Avoidance and prohibition of brother–sister sex in humans

Sex between full sibs is unusual in birds, mammals, and humans. These species likely possess an innate avoidance mechanism based on early proximity (i.e., the Westermarck hypothesis), and the rare occurrences may be attributable to error. Alternatively, an inclusive fitness argument shows that a low rate of sib mating may be an adaptation. The widespread occurrence of a prohibition against brother–sister sex in human societies is often invoked as evidence against an innate avoidance mechanism, since if the latter were to exist the former would be superfluous. However, given that punishing violators is costly, a prohibition is more likely to spread through an egalitarian society when the prohibited behavior is already avoided. I describe a model of the cultural dynamics of the sibling incest taboo which we have used to investigate this possibility. The predictions derived from this model are consistent with, and add rigor to, Westermarcks theory of the origin of the incest taboo.     

Distribution and abundance of sacred monkeys in Igboland,southern Nigeria

Although primates are hunted on a global scale, some species are protected against harassment and killing by taboos or religious doctrines. Sites where the killing of sacred monkeys or the destruction of sacred groves is forbidden may be integral to the conservation of certain species. In 2004, as part of a distribution survey of Sclater's guenon (Cercopithecus sclateri) in southern Nigeria, we investigated reports of sacred monkeys in the Igbo‐speaking region of Nigeria. We confirmed nine new sites where primates are protected as sacred: four with tantalus monkeys (Chlorocebus tantalus) and five with mona monkeys (Cercopithecus mona). During 2004–2006, we visited two communities (Akpugoeze and Lagwa) previously known to harbor sacred populations of Ce. sclateri to estimate population abundance and trends. We directly counted all groups and compared our estimates with previous counts when available. We also estimated the size of sacred groves and compared these with grove sizes reported in the literature. The mean size of the sacred groves in Akpugoeze (2.06 ha, n=10) was similar to others in Africa south of the Sahel, but larger than the average grove in Lagwa (0.49 ha, n=15). We estimated a total population of 124 Sclater's monkeys in 15 groups in Lagwa and 193 monkeys in 20 groups in Akpugoeze. The Akpugoeze population was relatively stable over two decades, although the proportion of infants declined, and the number of groups increased. As Sclater's monkey does not occur in any official protected areas, sacred populations are important to the species' long‐term conservation. Despite the monkeys' destruction of human crops, most local people still adhere to the custom of not killing monkeys. These sites represent ideal locations in which to study the ecology of Sclater's monkey and human–wildlife interactions. Am. J. Primatol. 71:574–586, 2009. © 2009 Wiley‐Liss, Inc.     

Taboo-based Monte Carlo Search as a Method to Improve Sampling Efficiency

Abstract

Taboo-based Monte Carlo search which restricts the sampling of the region near an old configuration, is developed. In this procedure, Monte Carlo simulation and random search method are combined to improve the sampling efficiency. The feasibility of this method is tested on global optimization of a continuous model function, melting of the 256 Lennard-Jones particles at T? = 0.680 and ρ? = 0.850 and polypeptides (alanine dipeptide and Metenkephalin). From the comparison of results for the model function between our method and other methods, we find the increase of convergence rate and the high possibility of escaping from the local energy minima. The results of the Lennard-Jones solids and polypeptides show that the convergence property to reach the equilibrium state is better than that of others. It is also found that no significant bias in ensemble distribution is detected, though taboo-based Monte Carlo search does not sample the correct ensemble distribution owing to the restriction of the sampling of the region near an old configuration.     

The function of menstrual taboos among the dogon

Menstrual taboos are nearly ubiquitous and assume parallel forms in geographically distant populations, yet their function has baffled researchers for decades. This paper proposes that menstrual taboos are anticuckoldry tactics. By signaling menstruation, they may advertise female reproductive status to husbands, affines, and other observers. Females may therefore have difficulty in obfuscating the timing of the onset of pregnancy. This may have three consequences: (a) males are better able to assess their probabilities of paternity and to direct their parental investment toward genetic offspring; (b) adulterous pregnancies are more easily detected and penalized, enhancing sexual fidelity; and (c) males avoid marrying pregnant females by relying on menstruation as evidence of nonpregnancy. This hypothesis is tested with 29 months of field data on menstrual taboos among the Dogon of Mali. Key results include the following: (a) cuckoldry is a major Dogon concern, (b) menstrual huts advertise female reproductive status, (c) husbands impose the taboos upon their wives, (d) female defiance of the taboos is undetectable and probably rare, and (e) informants think that the taboos help husbands and patrilineages to avoid cuckoldry. Thus the anti-cuckoldry hypothesis provides helpful insight into the menstrual taboos of the Dogon and should be tested among other populations. This research was supported by The Evolution and Human Behavior Program at the University of Michigan (through Dick Alexander), the L.S.B. Leakey Foundation, and the National Science Foundation (BNS-8612291). Beverly Strassmann is a National Institutes of Health postdoctoral fellow at the Reproductive Sciences Program, University of Michigan. Her primary research interest is human evolutionary ecology, with recent emphasis on menstruation in natural fertility populations, the effect of polygyny on female fitness, and reproductive endocrinology.     

Menstrual hut visits by Dogon women: a hormonal test distinguishes deceit from honest signaling

In humans the interests of males and females may conflict withrespect to the attribution of paternity. If a female has conceivedthrough adultery, or changes mates while she is in early pregnancy,she may protect her reproductive investment by misassigningpaternity. In Mali, West Africa, Dogon males attempt to preventfemale deception by mandating honest advertisement of menstruation(Strassmann, 1992). This advertisement takes place at a menstrualhut where women are on display to all the members of their husband'slineage. Knowledge of the timing of menstruation is pivotalbecause no other physiological event is as useful in paternityassessments. In this article I use hormonal data and a censusof menstrual hut visits to quantify female compliance with themenstrual taboos. The sample includes 93 women who providedurine samples twice weekly for 10 weeks. Analysis of urinarysteroid hormone metabolites (pregnanediol-3-glucuronide andestrone-3-glucuronide) demonstrates that the women went to themenstrual huts during 86% of all menses and, with the exceptionof one woman who may have been spotting, they never went tothe menstrual huts during pregnancy or amenorrhea. Thus themenstrual taboos of the Dogon were effective in eliciting honestsignals of female reproductive status (pregnant, amenorrheic,or cycling). This study is the first to use hormonal data totest the honesty of a human behavior in a nonlaboratory setting.It also establishes the feasibility of urinary enzyme immunoassaysas a tool for studying human reproduction in remote populations.[Behav Ecol 7: 304-315 (1996)]