The demon within

Candida albicans. Some strains have adapted to sexual transmission. Have they gone so far as to manipulate host behavior?

Vulvovaginal candidiasis (VVC), commonly known as vaginal yeast infection, affects 70-75% of sexually active women at least once and 5-8% recurrently (Li et al., 2008). It is usually caused by Candida albicans, a single-celled fungus that reproduces asexually.

Although C. albicans can colonize many body sites, some strains have specifically adapted to the vagina. This evolutionary trajectory seems to have gone through three levels of adaptation:

Adaptation to vaginal environments

Vaginally adapted strains are a small subset of C. albicans. In China, two strains account for almost 60% of all VVC cases, yet neither is present at extragenital sites (Li et al., 2008). In the United States, C. albicans strains are much more diverse in the male partners of women without VVC than in the vaginas of women with or without VVC (Schmid et al., 1993).

Adaptation to sexual transmission

These vaginal strains seem to have also adapted to sexual transmission, specifically female-to-male transmission. Once VVC develops, they can spread to the host’s male partner by colonizing his glans penis via vaginal intercourse (Li et al., 2008) or his oral cavity via cunnilingus (Schmid et al., 1995). Vagina-to-vagina transmission has also been attested in lesbian couples (Bailey et al., 2008).

There is evidence of genetic changes for sexual transmissibility. Vaginal strains adhere better to saliva-coated surfaces than do other strains (Schmid et al., 1995). In the male partner, they tend to displace non-vaginal strains of C. albicans (Schmid et al., 1993).

Adaptation to certain sexual behaviors

Although a relationship clearly exists between sexual behavior and VVC, it is not a simple one of cause and effect. This is the conclusion of two research teams, Hellberg et al. (1995) and Reed et al. (2003), who sought to identify those aspects of sexual behavior that correlate with VVC.

Hellberg et al. (1995) found no significant association between VVC and the main indicators of vaginal sexual activity: (1) frequency of vaginal sex; (2) history of multiple sexual partners (more than 10 lifetime partners); and (3) sex with more than one partner during the last six months.

There were, however, significant associations with (1) early age of first intercourse, (2) casual sex with previous unknown partners in the past month, (3) vaginal sex during menstruation, (4) oral sex (fellatio), and (5) receptive anal sex.

Reed et al. (2003) reported similar findings. VVC was not significantly associated with frequency of vaginal sex, lifetime number of partners, and duration of current relationship. But there were significant associations with cunnilingus in the past month and masturbation in the past month. Unlike Hellberg et al. (1995), there were no significant associations with early age of first intercourse or frequency of receptive anal sex.

Reed et al. (2003) also found two risk factors in the male partner: early age of first intercourse and masturbation in the past month. There were no significant associations with his marital status, lifetime number of partners, previous partners with VVC, personal history of yeast infections, or reported fellatio or cunnilingus in the past month.

This is all rather puzzling. Occurrence of VVC was related not to vaginal sex but rather to non-vaginal sex, i.e., fellatio, cunnilingus, and masturbation. Even more puzzling, Reed et al. (2003) failed to find any association between VVC and the presence of C. albicans in the male partner, including his oral cavity. The authors concluded that the relationship between VVC and sexual behavior is not primarily one of sexual transmission:

If the association between orogenital contact and recurrent Candida vulvovaginitis is not mediated by transmission of the organism, how might increased risk be conferred? Previous study of the immunopathogenesis of recurrent Candida vulvovaginitis suggests that a delicate equilibrium exists among C. albicans, vaginal bacterial flora, and vaginal defense mechanisms, and that changes in the host environment promote the transformation of C. albicans from a saprophytic to a pathogenic existence. We suggest that the effects of genital washing with saliva—from either the male or the female—might upset this balance […] (Reed et al., 2003)

But how would this vaginal equilibrium be upset by the woman fellating her male partner? And how would it be upset by her male partner masturbating—alone and by himself?

Manipulation of host behavior?

To make sense of all this, we should perhaps reverse the direction of causality. Perhaps some vaginal strains of C. albicans have reached a third level of adaptation, i.e., manipulation of host behavior to increase opportunities for sexual transmission. Perhaps they somehow weaken the host’s sexual inhibitions and incite her to maximize contact between her vaginal fluids and colonizable sites on her partner’s body.

Does this sound like science fiction? Keep in mind that parasites manipulate host behavior in many non-human animals, and some of these parasites are likewise fungi (see here). Moreover, C. albicans has evolved the ability to cross the blood-brain barrier and colonize sites in the human brain (Jong et al., 2001). According to an autopsy of macaque brains, this microbe can recognize different kinds of neural tissue:

An ex vivo adhesion assay was used to examine adhesion of Candida albicans yeast cells to brain tissue of the primate Macaca mulata. Tissues from frontal lobes and striatum (caudate, putamen, and portions of the globus pallidus) were used in the assay. Yeast cells adhered to gray matter at about six times the level of adhesion to white matter. The fungus was able to bind to different cell types within the cortex, basal ganglia, and white matter. (Denaro et al., 1995)

One can imagine a multi-stage process of development:

1. “Behavior-modifying” C. albicans colonizes the vagina as a commensal organism with low virulence and no VVC. The ensuing period of latency might last a long time.

2. Meanwhile, the microbe spreads to other sites within the host’s body, including certain areas of the brain that influence sexual behavior.

3. Once this secondary colonization is complete, the area of primary colonization enters a highly infectious stage, i.e., VVC. The microbe is now ready to spread to her sexual partner.

And how will it influence her partner’s behavior? We cannot find the answer by studying his behavior before and during VVC—as in current studies. We must examine his subsequent behavior, i.e., once this strain of C. albicans has spread to his body and replaced other strains. Are there any behavioral changes?

But, then, what sort of changes should we expect?

