This year is the bicentenary of the birth of Charles Darwin, and the 150th anniversary of the Origin of Species. Predictably, there will be a large number of commemorative events and publications. I found a useful list here. I suspect that by March we will all be heartily sick of CD, but I am still looking forward to the re-opening of Down House.

My immediate reason for posting is to draw attention to a series of programmes on BBC Radio 4 in the coming week, including four special editions of Razib's favourite 'In Our Time'. I assume that these will be available worldwide online. Incidentally, while checking the Radio 4 schedules I noticed that on Tuesday there is a documentary on the singer Nico, so it is a good week for the discerning minority who are fans of Charles Darwin and the Velvets.

This note concludes my discussion of R. A. Fisher's neglected treatment of human evolution in The Genetical Theory of Natural Selection. In Part 1, here, I pointed out that Fisher believed that human evolution was continuing rapidly in the present day. He also argued that natural selection among humans now operated mainly through differences in fertility rather than mortality. It was therefore important for Fisher to show that such differences in fertility were heritable.....


The Inheritance of Human Fertility

Chapter 9 of GTNS deals with this subject. Fisher first provides data to show that the variance in human fertility is far higher than would be expected by chance, that is, if offspring were allocated to parents by a random process (p.207-9. As previously, I will give page references to the Dover edition). Some individuals have fewer, and some more, offspring than can be expected on a chance basis. He remarks that the non-random element in human reproductive variance appears to be much higher than in most other organisms (apart from the social insects, where some individuals specialise in reproduction). Among humans differences in fertility are also more important than differences in mortality (p.213). Fisher then discusses the factors leading to such large differences in fertility, and suggests that they are mainly differences of temperament rather than physiology (p.209-13). Fisher believes these differences largely innate (p.210-11), making it plausible that they are to some extent heritable. He then considers direct evidence of the inheritance of fertility, and concludes that over 40% of the observed variance is due to heritable causes (p.217). Unfortunately, his evidence for this rests entirely on studies of the British aristocracy. Subsequent studies of wider samples have usually produced lower estimates of heritability, sometimes effectively zero. However, a recent survey of the literature by M. Murphy suggests that the correlation between fertility of parents and offspring is not negligible, and may have been increasing over time. But little is known about the extent to which this correlation is due to genetic rather than cultural factors.

Social Differences in Fertility

Chapter 10 produces evidence from several countries that under modern conditions fertility is inversely related to social class: the higher the class, the lower the fertility. His evidence is reasonably strong, so I need not elaborate on it. He also makes a number of interesting comments:

a) he disputes the common belief that the class differential in fertility is due to the earlier adoption of birth control by the higher classes, and that the differential will disappear as the use of birth control spreads (p.239). Here Fisher has been proved partly right (in Britain, at least): the differential has not disappeared, but it has narrowed with the availability of modern contraceptives, and especially the Pill. Moreover, for much of the 20th century there was a 'U-shaped' fertility pattern, with the highest and lowest social classes more fertile than the lower-middles.

b) Fisher believes that the inverse correlation of class and fertility is comparatively recent in the modern West, but that it also existed in ancient Greece and Rome (p.241).

c) the inverse correlation is 'unnatural' in the sense that it has to overcome natural obstacles. Ordinarily, we would expect the wealthier classes to be more fertile, because they could delegate much of the burden of parental care (p.242).

d) the fertility differential means that a large amount of upward social movement is needed just to maintain the proportions of different occupational groups. Fisher has some interesting discussion of the effects of this on social attitudes and values (p.243-5). But he probably overestimates the importance of differential fertility as compared with economic and technological development. There has been a huge increase in the proportion of non-manual jobs in modern economies, which cannot be explained by differential fertility.


The Social Selection of Fertility

To explain the social class fertility differential Fisher appeals to what he calls the 'social selection' of fertility (p.250-6). (He gives credit for the basic theory to the little-known eugenist J. A. Cobb.) The key point of the theory is that in modern societies social class is influenced both by natural ability and by the resources provided by parents to their offspring, such as paid education, jobs in family businesses, capital gifts and loans, influential social contacts, etc. Since the amount of resources available per child is greater when there are fewer children in the family, there is a social advantage in relative infertility. Given equal natural ability, children from small families are more likely to rise in social status (or avoid a decline) than those from large ones. The higher social classes will therefore become on average less fertile. Since marriage occurs mainly within social classes, the qualities correlated within each class (such as high abilities and low fertility in the upper classes) will become statistically and genetically linked. Fisher then proposes this as the main factor behind the decline of ruling classes and of civilisations (p.256-61). He discusses but rejects alternative explanations, and in particular Gobineau's theory that decline is due to racial mixture. Fisher points out that racial mixture increases genetic variance and therefore increases the intensity of natural selection, but whether this helps or harms the quality of the population (in 'virtue and ability') will depend on the prevailing conditions of selection. If they are unfavourable (dysgenic) racial mixture will accelerate the decline, but if they are favourable its long-term effects will be beneficial (p.257) despite possible short-term drawbacks.

