients with house dust mite allergy but typically injections need to be given regularly for three to five years.

I've never been diagnosed with asthma, but do have a dust mite allergy and have had subclinical asthma-like symptoms, so this is naturally of great interest to me.

* Native Americans had big influences on the environment of the Americas beyond a megafauna extinction, in the Everglades:

Tree islands are patches of relatively high and dry ground that dot the marshes of the Everglades. Typically a meter (3.3 feet) or so high, many of them are elevated enough to allow trees to grow. They provide a nesting site for alligators and a refuge for birds, panthers, and other wildlife.

Scientists have thought for many years that the so-called fixed tree islands (a larger type of tree island frequently found in the Everglades' main channel, Shark River Slough) developed on protrusions from the rocky layer of a mineral called carbonate that sits beneath the marsh. Now, new research indicates that the real trigger for island development might have been middens, or trash piles left behind from human settlements that date to about 5,000 years ago.

These middens, a mixture of bones, food discards, charcoal, and human artifacts (such as clay pots and shell tools), would have provided an elevated area, drier than the surrounding marsh, allowing trees and other vegetation to grow. Bones also leaked phosphorus, a nutrient for plants that is otherwise scarce in the Everglades.

And, in the Eastern United States where "prehistoric people decreased forest cover to reorient their settlements and intensify corn production. They also contributed to increased sedimentation in valley bottoms about 700 to 1,000 years ago, much earlier than previously thought. The findings suggest that prehistoric land use was the initial cause of increased sedimentation in the valley bottoms, and sedimentation was later amplified by wetter and stormier conditions."

* Unimpressive social science discovery of the week: Subjects in psychology experiments distinguish between real human beings and mere video recordings of human beings.

* Traits that cause organisms to disperse rapidly in space lead to selective evolution without regard to other measures of biological fitness.

* We know more about the apes of Europe and Asia tens of millions of years ago than we used to know:

Extant apes (Primates: Hominoidea) are the relics of a group that was much more diverse in the past. They originated in Africa around the Oligocene/Miocene boundary, but by the beginning of the Middle Miocene they expanded their range into Eurasia, where they experienced a far-reaching evolutionary radiation. . . Here we provide an updated chronology that incorporates recently discovered Iberian taxa and further reevaluates the age of many previously known sites on the basis of local biostratigraphic scales and magnetostratigraphic data. Our results show that identifiable Eurasian kenyapithecins (Griphopithecus and Kenyapithecus) are much younger than previously thought (ca. 14 Ma instead of 16 Ma), which casts serious doubts on the attribution of the hominoid tooth from Engelswies (16.3–16.5 Ma) to cf. Griphopithecus.

1 comment:

andrew said...

"Australia, Austria, Canada, the Czech Republic, Finland, Ireland, the Netherlands, New Zealand and Switzerland."

Is it a coincidence that all of these except Finland involve countries have substantial populations that speak Germanic languages (Switzerland and Finland are multilingual)?