(to be cont’d)

References

Bailey, J.V., R. Benato, C. Owen, and J. Kavanagh. (2008). Vulvovaginal candidiasis in women who have sex with women, Sexually Transmitted Diseases, 35, 533–536

Brainwashed by a parasite, Neurophilosophy, August 9, 2007
http://scienceblogs.com/neurophilosophy/2007/08/brainwashed_by_a_parasite.php

Denaro, F.J., J.L. Lopez-Ribot, and W.L. Chaffin. (1995). Adhesion of Candida albicans to brain tissue of Macaca mulata in an ex vivo assay, Infection and Immunity, 63, 3438-3441

Hellberg, D., B. Zdolsek, S. Nilsson, and P-A. Mårdh. (1995). Sexual behavior of women with repeated episodes of vulvovaginal Candidiasis, European Journal of Epidemiology, 1, 575-579, 1995

Jong, A.Y., M.F. Stins, S-H. Huang, S.H.M. Chen, K.S. Kim. (2001). Traversal of Candida albicans across human blood-brain barrier in vitro, Infection and Immunity, 69, 4536-4544.

Li, J., S-R. Fan, X-P. Liu, D-M Li, Z-H. Nie, F. Li, H. Lin, W-M. Huang, L-L. Zong, J-G. Jin, H. Lei, and F-Y. Bai. (2008). Biased genotype distributions of Candida albicans strains associated with vulvovaginal candidosis and candidal balanoposthitis in China, Clinical Infectious Diseases, 47, 1119–25.

Reed, B.D., P. Zazove, C.L. Pierson, D.W. Gorenflo, and J. Horrocks. (2003). Candida transmission and sexual behaviors as risks for a repeat episode of Candida vulvovaginitis, Journal Of Women’s Health, 12, 979-989.

Schmid, J., P.R. Hunter, G.C. White, A.K. Nand, and R.D. Cannon. (1995). Physiological traits associated with success of Candida albicans strains as commensal colonizers and pathogens, Journal of Clinical Microbiology, 33, 2920–2926.

Schmid, J., M. Rotman, B. Reed, C.L. Pierson, and D.R. Soll. (1993). Genetic similarity of Candida albicans strains from vaginitis patients and their partners, Journal of Clinical Microbiology, 31, 39-46.

The eternal infant

“A chimpanzee’s ability to learn is drastically reduced upon reaching maturity. But baby chimps will eagerly mimic a human caretaker – sticking out their tongues, opening their mouth wide, or making their best effort at a kissy face.” (Geoff, 2009)

A newborn creature will spend much time exploring its environment. As it comes to know its surroundings, it no longer has to acquire new information at the same rate. It loses its ability to learn.

We humans are different. We never grow up. As adults, we retain this infant-like mental plasticity, much in the same way as a child’s tolerance for milk persists into adulthood in dairy-farming societies.

Geneticists are now a step closer to understanding this evolutionary change. A team led by David Kingsley of Stanford has shown that ancestral humans lost a key piece of DNA that switches on GADD45G, a gene that stifles growth of brain tissue. In non-humans, this gene regulator slows down the growth of brain tissue:

The GADD45G regulator was active in layers of the brain where cells that ultimately form the cortex are born. Specifically, in mice and chimps, GADD45G suppresses the development of brain regions which in humans are involved in higher cognitive functions like conscious thought and language."

Completely losing GADD45G would be like losing the brakes," says Kingsley. That happens in pituitary tumours when the regulator fails and cells grow without restraint, but in healthy humans the regulatory change would have only decreased activity in specific brain areas, causing them to grow larger. (Coghlan, 2011; see also McLean et al., 2011)

This kind of genetic change may largely explain how the brain progressively expanded in ancestral humans. And this evolution did not stop with the advent of Homo sapiens. Human populations today vary at several gene loci that regulate brain growth: ASPM, MCPH1, CDK5RAP2, and CENPJ. At these loci, the most recent alleles likewise seem to favor brain growth by allowing each cortical column of neurons to expand outward over a longer period of time. Interestingly, the main result does not seem to be higher IQ, but rather some other, still unknown, enhancement of mental capacity (Frost, 2008; Montgomery & Mundy, 2010; Rimol et al., 2010; Wang et al., 2008).

Differences in mental capacity should thus steadily increase from infancy to adulthood. This is an important point. If young children perform equally well on a mental task, it is often assumed that later differences must be due to differences in the learning environment.

References

Coghlan, A. (2011). Key to humanity is in missing DNA, New Scientist, March 9http://www.newscientist.com/article/mg20928033.500-key-to-humanity-is-in-missing-dna.html

Frost, P. (2008). The spread of alphabetical writing may have favored the latest variant of the ASPM gene, Medical Hypotheses, 70, 17-20.

Geoff. (2009). Chimpanzees and Neoteny, March 30.
http://www.gmilburn.ca/2009/03/30/chimpanzees-and-neoteny/

McLean, C., Reno, P., Pollen, A., Bassan, A., Capellini, T., Guenther, C., Indjeian, V., Lim, X., Menke, D., Schaar, B., Wenger, A., Bejerano, G., & Kingsley, D. (2011). Human-specific loss of regulatory DNA and the evolution of human-specific traits, Nature, 471 (7337), 216-219 DOI: 10.1038/nature09774

Montgomery, S.H. and N.I. Mundy. (2010). Brain Evolution : Microcephaly genes weigh in, Current Biology, 20(5), R244

Rimol, L.M., I. Agartz, S. Djurovic, A.A. Brown, J.C. Roddey, A.K. Kähler, M. Mattingsdal, L. Athanasiu, A.H. Joyner, N.J. Schork, et al. for the Alzheimer’s Disease Neuroimaging Initiative (2010). Sex-dependent association of common variants of microcephaly genes with brain structure. Proceedings of the National Academy of Science. USA, 107, 384–388.