Stages of Human History

Fisher argues that a negative correlation of social class and fertility will occur whenever social conditions are similar to those in modern western society; broadly, whenever society is based on 'individuals co-operating for mutual advantage in a state of law and order' (p.261). But many societies are not of this kind. Fisher particularly discusses what he calls (in a non-pejorative sense) 'barbarian' societies, such as those of the Homeric poems, where there is little central government and law, and social life is based on kinship and the institution of the blood feud. In such societies fertility is a positive social advantage, and infertility a drawback (p.261-4). The qualities recognised by the society as valuable therefore become positively correlated with fertility (p.264). Fisher considers this form of 'social selection' far more powerful in promoting 'the higher human faculties', such as aesthetic appreciation, than either individual or group selection (p.264). He then has a fascinating section on 'Heroism and the higher human faculties', in which he give a major role to sexual selection. Unlike some more recent writers, such as Geoffrey Miller, Fisher recognises that marriage choices in such a society are made not by individuals but by families: 'The prestige of the contracting parties is all-important, and while this is partly personal, it is also largely tribal' (p.266). Sexual selection therefore reinforces the advantages of such socially valued attributes as heroism, even beyond the point at which they are directly beneficial (p.266); an example of Fisher's famous 'runaway' process. Fisher himself summarises his theory as follows:

To summarize the points of anthropological importance: (i) a barbarian people organized in kindred groups and recognizing the blood feud as the principle of social cohesion, can scarcely fail to experience a selection in favour of two qualities on which the success of the kindred group principally depends (a) the public spirited, patriotic, or heroic disposition (b) fertility. (ii) The stratification of society in these two qualities implies a selective advantage of the heroic temperament beyond the optimum advantage ascribable to prudent boldness, by reason of the social advantage of fame or heroic reputation. (iii) The power of recognizing the heroic qualities, and of conscious choice in intermarriage, introduces the dual effect of sexual selection in intensifying both the qualities selected and the communal recognition and appreciation of such qualities. (iv) This selection of the popular emotional response to the heroic qualities has the important effects of (a) stabilizing the foundations of the system by strengthening the existing basis of social cohesion, (b) intensifying the selective advantage ascribable to fame or prestige, (c) increasing the selective advantage of all qualities consciously envisaged in sexual selection, (d) exaggerating the realities of natural inequality by the development of an extreme aristocratic doctrine of hereditary nobility.(p.268)

Overall, Fisher's theory of human evolution is subtle and ingenious, but often speculative. The evidence for some of his key propositions, such as the high heritability of fertility, is painfully thin. Nevertheless, Fisher's ideas are always intriguing, and even his wildest speculations are well worth reading. Indeed, although much of this part of GTNS inevitably seems dated, in some respects it still compares favourably with more recent treatments of human evolution. Along with Darwin's Descent of Man, and Westermarck's Origin and Development of the Moral Ideas, I believe it should have a place among those few 'classics' that are still capable of stimulating modern research on the subject.

One of the established cool examples of convergent evolution (which for my purposes here I'll define loosely here as the evolution of different populations to the same phenotype via different mutations) has been the repeated loss of pigmentation (and eyes) in fish that have adapted to life in light-poor, nutrient-poor caves. In 2006, a group reported that albinism (panel J in the picture) in several of these caves was due to mutations in OCA2 (a SNP in a regulatory region of this gene also causes blue eyes in humans).

Not all cavefish however, are fully albino--in some populations, there also exists a "brown" phenotype (panel "G" in the picture) with reduced pigmentation. In a new paper, the gene underlying this phenotype is shown to be MC1R (this gene, of course influences pigmentation in all sorts of species), and, similarly to OCA2, two different mutations have arisen in different populations.

One might imagine that light pigmentation in cavefish could just be due to simple drift--a random mutation that knocks out pigmentation is no longer selected against in a place where there's little light, and so could drift up to high frequency. But the fact that this phenotype has arisen so many times, and reached high frequency in the presumably short time period that these fish populations have been isolated (I say presumably short because I can't find any numbers on this, but the different populations can interbreed freely) suggests a role for strong positive selection for this phenotype in adaptation to the cave environment.

Labels: Evolution, Genetics

Everyone & their mother is emailing me about Jonathan Haidt's new commentary in Edge, FASTER EVOLUTION MEANS MORE ETHNIC DIFFERENCES:

I believe that the "Bell Curve" wars of the 1990s, over race differences in intelligence, will seem genteel and short-lived compared to the coming arguments over ethnic differences in moralized traits. I predict that this "war" will break out between 2012 and 2017.

