hajnal

new theme song for the blog! (not that there was an old one….) h/t professor zaius! (^_^)

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dawkins on race

and, incidently, sex. from The Ancestor’s Tale — h/t to the person who linked to this on twitter the other evening. i forgot who it was! (*^_^*) (sorry!) [pgs. 406-408 — links added by me]:

“It is genuinely true that, if you measure the total variation in the human species and then partition it into a between-race component and a within-race component, the between-race component is a very small fraction of the total. Most of the variation among humans can be found within races as well as between them. Only a small admixture of extra variation distinguishes races from each other. That is all correct. What is not correct is the inference that race is therefore a meaningless concept. This point has been clearly made by the distinguished Cambridge geneticist A. W. F. Edwards in a recent paper called ‘Human genetic diversity: Lewontin’s fallacy’. R. C. Lewontin is an equally distinguished Cambridge (Mass.) geneticist, known for the strength of his political convictions and his weakness for dragging them into science at every possible opportunity. Lewontin’s view of race has become near-universal orthodoxy in scientific circles. He wrote, in a famous paper of 1972:

“‘It is clear that our perception of relatively large differences between human races and subgroups, as compared to the variation within these groups, is indeed a biased perception and that, based on randomly chosen genetic differences, human races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals.’

“This is, of course, exactly the point I accepted above, not surprisingly since what I wrote was largely based on Lewontin. But see how Lewontin goes on:

“‘Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.’

“We can all happily aggree that human racial classification is of no social value and is positively destructive of social and human relations. That is one reason why I object to ticking boxes in forms and why I object to positive discrimination in job selection. But that doesn’t mean that race is of ‘virutally no genetic or taxonomic significance’. This is Edwards’s point, and he reasons as follows. However small the racial partition of the total variation may be, if such racial characteristics as there are are highly correlated with other racial characteristics, they are by definition informative, and therefore of taxonomic significance.

“Informative mean something quite precise. An informative statement is one that tells you something you didn’t know before. The information content of a statement is measured as reduction in prior uncertainly. Reduction in prior uncertainty, in turn, is measured as a change in probabilities…. If I tell you Evelyn is male, you immediately know a whole lot of things about him. Your prior uncertainty about the shape of his genitals is reduced (though not obliterated). You now know facts you didn’t know before about his chromosomes, his hormones and other aspects of his biochemistry, and there is a quantitative reduction in your prior uncertainty about the depth of his voice, and the distribution of his facial hair and of his body fat and musculature….

“Now to the question of race. What if I tell you Suzy is Chinese, how much is your prior uncertainty reduced? You now are pretty certain that her hair is straight and black (or was black), that her eyes have an epicanthic fold, and one or two other things about her. If I tell you Colin is ‘black’ this does not, as we have seen, tell you he is black. [he might be mixed race.-h.chick] Nevertheless, it is clearly not uninformative. The high inter-observer correlation suggests that there is a constellation of characteristics that most people recognise, such that the statement ‘Colin is black’ really does reduce prior uncertaintly about Colin. It works the other way around to some extent. If I tell you Carl is an Olympic sprinting champion, your prior uncertainty about his ‘race’ is, as a matter of statistical fact, reduced. Indeed, you can have a fairly confident bet that he is ‘black’.”

of course, don’t forget: there’s more to human biodiversity than just racial differences! see: most of this blog.

see also: Human Genetic Diversity: Lewontin’s Fallacy @wikipedia.

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“genes for altruism”

in Genes underlying altruism published in october of last year, three biologists/researchers think through what “genes for altruism” ought to look like and how we will recognize them (“we” meaning teh scientists!):

(i) Genes underlying altruism should satisfy Hamilton’s rule of rb > c, where r is relatedness of actor to recipient, b is benefits to the recipient and c is costs to the actor. Altruism exists, and to the extent that this type of behaviour has evolved, we expect genetic variation to underlie it. In this sense, there must be genes ‘for’ altruism (genes showing allelic variation that is statistically associated with variation in altruistic behaviour) that are potentially detectable….