Wang, J.K., Li, Y., and Su, B. (2008). A common SNP of MCPH1 is associated with cranial volume variation in Chinese population. Human Molecular Genetics, 17, 1329–1335.

The fast runners of evolution

In the deer family, genetic variability is greater within some species than between some genera. Does Fst tell us what we think it tells us?

At almost any genetic marker (blood types, serum proteins, enzymes, mtDNA, etc.), a typical gene varies much more within than between human populations. And this is true not only for large continental populations but also for small local ones. The geneticist Richard Lewontin found that 85% of our genetic variation exists among individuals and only 15% between ‘races.’ He concluded:

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. (Lewontin, 1972)

Was Lewontin right? Some geneticists have remained unconvinced, their doubts focusing on three points:

1. A small genetic difference can still make a big cultural difference

Even if human populations differ only slightly at certain gene loci, these slight differences can still have big effects.

For instance, the historical economist Gregory Clark has argued that the slow but steady demographic expansion of the English middle class from the 12th century onward gradually raised the population mean for predispositions to non-violence, deferment of pleasure, and other future-oriented behavior. Although the nascent middle class was initially a small minority in medieval England, its descendants grew in number and gradually replaced the lower class through downward mobility. By the 1800s, its lineages accounted for most of the English population.

There then came the triumph of Victorian morality—a relatively sudden cultural change due to a genetic change that had slowly reached a point of critical mass. The English middle class could now impose its behavioral norms on the whole population, thereby abandoning the ‘two-tier morality’ of other class-stratified societies (Clark, 2007, pp. 124-129, 182-183; Clark, 2009).

2. Lewontin’s finding is true only if we look at one gene at a time

Genes vary much more within than between human populations only if we look at one gene at a time. The pattern reverses if we aggregate variation at several gene loci. The more we aggregate, the more the genetic variation will exist between populations and not within them. This point was first made by Cavalli-Sforza back in 1966 and later by Mitton (1977, 1978), Edwards (2003), and Sesardic (2010).

3. A big chunk of inter-individual genetic variation is actually intra-individual

Although only 15% of human genetic variation is composed of population differences, the remaining 85% is not necessarily between individuals. Since we are diploid organisms, some genetic variation is actually intra-individual—the differences between the genes you inherited from your mother and the genes you inherited from your father. If we factor out this kind of variation, population differences actually account for a third of all human genetic variation (Sarich and Miele, 2004).

How valid are these three points?

The first one was true historically and, presumably, prehistorically. A slight genetic advantage could indeed leverage very disproportionate benefits. “Winner takes all.” This kind of dynamic, however, is no longer legitimate in modern societies, at least not to the same extent. Although we accept that losers should lose, we don’t accept that they should lose everything. Our societies provide a wide array of redistributionist mechanisms to ensure that slight advantages don’t snowball into big ones.

The second point is certainly true. Clearly, two groups are easier to tell apart with several criteria than with one. With enough criteria, any overlap will shrink to zero and all individuals can be unambiguously assigned to either group. This is basic logic. But all this proves is that human populations are identifiable. It doesn’t prove that the differences between them are greater than the differences within them.

The third point invites the same reply of “So what?” If our intra-population variation is inflated by intra-individual variation, the same would be true for all species, and not just our own. Remove intra-individual variation, and you’ll certainly get a higher estimate of inter-population variation. But this will be true across the board. Human races will still look relatively unimportant.

In all this, a more fundamental criticism is being ignored. How meaningful is the ratio of inter-population to intra-population variation? Just what exactly does it tell us?

This ratio, called Fst, is not as meaningful as one might think:

Fst isn’t a good measure of genetic-phenotypic mediation. As a case example, Long and Kittles (2003) found a between human population Fst of 11% based on their sample; when they added chimpanzees, the between population Fst increased only to 18% [3]. Mountain and Risch (2004), citing this example, note that ‘‘a low FST estimate implies little about the degree to which genes contribute to between-group differences.’
(Occidentalist, 2011)

Indeed, some sibling species show the same kind of genetic overlap that we see between human races. And yet these species are anatomically, physiologically, and behaviorally distinct (Frost, 2008).

Remember, when two populations differentiate under the impact of diverging selection pressures, this differentiation concerns only a tiny fraction of the genome. Why? There are two reasons:

(a) Much genetic variation is of low selective value, often being little more than "junk" variability, and thus responds weakly to changes in selection pressure.

(b) Much genetic variation is equally adaptive in both of the new adaptive landscapes. There are many cases of genetic polymorphisms that widely occur not only among different populations of one species, but also among related species (Klein et al., 1998).

Fst cannot tell us how much populations really differ from each other within a species—and by ‘really’ we’re talking about adaptive differences that show up in anatomy, physiology, and behavior. It basically tells us how long these populations have been separated from each other, with some adjustment for ongoing gene flow. In our case, Fst tells us that human races are young, very young.

But this we know already. The past 40,000 years have seen our ancestors spread into a multitude of natural environments—from tropical rain forest to arctic tundra. And the past 10,000 years have seen humans enter an even greater variety of cultural and social environments—from simple horticulture to complex societies with class differentiation, State formation, urbanization, systematized religion, and the ability to store, accumulate, and exchange information via writing.

We also know that these same years have seen an accelerating pace of genetic change. Natural selection has altered at least 7% of our genome over the last 40,000 years. In particular, the speed of genetic change rose over a hundred-fold with the advent of agriculture some 10,000 years ago (Hawks et al., 2007).

The correlation is very weak between the passage of time and the degree of evolutionary change. Some organisms have remained virtually the same for millions of years. Others have changed very quickly. We, humans, are the fast runners of evolution.

References

Cavalli-Sforza, L.L. (1966). Population Structure and Human Evolution, Proceedings of the Royal Society of London. Series B, Biological Sciences, 164, 362-379.