There are reasons to hope that we'll ultimately reach a consensus that does not aid and abet racism. I expect that dozens or hundreds of ethnic differences will be found, so that any group - like any person - can be said to have many strengths and a few weaknesses, all of which are context-dependent. Furthermore, these cross-group differences are likely to be small when compared to the enormous variation within ethnic groups and the enormous and obvious effects of cultural learning. But whatever consensus we ultimately reach, the ways in which we now think about genes, groups, evolution and ethnicity will be radically changed by the unstoppable progress of the human genome project.

Yes, psychopathy might have adaptive "strengths" in a frequency dependent context, but I don't think that's what Haidt meant! One difference with the IQ wars when it comes to personality is that it seems every single dopamine receptor has already been implicated in behavior genetic variation, while we're still a long way from IQ loci results which have been reproduced, though one might double-check on the details of the statistical analyses on suggestive findings from behavior genetics. In any case, since the heritability of behavior in economic games has already been established, it would be interesting if GWAs found some loci which tracked the variation. My own hunch is that personality variation is less continuous than IQ (characterized by a few morphs hanging around fitness peaks), with an underlying architecture of larger effect QTLs. Perhaps altruism is just way simpler to modulate than general intelligence?

Labels: human biodiversity

Spontaneous Facial Expressions of Emotion of Congenitally and Noncongenitally Blind Individuals:

The study of the spontaneous expressions of blind individuals offers a unique opportunity to understand basic processes concerning the emergence and source of facial expressions of emotion. In this study, the authors compared the expressions of congenitally and noncongenitally blind athletes in the 2004 Paralympic Games with each other and with those produced by sighted athletes in the 2004 Olympic Games. The authors also examined how expressions change from 1 context to another. There were no differences between congenitally blind, noncongenitally blind, and sighted athletes, either on the level of individual facial actions or in facial emotion configurations. Blind athletes did produce more overall facial activity, but these were isolated to head and eye movements. The blind athletes' expressions differentiated whether they had won or lost a medal match at 3 different points in time, and there were no cultural differences in expression. These findings provide compelling evidence that the production of spontaneous facial expressions of emotion is not dependent on observational learning but simultaneously demonstrates a learned component to the social management of expressions, even among blind individuals.

Also see ScienceDaily.

Labels: Psychology

Lots of charts.

Samuel Huntington died yesterday. Though famous for his Clash of Civilizations thesis, more recently he argued for an emphasis on the reality that this (the United States) is an Anglo-Protestant country. But I think that this assertion needs to clarified to a finer grained scale. In Albion's Seed: Four British Folkways in America, the author makes the claim that the culture of the United States is a synthesis of four strands of colonial settlers; New England Puritans, the Lowland Southerners (e.g., Tidewater Planters), the Highland Southerners (i.e., the Scots-Irish of Appalachia) and the polyglot peoples of the Mid-Atlantic (e.g., Quakers of Philadelphia, Dutch Patroons of New York and Swedes of Delaware, etc.). After reading quite a bit of American history, especially the period between 1600 and 1850, I think that over the long haul the concrete political and social realities of America owe much more to New England than the other regions.  After I came to this conclusion (which I will flesh in more detail later), I couldn't help but note that today New England isn't included in the "Real America."

Labels: culture

Massimo Pigliucci has a post up, Economics learns a thing or two from evolutionary biology. There are many points within the post which I would agree or disagree with, but, I get the sense that the current economic morass is precipitating these sorts of criticisms of "economics." I'm not one to disagree on the importance of behavioral economics, and I believe a serious engagement with the reality that rationality is bounded will only benefit the human sciences. That being said, it seems to me that the current problems are not ones of economics or the economics profession as much as the particularities of the finance profession in terms of its incentive structure. By analogy, imagine blaming zoologists and botanists for the actions of agribusiness (e.g., excessive utilization of antibiotics so as to maximize short term firm productivity at cost to a risk of a high negative externality). Rather than suggest that economics needs to learn from the life sciences (I think this is happening), I believe that you need to look to public choice theory and other extant frameworks available off the shelf.

Labels: Economics

THE MATH SEX GAP REVISITED: A THEORY OF EVERYONE by La Griffe, via Half Sigma.

Labels: human biodiversity

This is a pretty thorough review of biology and evolution of lactase persistence. It's interesting that the precise genetic mechanism underlying the phenotype remains unknown-this seems like a potentially very interesting model phenotype for people interested in the temporal and spatial regulation of gene expression.

Labels: Genetics

Check out Mark Wethman's new quant blog, Congenial Times. It's been around for only a couple of weeks but in that time he's posted a lot of interesting data/analysis on topics ranging from international politics to human biodiversity. His most recent post is on racial differences in educational attainment in Sweden.

The most interesting article to me has been the one on Amish IQ scores. He found data which showed the Amish to have above average reasoning and quantitative analysis skills.* Data like this is essential for anyone trying to understand the Flynn Effect or between-population differences on IQ scores.

*They scored lower on language tests, but according to Jason Malloy this was solely due to the tests not being in their native Pennsylvania Dutch.