(ii) Genes underlying altruism should be environmentally sensitive. If genes for altruism are to evolve, then at least some carriers must reproduce. This inference implies that genes underlying altruism should be conditionally expressed as a function of their social environment….

(iii) Genes underlying altruism should increase in number and complexity with social-behavioural sophistication….

(iv) Genes underlying altruism should coevolve with, or depend on, the previous evolution of genes for kin recognition….

(v) Genes for altruism may reside in regions of low recombination, exhibit co-expression and show modular genetic architecture….

(vi) Genes underlying altruism should be at least partially additive. The evolution of altruism requires heritable variation, and we therefore expect genes for this and other evolved social traits to have significant additive effects that are responsive to kin-mediated selection….

(vii) Genes underlying altruism should exhibit strong pleiotropy. Pleiotropy (multiple phenotypic effects of alleles) should be fundamental to the evolution of altruism, given that it involves combinations of costs and benefits that may be simultaneously physiological, morphological, reproductive and behavioural….

the authors offer some candidate “genes for altruism” (this is a truncated version of their table. i’ve only included the ones for humans here — they also suggested some for eusocial insects):

i think teh scientists should also look for some genes related to violence — particularly tempermental, hotheaded sorts of violence — the kind that raises the testosterone levels of scots-irish, but not yankee, folks when they’re insulted. those types of fly off the handle behaviors, i think, are often altruistic in nature, since the hotheaded individual can be more willing to sacrifice himself in a fight or in battle for his kin.

also, i guess that “genes for altruism” ought to be found in differing frequencies — even variations — in different human populations, especially long-term inbred versus long-term outbred ones.

(^_^)

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cousin marriage in sub-saharan africa

whenever i’m kinda tired and slightly braindead, i usually start trawling the streets google books or online journals for any info/data on mating patterns in human populations. (unless i rewatch star wars for the umpteenth millionth time, obviously.) it’s my own, personal form of trainspotting just with less trains. and more mating patterns.

so i thought i’d share with you what i’ve got to date for sub-saharan (ss) african populations. this is faaar from being a complete list, nor is it systematic in any way. it’s just the stuff that i’ve happened to come across so far, so don’t read anything into the list like “overall there seems to be more inbreeding or outbreeding” or whatever.

first of all, there are a LOT of ss african populations! thousands. so, you know, it’ll take some time to get info on them all! here’s a map of the broad ethnolinguistic groups of africa that i’ve stolen from wikipedia — remember that there are hundreds if not thousands of subgroups within these broad groups:

needless to say, with such a wide variety of peoples, there is also a wide variety of mating patterns in ss africa. some populations avoid cousin marriage altogether. we’ve already seen this with the bamileke of cameroon and the igbo of nigeria. also the turkana of kenya and quite possibly the amhara of ethiopia (not 100% sure about them — need to double-check). a notable group which apparently avoids cousin marriage is the zulu. but plenty of other ss africa groups do practice cousin marriage like, as you’ll see in the table below, the kongo and luba in the democratic republic of congo, the ashanti in ghana, the sotho-tswana in south africa, and the kpelle of liberia. (fun fact that’s stuck in my brain for some reason — some of oprah’s ancestors were probably kpelle.)

the most common form of cousin marriage in ss africa is mother’s brother’s daughter (mbd) marriage which isn’t too surprising since that is the most common form of cousin marriage in the world. there’s an interesting twist to it in ss africa, though, thanks to all of the polygamy which is also very common in ss african societies. here from robin fox [pg. 195]:

“This latter form of marriage [mother’s brother’s daughter] is common in Africa and in patrilineal societies generally. Often, in Africa, it goes along with marriage to the wife’s brother’s daughter, as shown in diagram 4.2. A man either marries his wife’s brother’s daughter or passes the privilege on to his son (at least this is one way of looking at it). In many societies it is simply a straightforward privilege to marry the mother’s brother’s daughter.”