Cavalli-Sforza, L.L., P. Menozzi, and A. Piazzi. (1994). The History and Geography of Human Genes, Princeton: Princeton University Press.

Clark, G. (2007). A Farewell to Alms. A Brief Economic History of the World, Princeton University Press, Princeton and Oxford.

Clark, G. (n.d.). The indicted and the wealthy: surnames, reproductive success, genetic selection and social class in pre-industrial England, http://www.econ.ucdavis.edu/faculty/gclark/Farewell%20to%20Alms/Clark%20-Surnames.pdf

Edwards, A.W.F. (2003). Human genetic diversity: Lewontin’s fallacy. BioEssays, 25, 798-801.

Frost, P. (2008). The 85% truism, Evo and Proud, January 4

Hawks, J., E.T. Wang, G.M. Cochran, H.C. Harpending, and R.K. Moyzis. (2007). Recent acceleration of human adaptive evolution, Proceedings of the National Academy of Sciences USA. 104, 20753-20758.

Jorde, L.B., W.S. Watkins, M.J. Bamshad, M.E. Dixon, C.E. Ricker, M.T. Seielstad, and M. A. Batzer. (2000). The Distribution of Human Genetic Diversity: A Comparison of Mitochondrial, Autosomal, and Y-Chromosome Data, American Journal of Human Genetics, 66, 979–988.

Klein, J., A. Sato, S. Nagl, and C. O’hUigin. (1998). Molecular trans-species polymorphism, Annual Review of Ecology and Systematics, 29, 1-21.

Lewontin, R. (1972). The apportionment of human diversity, Evolutionary Biology, 6, 381-398.

Long, J.C. and R.A. Kittles. (2003). Human Genetic Diversity and the Nonexistence of Biological Races, Human Biology, 81, 777-798.

Mitton, J.B. (1977). Genetic differentiation of races of man as judged by single-locus and multilocus analyses, American Naturalist, 111, 203-212.

Mitton, J.B. (1978). Measurement of differentiation: reply to Lewontin, Powell, and Taylor, American Naturalist, 112, 1142-1144.

Mountain, J.L. and N. Risch. (2004). Assessing genetic contributions to phenotypic differences among ‘racial’and ‘ethnic’groups, Nature Genetics, 36, S48 - S53.

Occidentalist (2011). Did Sarich Get It Right? Occidentalist, April 14
http://occidentalascent.wordpress.com/2011/04/14/did-sarich-get-it-right/

Sarich, V. and F. Miele. (2004). Race: The Reality of Human Differences, Basic Books.

Sesardic, N. (2010). Race: a social destruction of a biological concept, Biology and Philosophy, 25, 143-162.

Is teen motherhood pathological?

Figurine of African American grandmother and child.

Is teenage childbearing pathological? Anthropologist Linda Burton argues otherwise in her study of an African American community, and she cites other researchers who have come to similar conclusions:

Hamburg (1986) suggests that teenage childbearing, within certain poor black subgroups, reflects an alternative life-course strategy rather than a nonnormative life event. […] Furthermore, the long-term outcomes of teenage childbearing in these subcultures are not necessarily as devastating as mainstream impressions imply (Furstenberg et al. 1987). Rather, early childbearing may be perceived as a viable option that fosters individual growth, family continuity, and cultural survival in an environment in which few other avenues for enhancing development are available. (Burton, 1990, p. 124)

By viewing teenage childbearing as a reproductive strategy, with its own logic and life goals, we may better understand why it happens and know how to prevent it. Viewing it as a pathology has simply given us “solutions” that don’t work … and endless rationalizations for their failure to work.

Among African Americans, this reproductive strategy has one key characteristic: an accelerated family timetable. All life stages begin and end earlier:

Childhood: 1 to 10 years of age

Adolescence: 11 to 13

Motherhood: 14 to 26

Grandmotherhood: 35 to 45

Great grandmotherhood: 56 to 68

There is also separation of reproduction from marriage. Parenting is provided by the child’s mother and maternal grandmother. The father is usually absent. Households tend to be multigenerational with much exchange of services between younger and older generations and between siblings.

[…] given the fact that teenage childbearing families have more children per generation, it is likely that they have a broader array of potential caregivers, including older children who can assist in the care of their younger siblings, young adults who can help older family members, and young grandmothers who can parent the infants of teen mothers (Burton, 1990, p. 128)

Burton found that some African American women “covertly and sometimes overtly encouraged their teenage daughters to bear a child.” They wished to have the experience of rearing children—an experience denied them when they themselves had to rely on their maternal grandmothers many years earlier.

Once the maternal grandmother becomes a primary caregiver, the cycle of early motherhood tends to self-perpetuate. This is suggested by comments to Burton from a 35-year-old potential grandmother:

I suspect that my daughter (14 years old) will have a baby soon. If she doesn't I'll be too old to be a grandmother and to do the things I'm supposed to do, like raise my grandchild. (Burton, 1990, p. 132)

Similarly, a 58-year-old great-grandmother told Burton:

The best way to make sure that you have enough able bodies to take care of the needs in the family is to start the women having children as soon as they can. (Burton, 1990, p. 133)

Similarities and dissimilarities with the African marriage system

So far, most of the above sounds like the African system of mating and reproduction, as discussed in the last two posts. Unlike sub-Saharan Africa, however, polygyny is not institutionalized. Instead of being secondary sources of childcare, men are typically absent altogether:

In contrast to the duties of females, the role responsibilities of males in the family are ambiguous. Both the male and female respondents indicated that few familial duties are assigned to males. As young children, boys could assist girls with household tasks. Once male children reach later childhood, however, their energies are invested outside the home. Beginning at about age 10, the socialization of boys is primarily in the hands of peers and older men in the community who instruct them in the ways of survival in Gospel Hill. These instructions focus on job opportunities for black men, male/female relationships, and sexual behavior. (Burton, 1990, p. 135)

As in sub-Saharan Africa, the mother identifies first and foremost with her own kin. Unlike sub-Saharan Africa, however, she isn’t just less attached to the father. She is estranged from him, and this estrangement borders on hostility if the father consorts with white women. The following comment is from a 14-year-old mother:

Ever since I can remember I always expected to have a baby when I was 15 or 16 but I never believed I would ever have a chance to get a husband. One of the things my grandmother always said, "Pay your dues to your kin because they will take care of you. There ain't no reason to waste your time on a colored man because they don't want us no way." (Burton, 1990, p. 133)

Curiously, while citing Patricia Draper’s study on African marriage systems, Linda Burton attributes this polygyny and low paternal investment to factors that are specific to the United States. Hence, racism and the shift from manufacturing to services is said to prevent African American men from getting good jobs and becoming active fathers (Burton, 1990, p. 127).

