Much clinical and ethnographic evidence suggests that humans, like many other organisms, are selected to avoid close inbreeding because of the fitness costs of inbreeding depression. The proximate mechanism of human inbreeding avoidance seems to be precultural, and to involve the interaction of genetic predispositions and environmental conditions. As first suggested by E. Westermarck, and supported by evidence from Israeli kibbutzim, Chinese sim-pua marriage, and much convergent ethnographic and clinical evidence, humans negatively imprint on intimate associates during (...) a critical period of early childhood.There is also much evidence that, like other social animals, humans do not seek to maximize outbreeding, but rather to maintain an optimal balance between outbreeding and inbreeding.Closeinbreeding reduces fitness through inbreeding depression, butsomeinbreeding brings the benefits of nepotism. For simple, stateless, horticultural societies, the optimal balance seems to be achieved by a combination of precultural inbreeding avoidance of relatives with anr≤·25 and cultural rules of preferential marriage with kin withr≥·25. Adjustment of the coefficient of inbreeding to other ecological settings seems to be largely cultural. An interactive model of “culture in nature” is presented, in which culture is seen as coevolving with genes to produce the maxiniization of individual inclusive fitness. (shrink)

Most studies of academic inbreeding have focused on assessing its impact on scholarly practices, outputs, and outcomes. Few studies have concentrated on the other possible effects of academic inbreeding. This paper draws on a large number of studies on academic inbreeding to explore how the practice has been conceptualized, how it has emerged, and how it has been rationalized in the creation and development of higher education systems. Within this framework, the paper also explores how academic (...) class='Hi'>inbreeding shapes and maintains a powerful academic oligarchy, leading to the stonewalling of both knowledge and institutional change to maintain social and political structures somewhat akin to those of medieval societies. The paper shows that the key to mitigating academic inbreeding practices lies in ensuring that academic recruitment processes are open, meritocratic, and transparent. However, a more difficult task is to change longstanding mentalities and disrupt a system that serves the interests of certain groups but not the advancement of knowledge or the fulfillment of universities’ social mandates. (shrink)

Due to the intense selection pressure against inbreeding, humans are expected to possess psychological adaptations that regulate mate choice and avoid inbreeding. From a gene’s-eye perspective, there is little difference in the evolutionary costs between situations where an individual him/herself is participating in inbreeding and inbreeding among other close relatives. The difference is merely quantitative, as fitness can be compromised via both routes. The question is whether humans are sensitive to the direct as well as indirect (...) costs of inbreeding. Using responses from a large population-based sample (27,364 responses from 2,353 participants), we found that human motivations to avoid inbreeding closely track the theoretical costs of inbreeding as predicted by inclusive-fitness theory. Participants were asked to select in a forced choice paradigm, which of two acts of inbreeding with actual family members they would want to avoid most. We found that the estimated fitness costs explained 83.6% of participant choices. Importantly, fitness costs explained choices also when the self was not involved. We conclude that humans intuit the indirect fitness costs of mating decisions made by close family members and that psychological inbreeding avoidance mechanisms extend beyond self-regulation. (shrink)

In this paper, the structure of a southeastern Spanish population was studied for the first time with respect to its inbreeding patterns and its relationship with demographic and geographic factors. Data on consanguineous marriages from 1900 to 1969 were taken from ecclesiastic dispensations. Our results confirm that the patterns and trends of inbreeding in the study area are consistent with those previously observed in most non-Cantabrian Spanish populations. The rate of consanguineous marriages was apparently stable between 1900 and (...) 1935 and then sharply decreased since 1940, which coincides with industrialization in Spain. A marked departure from Hardy-Weinberg expectations in the ratio of first cousin to second cousin marriages in the study population was observed. The high levels of endogamy and its significant steadiness throughout the twentieth century is noteworthy. Accordingly, our results show that exogamous marriages were not only poorly represented but also that this reduced mobility suggests that the choice of a mate was preferentially local. We found higher mobility in M22 with respect to M33 cousin mating. The relationships between population size and consanguinity rates and inbreeding fit power-law distributions. A significant positive correlation was observed between inbreeding and elevation. Many Spanish populations have experienced a prolonged and considerable isolation across generations, which has led to high proportions of historical and local endogamy that is associated, in general, with high \ values. Thus, assessing genomic inbreeding using runs of homozygosity in current Spanish populations could be an additional pertinent strategy for obtaining a more refined perspective regarding the population history inferred from the extent and frequency of ROH regions. (shrink)