so, yeah, in case you were wondering, that would make the kids of these two wives (wife number one/aunt and wife number two/niece) both half-siblings and first cousins once-removed. and the children of wife number one are the first cousins once-removed to their father (and mother). and the children of wife number two are second cousins to their father. i think. i’ll let you think about it for a while. (~_^)

there is some father’s brother’s daughter (fbd) marriage (the type favored by the arabs) in some areas of ss africa — most notably amongst the hausa and fulani in northern nigeria, and the songhai and soninke in mali — but these are all muslim groups who i would guess picked up fbd marriage from the arabs/north african groups that introduced islam to them. youssef courbage and emmanuel todd think otherwise [pg. 43]:

“So-called Arab marriage, accepting union with any first cousin, but preferably with the father’s brother’s daughter, is not characteristic of sub-Saharan Africa. It is widely practiced only by the Fulani, nomadic herders of the northern fringe, immediately south of the desert, at a level so much higher than the Arab norm that it probably had an independent origin. It is also characteristic of some sedentary groups in the same area (Soninke in Senegal, Mali, and Mauritania; Songhai in Mali; Hausa in northern Nigeria). In West Africa, marriage is usually either exogamous or characterized by a preference for cross-cousin marriage, that is, between the children of a brother and a sister, a practice that has nothing to do with Islam.”

i don’t know if that statement about the fulani practicing a greater amount of fbd marriage than the arabs is correct or not. i shall have to try and find out. (here might be a good place to start.) i think it’s more likely that, being that the fulani have obviously been in contact with the arab/muslim world for quite a long time, they picked up the practice in that way. the afghanis and pakistanis also practice quite a lot of fbd marriage even though they’re at the edge of the “arabized” world, albeit at the other end of it, so i doubt that distance from arabia matters much here. it’s the contact with the greater arab world that counts.

two ss african groups that do seem to have adopted fbd marriage independently are the sotho-tswana and venda of south africa. need to learn more about those two groups. (note that the fbd marriage recorded in the table for the tutsi in rwanda refers only to some of the elites, not the general population.)

additionally, as in christian europe (especially medieval europe), some ss african groups prohibit marriage between in-laws — which is interesting. one example are the yao of malawi. they, however, happen to have a preference for cross-cousin marriage.

again, the other mating practice that is very common in ss africa is polygamy. i’ve said a few times here on the blog that you’d think that that would narrow the gene pool/relatedness between individuals in a group just as cousin marriage does. it might not always, though, because polygamy is not one thing either (can nothing ever be easy and straightforward?! (~_^) ). the lozi of zambia, for instance, apparently practice (or did traditionally) a sort of rapid serial polygamy, with wives being shuffled rather quickly on to the next husband, so that wouldn’t really narrow the genetic relatedness in the population at all, afaics. quite the opposite really. on the other hand, some groups practice sororal polygamy with the men making sure to marry sets of sisters, so that would narrow the relatedness in the group more so than a more basic form of polygamy in which men married women more randomly. the conclusion wrt polygamy, i think, is that each group will have to be evaluated on an individual basis. (*sigh*)

problem number one: for my purposes, since i’m interested in evolution and the selection of behavioral traits, i need to know how long populations have been inbreeding or outbreeding for, since natural selection does take some amount of time (but not necessarily millions of years). that’s difficult to work out for ss africans (and most of the world for that matter) without historic records or reams of genetic data which we haven’t got yet. it might be possible to reconstruct some of the history of mating patterns for some of the groups in ss africa from colonial accounts, especially those of missionaries who also acted as early ethnographers in many ways. we shall see. it would certainly be interesting to know for how long some of these groups have been inbreeding or outbreeding. as we’ve already seen, for instance, wikipedia claims that the igbo had a “quasi-republican” form of government in the 1400s with some sort of one-man-one-vote system. that’s not a system you find in heavily inbreeding societies — at least none that i can think of. what if it’s connected to the igbo outbreeding? dunno. Further Research is Required^TM — and most likely it’ll have to be genetic.