Future of teenage childbearing among African Americans

While teenage childbearing can provide effective means of family formation, often more effective than later childbearing, it is not without its weaknesses. One of them is the willingness of maternal grandmothers to become primary caregivers. Personal autonomy is becoming a supreme value in all age groups of American society, including middle-aged and older women:

The majority of young grandmothers studied refused to assume the primary role in rearing their grandchildren. These grandmothers felt that being a surrogate parent for their grandchild did not fit with their current lifecourse activities--that included a variety of "young-adult" roles involving work, education, friendships, romance, and even their own continued childbearing. (Burton, 1990, p. 128)

Easier birth control, especially abortion, is also having an impact. Even when women wish to have children early in life, they still tend to postpone this kind of momentous decision—if given the choice.

African American fertility is now 2.2 children per woman, i.e., replacement level. And this rate is being buoyed up by a very fertile subculture of teen mothers. Most African Americans have, in fact, entered the zone of below-replacement fertility.

Conclusion

This teen mother subculture displays many elements of the African marriage system (polygyny, low paternal investment, high value placed on childbearing, strong ties with maternal kin). These elements, however, have to operate within Euro-American legal and cultural constraints, which are modeled on the marital norms of Eurasia in general and Western Europe in particular (long-term monogamy, high paternal investment, voluntary limitation of family size, relatively weak ties with kin beyond the nuclear family).

These constraints meet with varying degrees of compliance among African Americans. At one end of the continuum are those who fully comply. At the other are those who comply as little as possible, i.e., the teen mother subculture. The middle encompasses those who comply more or less.

Certain factions, notably the Black Muslims, have sought to create a new set of constraints that would be more in line with the African marriage system. But such efforts have largely failed. For the near future, at least, the teen mother subculture will become increasingly problematic, particularly as more and more older women refuse the obligations of grandmotherhood. The African American community as a whole will thus continue its slide into below-replacement fertility.

References

Burton, L.M. (1990). Teenage childbearing as an alternative life-course strategy in multigeneration black families, Human Nature, 1, 123-143.

Draper, P. (1989). African marriage systems: Perspectives from evolutionary ecology, Ethology and Sociobiology, 10, 145–169. http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1007&context=anthropologyfacpub

The African outlier

While birth rates fall everywhere else, sub-Saharan Africa remains an outlier of high fertility (2009).

Throughout most of the world, the demographic transition has played out as predicted. Fertility rates have fallen to replacement level and even lower, first in Europe and North America and more recently in East Asia, Southeast Asia, the Middle East and North Africa. The exceptions are societies where religious fundamentalists exert a strong influence on childbearing: Mormons and Amish in the United States, and Islamists in Saudi Arabia, Afghanistan, and Pakistan.

There is, however, an area where the demographic transition seems permanently stalled for reasons unrelated to religion. That area is sub-Saharan Africa. How come?

This puzzle caught the attention of anthropologist Patricia Draper back in the late 1980s. Sub-Saharan Africa had become an outlier of high fertility, even after adjustment for those factors that were lowering birth rates elsewhere. This excess fertility seemed to be due to a different social environment for mating and reproduction:

[…] in much of Africa, not only among country people but among urban populations as well, there persists high fertility and a pattern of parental investment in which both mothers and fathers invest, by Western standards, relatively little in each offspring and pursue a pattern of delegated parental responsibility (Draper and Harpending 1988). Coupled with low investment parenting is a mating pattern that permits early sexual activity, loose economic and emotional ties between spouses (Potash 1978), and in many cases the expectation on the part of both spouses that the marriage will end in divorce or separation, followed by the formation of another union (Aldous 1962; Lowy 1977; Oppong 1974; Mair 1953; Gibson 1958; Hunter 1961; Tuupainen 1970). Polygyny, still widespread in Africa, inhibits high male parental investment in children […] (Draper, 1989, p. 145-146)

In sub-Saharan Africa, parenting is assumed primarily by the mother and her kin. The parents, especially the father, are thus under much less pressure to limit family size. As Draper notes :

[…] people do not scale down expectations for large numbers of children precisely because their understandings about available resources take into account reservoirs of surrogate care among their kin. […] African men may see no urgency in reducing the numbers of their progeny precisely because a characteristically African set of socioecological circumstances permit many children to survive despite low father contribution to child support. (Draper, 1989, p. 147)

This is in contrast to the situation of parents elsewhere, particularly in modern urban settings, where a larger family perceptibly reduces the resources left over for the parents.

Will things change in the near future? Much depends on whether African families adopt the Eurasian marriage system, i.e., monogamy, long-lasting marital bonds, and high parental investment in children (including high paternal investment). To date, despite the efforts of missionaries and government authorities, there has been little change in this direction.

