Read More

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.

Well, sort of. I’m reading Henry Kamen’s Empire: How Spain Became a World Power. Kamen is no Charles C. Mann, his story isn’t 1491. For him the conquest of the Aztecs and Incas were haphazard affairs driven more by entrepreneurial intent than religious zeal or Spanish patriotism; his lens is that of social and economic history. Kamen’s goal is to debunk those who would attempt to assert that the colonization of the New World was part of some grand imperial plan. It obviously wasn’t, the personal correspondence of Charles V, the titular sovereign under whom the original New World conquests occurred, show a far greater attention and focus upon the geopolitical circumstances of Central Europe.¹ Nevertheless, Kamen can not ignore the large role that the immunological parameter played in aiding the Spanish conquest. More accurately, Spain did not conquer the New World, the societies of the New World collapsed and the Spaniards took over in the vacuum. I couldn’t but help note that Kamen points out that the Inca redoubt at Vilcabamba, which remained an independent locus of indigenous political power for decades after the initial Spanish victories, was being wracked by pestilence as the final defeat loomed. Obviously if you are going to engage in a guerilla rearguard action it is tough going when your demographic base is being wiped out from under you. It seems that a good conservative rule of thumb is that 9/10^th of the indigenous American population in any given region was struck down within a generation of contact.² Luckily for the peoples of the Andes, they have their own biological adaptations to high altitudes which the Spaniards did not. This meant they were better suited to eventually bounce back as outsiders had a harder time settling their lands.

Read More

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.

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.

I’m 5 feet 8 inches tall. 1.73 meters. In the United States that’s somewhat on the short side, most of the charts suggest I’m around the 30th percentile for white men. Of course, I’m not white. In any case, though I’m on the short side for the typical American male, I’m a giant in my family. My father is 5 feet 4 inches. My mother is around 5 feet now. They’re possibly shorter than they were due to age, but they would have been short in the United States no matter what. As I was growing up, and surpassed my parents in my mid-teens, I assumed that their relative lack of height was a function of childhood nutritional deprivation. After all, they were born in Bangladesh!
If I had thought it through that was probably a pretty stupid reason for assuming they were short; my parents were from affluent families. Affluent enough that older family members were comfortably plump. Additionally, as Muslims they had no food taboos aside from pork, and milk and meat were widely consumed (though fish was of course a primary protein source). Though a significant proportion of the population in Bangladesh, what was East Bengal, is malnourished, no one in my family fell into that category. But this is all post facto, there’s a very specific reason I rejected my prior assumptions. I have three siblings and their heights are basically in the range of my parents (correct for sex, etc.). I’m the odd one out, not my parents. I have some “tall” uncles on both sides of my family, which in Bangladesh means around my height. My paternal grandfather was also relatively tall, reputedly above 5 feet 10 inches, while my maternal grandmother was tall for a woman in her youth. When I visited my family in 2004 one of my cousins was taller than me, around 5 feet 10 inches or so. He was the only one, there were a few who were around my height, but most were shorter. No one in my family is on the edge in terms of nutrition, though not approaching American obesity levels plumpness is not unknown even among young adults. Though we’re not plutocrats on the whole, many of my cousins have professional jobs, accountants at NGOs or systems administrators at universities and what not. Nevertheless, among them I am a giant, and my brother at 5 feet 4 inches is typical.

Read More

…yes, true. On a typical single locus (on some loci, such as SLC24A5, most of the variation is between groups). But that doesn’t mean that you can’t use genetics to differentiate population clusters. Here are 938 individuals (the points) from 51 world populations (the color of the points) displayed on a figure with the two largest principle components of the variation.

From Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation. Also see Lewontin’s Fallacy.

A new paper came out in Science this week, Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation, that’s getting some media play. The second-to-last author is L. L. Cavalli-Sforza, and the general combination of means and ends on display in The History and Geography of Human Genes, is all over it. From the introduction:

We first studied genetic ancestry of each individual without using his/her population identity. This analysis considers each person’s genome as having originated from K ancestral but unobserved populations whose contributions are described by K coefficients that sum to 1 foreach individual. To increase computational efficiency, we developed new software, frappe, thatimplements a maximum likelihood method (13)to analyze all 642,690 autosomal SNPs in 938 unrelated and successfully genotyped HGDPCEPH individuals…Figure 1A shows theresults for K= 7; those for K= 2 through 6 are in fig. S1. At K= 5, the 938 individuals segregate into five continental groups, similar to those reported in a microsatellite-based study of the same panel…At K= 6, the new component accountsfor a major portion of ancestry for individuals from South/Central Asia, separating this regionfrom the Middle East and Europe…K= 7, the new component occurs at highest proportions inthe Middle Eastern populations, separating them from European populations. In many populations, ancestry is derived predominantly from one of the inferred components, whereas in others, especially those in the Middle East and South/Central Asia, there are multiple sources of ancestry….

All good. Do note that the South Asian populations in the HGDP set are all from the northwest edge of the subcontinent, so the separation between the South Asians as an outgroup to the Middle Eastern & European branches of the broad West Eurasian cluster is going to be understated in these studies. In any case, I was interested in some details of the the first figure, so I reedited it a bit for clarity:

Read More

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 with
in 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.

In my post below, Pentecostals are stupid? Unitarians are smart?, I derived some conclusions from data which suggests that different religious groups in the United States have different IQs and/or academic aptitudes. The data are not particularly surprising, as some noted the class biases of American Protestantism have long been observed, and class usually has some correlation with education and performance on intelligence tests. That being said, one must be careful about extrapolating from one nation to others. Darwin Catholic stated:

For comparison, I seem to recall reading that Christianity correlates highly with educational and professional success in some Asian countries (Japan was the one I was reading about). In that case, as with Unitarians in the US, it would again be a case of a self selected group: only people who had actively searched out a religion different from that they were born into.

Read More