problem number two: don’t have a whole lot of info on the rates of cousin marriage (or not) for most of these populations either. that’s also an extremely important detail to know. here are the few groups that i do have some numbers for:

– the fulani of burkina-faso: 65.8% first and second cousin marriage rate
– the fulani, mandinka, and wolof in gambia: 65% of first marriages of men are to a cousin – that’s an average of the three populations, and i don’t have a breakdown for each group
– the fouta-jallon (taramabli-dionfo) of guinea: 25.9% cousin marriage rate
– the yoruba of oka akoko in nigeria: 51.2% cousin marriage rate
– the lobedu (sotho) of south africa: 30% cousin marriage rate

so, there’s a variety in the rates, too. again, not surprising.

i think that’s it by way of the intro, so without further ado, here is my table. oh, the populations highlighted in yellow are those which include more than ten million people. and many of these groups spill over into other countries, of course, apart from the ones in which i’ve listed them [click on table for LARGER view – should open in new tab/window]:

i think that’s it for now! stay tuned. (^_^)

sources:
– A Companion to Ethics
– Consang.net – Table 1 – Consanguinity in Africa [pdf]
– Contingent Lives: Fertility, Time, and Aging in West Africa
– A Convergence of Civilizations: The Transformation of Muslim Societies Around The World
– Culture and Customs of South Africa
– Ethnic Groups of Africa and the Middle East: An Encyclopedia
– The Family Estate in Africa: Studies in the Role of Property in Family Structure and Lineage Continuity
– Joking, Affinity and the Exchange of Ritual Services Among the Kiga of Northern Rwanda: An Essay on Joking Relationship Theory
– The Making of the Pentecostal Melodrama: Religion, Media and Gender in Kinshasa
– Man in Africa
– Milk, Honey, and Money: Changing Concepts in Rwandan Healing
– Nomads who Cultivate Beauty: Wodaabe Dances and Visual Arts in Niger
– The Problem of Context
– Reproduction and Social Organization in Sub-Saharan Africa
– Seven Tribes of British Central Africa
– Slavery in Africa: Historical and Anthropological Perspectives
– The Social Basis of Health and Healing in Africa
– Structure and Sentiment: A Test Case for Social Anthropology
– Women and Marriage in Kpelle Society
– Women of Tropical Africa

previously: the bamileke of cameroon and fulani, hausa, igbo, and yoruba mating patterns and the turkana: mating patterns, family types, and social structures and ethiopia notes and
flatlanders vs. mountaineers revisited

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inbreeding, digit ratio, and altruism

in his post A pathway to pro-social behavior, peter frost references this article Second-to-Fourth Digit Ratio Has a Non-Monotonic Impact on Altruism in which the authors say:

“We find an inverted U-shaped relation for left and right hands, which is very consistent for men and less systematic for women. Subjects with both high and low digit ratios give less than individuals with intermediate digit ratios.“

the subjects were w.e.i.r.d.-ish, btw — university students from granada, spain.

peter comments:

“From one population to the next, digit ratios tend to cluster around different means, perhaps because altruism has been favored or disfavored to different degrees.”

i’m not familiar with those differences (will have to investigate), but i did post this from turkey in a recent linkfest:

“Inbreeding is associated with lower 2D:4D digit ratio”

“We compared the 2D:4D ratios of 122 male and 108 female consanguineous (children of first cousin marriages) high school and university students to those of 142 male and 122 females controls. Across hands and sex, consanguineous parentage was consistently associated with lower, more masculine-typical, digit ratios. Digit ratios were 1.3–1.9 times more variable among the consanguineous group than the control group. While socio-economic status cannot explain the effects seen in our data, we found that lower, more masculinized, digit ratios were associated with lower family income.”

inbreeding leads to…whatever genotypic/phenotypic package that results in lower 2d:4d digit ratios *and* lower rates of altruistic behaviors? dunno. Further Research is Required^TM.

ftr — i come from a population that has been inbreeding up until fairly recently, and i’ve got a low 2d:4d digit ratio. uh oh.