African men, in particular, are reluctant to assume a more active parental role:

Much of rural African subsistence is based on the work of women in their gardens; men make only modest contributions. Typically, rights in land are held by men by virtue of their membership in kinship or village units. A man who wishes to add another wife is under few constraints (provided his kinship group has the land and bridewealth), since women, in effect, pay their own way. They produce food, and they rear children. In rural areas, when a man marries an additional wife, he is awarded additional fields for this woman and her children (Bryson 1981). The importance of male labor to support such households is reduced. In former times, before colonially imposed peace, the male role in defense was important. But since central governments have been present, men who remain in rural villages spend their time in leisure, in management of household labor, or in local political affairs (Potash 1978). More recently, men absent themselves for long periods in migratory labor. They send remittances home that help to pay school and medical fees and to buy clothing. Nevertheless, the work of feeding people remains with women (Hafkin and Bay 1976; Vaughan 1983).

[…] Many efforts have been made to induce African men to increase their agricultural labor. The more successful of such ventures have followed the introduction of cash crops and the development of markets. Men are more willing to work at raising cash rather than traditional subsistence crops. However, since most cash crops are not food crops, women continue to do the subsistence farming, for which cash conversion is less possible, and they work even harder, since the men are busy with cash crops and have even less time for periodic help in the family gardens at clearing and harvest time (Obbo 1980; Whiting 1977; Kelley 1981). Characteristically, men do not return their earnings from cash crops to the household economy. This money is held separately and spent by men on their own projects (Vellenga 1983; Abu 1983; Bryson 1981). (Draper, 1989, p. 152)

As Africans migrate to other parts of the world, they tend to recreate the African marriage system in their host countries by using local people and institutions as “surrogate kin” Draper describes the situation in England, where young African couples often place their children in foster homes:

As might be expected, the outcome for all concerned does not work in the way it is expected to in West Africa. The foster parents interpret the infrequent visiting of their wards’ “real” parents as signs of parental neglect and become strongly attached to the foster children. This sometimes results in legal suits for transfer of custody to the foster parents (Ellis 1977). Meanwhile, the African parents make no comparable assumption that the delegation of care means they have surrendered formal rights in children. They consider that by having made safe and reliable arrangements for the care of children and by regular payment of fees, they are dispatching their immediate responsibility. (Draper, 1989, p. 164)

Ironically, when infertile Western couples go to Africa to adopt, as is increasingly the case, the adopted child evokes a degree of parental attachment that it would not normally evoke from its natural parents—even in the best of circumstances.

Reference

Draper, P. (1989). African marriage systems: Perspectives from evolutionary ecology, Ethology and Sociobiology, 10, 145–169.

http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1007&context=anthropologyfacpub

Are African women oppressed?

Guess who does the farmwork? In sub-Saharan Africa, women do most of the labor. On the other hand, they have more control over the fruits of their labor.

Are African women oppressed? For many, the answer is ‘yes’:

Much popular writing and many popular ideas about gender in Africa continue to rest on the belief that women in all societies in the entire world are oppressed and that African women are particularly oppressed. Even in scholarly studies, the assumption of universal male dominance of African social and economic relations persists. (Saidi, 2010, p. 12)

It’s true that women do most of the labor in sub-Saharan Africa. They are, in fact, largely self-reliant in providing for themselves and their children:

In sub-Saharan Africa, the labor of women was usually the work of daily subsistence. […] Hunting and warfare, usually the activities of men, could in contrast produce either a big windfall or nothing at all in terms of male production. […] Therefore, in a very simplistic way, it can be argued that female labor was the necessary labor—the labor from which surplus could be derived—whereas male labor could produce the luxury items, the status items. (Saidi, 2010, p. 15)

This argument ignores, however, the greater power of African women over the fruits of their labor. Often, this power was totally in the hands of women, typically older matriarchs:

The labor of young women, and young men, for that matter, in many East-Central African societies, particularly among the Sabi-speaking group of peoples, was historically controlled by the older female matrilineal kin of the young women, not by men at all. (Saidi, 2010, p. 16)

Indeed, one could argue that African men tended to occupy a peripheral role within the family:

Poewe found in her fieldwork that the marriage institution was highly flexible and discouraged strong, intense, or lasting solidarity between husband and wife. The male in these matrilineal societies did not produce for his progeny or for himself, but usually for a matriclan with whom he might or might not reside. His role, as husband, was to sexually satisfy and impregnate his wife and to take care of her during her pregnancies, but under no circumstances should a man be the object of “exclusive emotional investment or focus of attention. Instead, women are socialized to invest their emotions and material wealth in their respective matrilineages.” (Saidi, 2010, p. 16).

This situation has changed since the colonial era, largely under the impact of Christianity and Islam. Efforts have been made to restructure the African family, specifically to make the marriage bond monogamous, exclusive, and longer-lasting and to increase paternal investment in offspring.

Interestingly, there is evidence that this trend actually began some two centuries before the colonial era. Previously, the African family had been even more matrilineal, matrilocal, and matriarchal:

Murdock proves beyond reasonable doubt that the most ancient form of unilineal descent among the Niger-Congo, and therefore among the Bantu-speaking peoples (whose languages belong to the Niger-Congo family), was matriliny. He specifically reconstructs this feature for the proto-Bantu. He demonstrates it through his mapping of the scattered, relict preservation of matriliny all across the Niger-Congo-speaking regions, even in the Kordofanian branch of the Niger-Congo languages, which is spoken far away from the rest of the family in Sudan.

[…] The oral traditions of the Kanyok, who belong to the Central Savanna Bantu subgroup, still remember their shift from matrilineal to patrilineal descent a number of centuries ago, as John Yoder reveals. Most telling of all, the founders of the clans of the Gikuyu of Kenya are female, even though today the Gikuyu are strongly patrilineal. By definition, matrilineal clans must have female founders; therefore, this is undisputed evidence for prior matriliny among the Bantu-speaking peoples of the eastern Kenya highlands.