Helen Dean King's scientific work focused on inbreeding using experimental data collected from standardized laboratory rats to elucidate problems in human heredity. The meticulous care with which she carried on her inbreeding experiments assured that her results were dependable and her theoretical explanations credible. By using her nearly homozygous rats as desired commodities, she also was granted access to venues and people otherwise unavailable to her as a woman. King's scientific career was made possible through her life experiences. (...) She earned a doctorate from Bryn Mawr College under Thomas Hunt Morgan and spent a productive career at the Wistar Institute of Anatomy and Biology in Philadelphia where she had access to the experimental subjects which made her career possible. In this paper I examine King's work on inbreeding, her participation in the debates over eugenics, her position at the Wistar Institute, her status as a woman working with mostly male scientists, and her involvement with popular science. (shrink)

In Portugal, research productivity is nowadays essential for the positive assessment of academics, research units and study programmes. Academic inbreeding has been highlighted in the literature as one of the factors influencing research productivity. This paper tests the hypothesis that inbreeding is detrimental for research productivity, measured through the number of publications listed in Scopus. The study resorts to a database provided by the national Agency for Assessment and Accreditation of Higher Education, which comprises all academics teaching in (...) all Portuguese institutions in the academic year 2015/2016. The sample selected for the analysis contains all academics with a PhD in Sociology. The study uses a special regression model for the analysis: the negative binomial logit hurdle. This was necessary given the large amount of academics with no publications or citations in Scopus, which were the dependent variables to assess research performance. The analysis provides separate results for the probability of inbred academics of having no papers/citations, and for the probability of producing more papers/citations than the non-inbred. Findings suggest that academic inbreeding, defined at the institutional level, has no negative effect on research productivity, contrary to what was expected. However, when defined at the national level, academic inbreeding is detrimental for the recognition and the impact of research: academics with a foreign PhD are more likely to have citations compared to academics who obtained their PhD in Portugal. A tendency was also noted that inbreeding might be more detrimental to research productivity in faculties of Economics than in Social Sciences and Humanities. (shrink)

This paper presents the results of qualitative research on academic inbreeding in Czech higher education, the first of its kind. Its focus is on exploring the significance of academic inbreeding, its types, practices, and possible solutions. The research for this paper was done among academic staff at eight institutions of higher education in the Czech Republic. It was conceptually informed by ideas about different types of inbred employees (immobile, mobile, silver-corded, and adherent) and available policy tools. The results (...) show that academic inbreeding has long flown under the radar as an issue. Its impact is perceived ambivalently, as both positive and negative, by academics and experts alike. Generally, its avoidance has not been taken into account in staff recruitment, which has allowed it to become widespread among Czech higher education institutions. The policy tools for combatting academic inbreeding include nodality (open recruitment), reorganization of recruitment procedures, capacity-building (including stays abroad), and hortatory proclamations (paying attention to the issue). Overall, the evidence gathered in the course of research suggests that some progress has been made in limiting academic inbreeding at some workplaces, and that what we would call purely immobile inbred employees are giving way to mobile and “silver-corded” inbred academic staff. Finally, Czech higher education institutions register few cases of pseudo-inbreeding, combining work at the same institution where a PhD was taken with an academically relevant position in a state research institute or the Academy of Sciences. (shrink)

Helen Dean King's scientific work focused on inbreeding using experimental data collected from standardized laboratory rats to elucidate problems in human heredity. The meticulous care with which she carried on her inbreeding experiments assured that her results were dependable and her theoretical explanations credible. By using her nearly homozygous rats as desired commodities, she also was granted access to venues and people otherwise unavailable to her as a woman. King's scientific career was made possible through her life experiences. (...) She earned a doctorate from Bryn Mawr College under Thomas Hunt Morgan and spent a productive career at the Wistar Institute of Anatomy and Biology in Philadelphia where she had access to the experimental subjects which made her career possible. In this paper I examine King's work on inbreeding, her participation in the debates over eugenics, her position at the Wistar Institute, her status as a woman working with mostly male scientists, and her involvement with popular science. (shrink)