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fulani, hausa, igbo, and yoruba mating patterns

the war nerd says of some of the populations in nigeria:

“Nigeria’s three parts were simply nailed together by the British for their Imperial convenience: The North is a Muslim theocracy dominated by the Hausa and Fulani; the West, where the Yoruba kings (Oba) ruled city-states; and the East, where the Igbo operated on something a lot like ancient Greek assemblies, with every freeborn man entitled to a voice.”

hmmmm. doesn’t that sound interesting! more…

“The Yoruba were the first to meet the whites and take up Western education. They dealt with the British town by town; to the Yoruba, your town was more important than the broader ethnic identity. The Igbo came late to British rule but took to education very quickly. The Igbo get called ‘the Jews of Africa’ because they’re good at book-learning and business.

“And then there were the Northerners, the Hausa-dominated Muslims of the dry inland territory. In a way, you wouldn’t be far off thinking of the great Nigerian divide in California terms: the coasts vs. the hot inland redneck zone. The North, in Nigerian terms, is usually called ‘Hausa,’ or ‘Hausa-Fulani,’ but it includes the Kanuri of the Northeast, who are the most remote from the coast and the fiercest opponents of anything coastal, Christian, or modern. These were all war-forged Sahel caliphates, with no tradition of local loyalties like the Yoruba, or egalitarianism like the Igbo. They had the traditional Sahel-Muslim organization, top-down all the way: Sultan gives orders to Omda, Omda gives orders to Sheikh, Sheikh gives orders to commoners. And commoners obey.”

so we’ve got clannish/tribal northerners — the fulani and the hausa. and then we have the city-state yoruba and the “egalitarian” igbo.

i’d just like to point out that:

– the fulani prefer first or second cousin marriage and specifically father’s brother’s daughter (fbd) marriage. they’re pastoralists. there are good chances i think that, like other groups elsewhere, the fulani adopted the fbd marriage of the arabs when they converted to islam (starting in the 1400s?), but perhaps they simply practice fbd marriage because they’re pastoralists.

– the hausa also prefer cousin marriage, but it seems cross-cousin marriage, so we’re talking father’s sister’s daughter (fzd) or mother’s brother’s daughter (mbd) marriage. they are also largely muslim, but don’t seem to have adopted the fbd marriage of the arabs like their neighbors the fulani. islam has been present in hausa lands since the 1200s, but it wasn’t until the 1800s that it had fully penetrated the population.

– cousin marriage doesn’t seem to be very prevalant amongst the yoruba [pg. 74] — definitely they don’t seem to *prefer* any particular form of cousin marriage [pg. 102]. some subgroups of yoruba do have very high cousin marriage rates — the people in the town of oka akoko were found to have a consanguinity rate of 51% which included uncle-niece marriages [pg. 4]. notably, oka akoko is in a mountainous region. another case of mountaineers marrying closely? dunno. Further Research is Required^TM!

– the igbo avoid cousin marriage altogether. no form of cousin marriage is permitted. no idea how far back this goes, but it would sure be interesting to know. if wikipedia is to be believed, the igbo had a “quasi-republican” form of government in the 1400s (see also here). wouldn’t it be cool if that system was connected to mating patterns?! dunno though. we shall have to wait and see if any further info presents itself.

oh, and btw — polygamy is present in all of these groups — and probably has been for a long, long time.

perhaps there’s something in all this, perhaps not, but these groups do seem to fit the usual pattern — closer mating patterns=more closed societies, broader mating patters=more open societies. dunno. just sayin’. Further Research is Required^TM!

previously: the bamileke of cameroon

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