[…] The historical priority of matriliny among the Niger-Congo peoples in general—as well as among peoples speaking languages of the Bantu subgroup of Niger-Congo—is extensively and convincingly demonstrated by the comparative ethnographic evidence. Recent work in linguistic reconstruction directly supports the view that the early Bantu communities, who established themselves successively more widely in the rainforest and then in the southern savannas and eastern Africa during the last three thousand years BCE, observed unilineal descent in the form of matrilineages and/or matriclans. (Saidi, 2010, pp. 13-14)

According to Saidi (2010, pp. 12-19), sub-Saharan Africa saw a relative shift of power from women to men from around 1500 onward—apparently as a result of warfare induced by the slave trade. On the one hand, war enhanced the prestige of men through the plundered wealth they brought to their communities. On the other, women looked to men for protection during times of war.

Was there previously, then, a golden age of non-oppression? And are African women now oppressed? In truth, words like ‘oppression’ are easily abused in a context where the goal of life is not self-maximization. Yes, African women produce far beyond their own needs, but the economic surplus goes primarily to their children. If anyone is getting something for nothing, it is surely the children.

But that’s not how Africans themselves see it—or for that matter humans in any traditional society. Children are literally seen as the ‘after-life.’ It’s not out of masochism that African mothers make sacrifices for them. It’s out of a profound belief that “no one gets out of here alive”—other than one’s children and their descendents.

Reference

Saidi, C. (2010). Women’s Authority and Society in Early East-Central Africa, University of Rochester Press.

Skin color and the discrimination paradigm

Lighter skin color correlates with higher earnings among new immigrants to the U.S. This correlation holds up even if one controls for English language proficiency, education, occupation before migrating to the United States, and family background. It even holds up among immigrants of the same ethnicity, race, and country of origin. For some social scientists, only one possible explanation remains: discrimination.

The modern American credo blames underachievement by minorities on the majority, specifically through discrimination. The causal relationship may be direct, i.e., some people are consciously assigned to lower-paying jobs simply because of their skin color. Or it may be indirect, as Gunnar Myrdal argued almost seventy years ago in An American Dilemma:

The mechanism that operates here is the “principle of cumulation,” also commonly called the “vicious circle.”

[…] White prejudice and discrimination keep the Negro low in standards of living, health, education, manners and morals. This, in its turn, gives support to white prejudice. White prejudice and Negro standards thus mutually “cause” each other.

[…] If, for example, we assume that for some reason white prejudice could be decreased and discrimination mitigated, this is likely to cause a rise in Negro standards, which may decrease white prejudice still a little more, which would again allow Negro standards to rise, and so on through mutual interaction. If, instead, discrimination should become intensified, we should see the vicious circle spiraling downward. (Myrdal, 1962, pp. 75-76)

Originally, this ‘American dilemma’ was supposed to explain underachievement by African Americans. Today, it is increasingly extended to immigrants, even newly arrived ones. This is the premise of a recent study by Joni Hersch (2008):

[…] most new legal immigrants to the United States have darker skin color than white U.S. natives and are on average shorter. This article considers whether skin color and height affect economic outcomes among new legal immigrants to the United States. (Hersch, 2008, p. 346)

To this end, Hersch consulted the New Immigrant Survey 2003. The survey involved interviewing a nationally representative sample of immigrants as soon as possible after they got permanent resident status. Among other things, the immigrant’s skin color was measured with a color scale: a series of increasingly darker hands numbered from one to ten. Interviewers were given the following instructions:

As you know, human beings display a wide variety of physical attributes. One of these is skin color. Unfortunately discrimination on the basis of skin color continues to be a reality in American life. Substantial evidence suggests that lighter skinned people fare better in a variety of social and economic settings than those with darker skins. In order to detect such discrimination, it is important that the NIS include a measure of skin color. We therefore ask interviewers to use the Scale of Skin Color Darkness as a guide to rate the skin color of each respondent on a scale of 0 to 10, where 0 is the lightest possible skin color (such as that of an albino) and 10 is the darkest possible skin color” (Hersch, 2008, p. 361)

After analysing the data, Hersch found the following:

[…] I find strong evidence that darker skin color is associated with lower wages, taking into account a wide array of demographic and productivity-related characteristics such as English language proficiency, education, occupation before migrating to the United States, and family background, as well as ethnicity, race, and country of origin, which are themselves highly correlated with skin color. Immigrants with the lightest skin color earn on average 17% more than comparable immigrants with the darkest skin color. On average, moving from the 10th percentile to the 90th percentile of the distribution of skin color within ethnic or racial groups would reduce wages by about 7%-9%. These magnitudes are roughly similar to the black-white disparity and Hispanic-non-Hispanic disparity reported in Altonji and Blank. (Hersch, 2008, p. 346)

She concluded: “The results indicate that any such discrimination is not merely ethnic or racially based nor due to country of birth. […] Skin color is not merely capturing the effects of ethnicity, race, or country of birth but also has an independent effect on wages.”

Why does skin color have greater explanatory power than race, ethnicity, or country of origin? One reason is that these other variables are often problematic. ‘Blacks’ include anyone with some ancestry from sub-Saharan Africa. ‘Hispanics’ encompass a wide range of populations. At one end, there are Amerindian groups in Guatemala and southern Mexico who use Spanish as a second language. At the other, there are Italian, German, and Jewish communities in Argentina who still maintain strong links with Europe.

Similar objections could be raised for country of origin. Hersch’s data show that 18.2% of immigrants from the United Kingdom self-identify as ‘non-white’ (Hersch, 2008, p. 355). There are similarly large non-European communities in France, Belgium, the Netherlands, Norway, and Sweden. In an increasingly globalized world, what does it mean to be ‘French’, ‘Dutch’, or ‘Norwegian’?

Interestingly, 1.7% of ‘Polish’ immigrants in the U.S. are actually Hispanic (Hersch, 2008, p. 355). This should be no surprise. Eastern European universities, with their low tuition, attract large number of Third World students. Many remain after graduation before eventually moving on to a third country, like the United States.