The inbreeding coefficient of a population, estimated from ecclesiastical Roman Catholic dispensations, results from the relative contribution of different degrees of relationships (uncle–niece, first cousin, etc.). The interpopulation comparisons of consanguinity patterns may be obscured by the fact that in 1918 the Roman Catholic Church norm regulating the closest marriageable kinship was modified, limiting the application for an ecclesiastical dispensation to relatives of third degree (second cousins) or closer. Depending on the length of the period before or after the (...) change of regulation, coefficients and rates may differ. Deviation of frequencies for multiple marriages may also occur. The aim of the present paper is to determine how the chosen procedure based on ecclesiastical dispensations may affect results, regarding the inbreeding coefficient, the consanguinity rate, the structure of consanguinity and the close/remote kinship ratio. As a sample case, information from the Gredos mountain range (central Spain) has been used. (shrink)

Inbreeding introduced by R. Bakewell (1725-1795) in England for creating new animal races, was opposed by animal breeders on the Continent on religious grounds, and was soon introduced in sheep breeding for wool production in Moravia. In 1790-1840 the protagonists repeatedly rejected 'the spectre of inbreeding' and included consanguineous matching in scientific breeding. In 1836 they even formulated the research question of heredity and next year proposed the inductive method for its investigation. The achievements of sheep breeders instigated (...) German breeders to reject the dogma of the constancy of race and to elaborate the theory of individual potency. Treating heredity as the force under the influence of environment they could not solve the enigma. The question formulated in 1836 was explained in 1865 by Gregor Mendel. His theory was not perceived by animal breeders as well as by biologists up to the end of the century. (shrink)

SummaryPedigree structures of 161 uncle/niece-aunt/nephew and 4420 first cousin consanguineous marriages registered during the 19th and 20th centuries in two large and very different Spanish regions have been analysed and their genetic consequences evaluated. The frequencies of the different pedigree subtypes within each degree of relationship were quite similar in both populations despite significant heterogeneity in inbreeding patterns. The mean X-linked inbreeding coefficient for each type of cousin mating was calculated and compared to that expected for autosomal genes. (...) The effect of genealogical structure on theFx/Fradio was compared to different cultural populations worldwide. Preferentiality and avoidance of close consanguinity along with specific types of pedigrees are discussed on the basis of premarital migration and sociocultural rules still deeply rooted in certain human groups. By admitting that the observedFxcoefficient is usually higher thanFin most human populations some remarks have been made in terms of population genetic risk. (shrink)

Evolutionary theory predicts that humans should avoid incest because of the negative effects incest has on individual reproduction: production of defective offspring. Selection for the avoidance of close-kin mating has apparently resulted in a psychological mechanism that promotes voluntary incest avoidance. Most human societies are thought to have rules regulating incest. If incest is avoided, why are social rules constructed to regulate it? This target article suggests that incest rules do not exist primarily to regulate close-kin mating but to regulate (...) inbreeding between more distant kin and sexual relations between affinal relatives. Three evolutionary hypotheses about cousin marriage and affinal kin mating follow from this suggestion: Rules regulating mating between affinal kin are means of paternity protection. Cousin marriage is regulated because, if it occurs, it can concentrate wealth and power within families to the detriment of the powerful positions of rulers in stratified societies and the relatively equal social statuses of most men in egalitarian societies. Tests using the comparative method on a worldwide sample of 129 societies supported the three hypotheses. Two alternative anthropological hypotheses failed to be supported. (shrink)