So to explain economic success among new immigrants, we should look at their skin color rather than their ‘race,’ ‘ethnicity,’ or ‘country of origin’. Does it follow, then, that color prejudice is the ultimate cause? Or do some immigrants fare poorly because they are less able? Hersch (2008, p. 378) reports some evidence for the second explanation:

The possible connection between skin color and ability has been examined using the 1982 GSS, which includes a 10-item vocabulary test as well as a measure of skin color for a sample of about 500 African Americans. Using these data, Lynn (2002) reports a positive correlation between lighter skin color and higher test scores.

But this kind of explanation strikes her as being faulty:

However, using the same data, Hill (2002) demonstrates that controlling for education and family background eliminates the relation between skin color and test scores. […] Available evidence in the scientific literature does not support a link between skin color and intelligence. In addition, the correlation between skin color and ancestry varies considerably, with low correlations in many populations of mixed ancestry (Parra, Kittles, and Shriver 2004). In the absence of genetic evidence or a high correlation between skin color and ancestry, it seems unlikely that inclusion of test scores as a measure of ability would greatly alter the skin color effects found in this article.

This is more than a bit disingenuous. First, saying that some immigrants are less able than others doesn’t necessarily imply a genetic explanation, even if they share the same ethnic background and supposedly differ ‘only’ in skin color. A Mayan immigrant from Guatemala may be as Hispanic as a Jewish immigrant from Buenos Aires, but the two individuals bring very different attitudinal and behavioral tools for survival in a modern market economy.

Second, a genetic explanation doesn’t imply a direct causal link between skin color and intelligence. Skin color is just an indicator of one’s ancestral gene pool, which may statistically differ from other gene pools for any number of heritable traits, including those that influence intelligence. It’s also disingenuous to claim that skin color is weakly correlated with ancestry by referencing a study done on a population that has been intermixed over many generations. If a British immigrant has brown skin, the chances are very good that he or she is not of European origin.

Finally, it’s disingenuous to treat discrimination as a default explanation that should be accepted unless there is strong evidence to the contrary. This is in contrast to evidence for discrimination, which is usually inferred. For instance, Hersch (2008, p. 368) notes:

An analysis shows that those with darker skin color are less likely to be self-employed, controlling for the same predetermined characteristics used in the regression equations reported below. While it might be tempting to interpret this finding as suggestive that immigrants with darker skin color avoid self-employment out of concern about customer discrimination, there is no information in the data regarding customer contact, and there is limited empirical evidence of customer discrimination in the literature generally, so it seems wisest to avoid making this leap.

The above interpretation doesn’t strike me as “tempting.” Self-employment is typically a refuge for those who have been excluded from the job market. I remember many young people who turned to self-employment in the 1980s and early 1990s because they had no alternative. All of the stable jobs were reserved for older workers with seniority. But for Hersch, self-employment shows you’ve had more freedom to choose your livelihood.

Another point deserves mention here. When I think of self-employed immigrants, I readily think of Sikhs, Lebanese, Chinese, Armenians, and other ‘middleman’ minorities. Yes, they’re lighter-skinned than most immigrants. But do they choose self-employment over wage labor because they face little or no discrimination? That’s not my impression.

Conclusion

The discrimination paradigm was first applied to a minority that had suffered centuries of unequal, prejudicial treatment. Bit by bit, and somewhat unthinkingly, it has been extended to other groups: Amerindians and Mexican Americans and, now, newly arrived immigrants. Discrimination is no longer supposed to exercise its crippling effects through generations of enslavement and Jim Crow. After all, we see these effects in people who’ve just arrived.

Well, why not look just a bit further ‘upstream’? These different patterns of economic behavior also exist in the immigrants’ home countries. They exist worldwide. They have nothing to do with whatever prejudices White Americans might have.

But why do these patterns exist? Why should lighter skin improve one’s ability to perform in a modern market economy? Surely that proposition is just as absurd.

Actually, no. Please hear me out before you start shouting. Success in a modern market economy depends on the ability to plan ahead, and that ability has been favored outside the tropics—in areas where people tend to be lighter-skinned. The non-tropical zone has a yearly cycle that makes planning necessary. This cycle began to impact human survival as early hunter-gatherers spread into the temperate and arctic zones. It became even more important when their descendents took up agriculture. The fall harvest had to last until early summer; otherwise you and your family would starve (Frost, 2010; Frost, 2011).

The same yearly cycle also made men necessary for family survival, particularly in winter when hunting used to be the only other means of sustenance. This is in contrast to the tropics, where year-round agriculture enabled women to provide for themselves and their children with minimal male assistance. In such circumstances, men spent more time and energy seeking additional mates (Frost, 2008).

Are these patterns of behavior genetic? Or are they learned from one’s cultural environment? From the standpoint of natural selection, the question is unimportant. What works works, and what doesn’t doesn’t. But the question does matter to curious humans. To find the answer, the first step is to admit that the question is legitimate. Are we ready to take that step?

References

Frost, P. (2011). Religiosity and the origins of civilization, Evo and Proud, January 21
http://evoandproud.blogspot.com/2011/01/religiosity-and-origins-of-civilization.html

Frost, P. (2010). Out of North Eurasia, Evo and Proud, May 27
http://evoandproud.blogspot.com/2010/05/out-of-north-eurasia.html

Frost, P. (2008). Sexual selection and human geographic variation, Special Issue: Proceedings of the 2nd Annual Meeting of the NorthEastern Evolutionary Psychology Society. Journal of Social, Evolutionary, and Cultural Psychology, 2(4),169-191.http://www.jsecjournal.com/articles/volume2/issue4/NEEPSfrost.pdf

Hersch, J. (2008). Profiling the new immigrant worker: the effects of skin color and height, Journal of Labor Economics, 26, 345-386.

Myrdal, G. (1962). An American Dilemma, New York: Harper & Row.