During the first years of organized agricultural research in Mexico in the 1940s, two agencies ran separate programs for corn improvement. The Rockefeller Foundation's Office of Special Studies and the Mexican government's Office of Experiment Stations carried out research on corn with distinct aims and methods. That they differed strongly is well established in the literature. Many authors have discussed a Rockefeller Foundation program that reportedly emphasized hybrid corn, a technical choice that embodied a preference for assisting wealthy farmers who (...) could afford hybrid corn and the necessary agricultural inputs. Conversely, these authors attribute to the Mexican program a focus on open-pollinated corn, which presumably manifested its concern for Mexico's small farmers who saved seed. This article argues that the reverse was true. The Rockefeller Foundation program initially was committed to a type of improved open-pollinated corn while the Mexican program proceeded with a strict, U.S.-style hybrid program. I try to illuminate each group's priority on yield, as well as additional significant, and complicating, breeding priorities that precluded any collaboration between the two. (shrink)

The upheavals of late eighteenth century Europe encouraged people to demand greater liberties, including the freedom to explore the natural world, individually or as part of investigative associations. The Moravian Agricultural and Natural Science Society, organized by Christian Carl André, was one such group of keen practitioners of theoretical and applied scientific disciplines. Headquartered in the “Moravian Manchester” Brünn, the centre of the textile industry, society members debated the improvement of sheep wool to fulfil the needs of the Habsburg armies (...) fighting in the Napoleonic Wars. Wool, as the raw material of soldiers' clothing, could influence the war’s outcome. During the early nineteenth century, wool united politics, economics, and science in Brno, where breeders and natural scientists investigated the possibilities of increasing wool production. They regularly discussed how “climate” or “seed” characteristics influenced wool quality and quantity. Breeders and academics put their knowledge into immediate practice to create sheep with better wool traits through consanguineous matching of animals and artificial selection. This apparent disregard for the incest taboo, however, was viewed as violating natural laws and cultural norms. The debate intensified between 1817 and 1820, when a Hungarian veteran soldier, sheep breeder, and self-taught natural scientist, Imre Festetics, displayed his inbred Mimush sheep, which yielded wool extremely well suited for the fabrication of light but strong garments. Members of the Society questioned whether such “bastard sheep” would be prone to climatic degeneration, should be regarded as freaks of nature, or could be explained by natural laws. The exploration of inbreeding in sheep began to be distilled into hereditary principles that culminated in 1819 with Festetics’s “laws of organic functions” and “genetic laws of nature,” four decades before Gregor Johann Mendel’s seminal work on heredity in peas. (shrink)

The method of isonymy to estimate inbreeding is applied to the historical population of the Quebrada de Humahuaca . Data from the baptismal records of the Parochial Church of Humahuaca from 1734 to 1810 were grouped into two periods, 1734–72 and 1773–1810. The analysis was carried out twice: using the surnames exactly as they were registered; combining homonymous surnames which were pronounced or spelt in a similar way. The random and non-random components of inbreeding have been investigated through (...) different methods. There were no significant differences between the results of the two analyses, nor between the expected and observed isonymy. The value of Flies somewhere between those for offspring of first cousins once removed and second cousins once removed. There is a tendency for F and its components to increase through time. It is concluded that the high altitude aboriginal population of Humahuaca Parish must have behaved as a panmictic unit. (shrink)

In an earlier paper it was suggested that relationships between population density, migration, and the frequency of consanguineous marriage depended on variation in the social class composition of populations. For two valleys in the western Pyrenees, it was found that migration distances are shorter in areas with lower population density and that this could in part be attributed to the effects of social class independently of the occupations of the population. The present paper investigates further the relationships between migration, the (...) frequency of consanguineous marriage and inbreeding in the Roncal valley in Navarre, Spain, for the period 1877–1915. The Roncal valley contains seven villages, each a separate administrative unit. Almost all the total population of 3900 live in these nucleated villages and there are few isolated households. The area of the valley is 420 km2, and the population density 9·28 inhabitants/km2. (shrink)

During the first years of organized agricultural research in Mexico in the 1940s, two agencies ran separate programs for corn improvement. The Rockefeller Foundation's Office of Special Studies and the Mexican government's Office of Experiment Stations (later called the Agricultural Research Institute) carried out research on corn with distinct aims and methods. That they differed strongly is well established in the literature. Many authors have discussed a Rockefeller Foundation program that reportedly emphasized hybrid corn, a technical choice that embodied a (...) preference for assisting wealthy farmers who could afford hybrid corn and the necessary agricultural inputs. Conversely, these authors attribute to the Mexican program a focus on open-pollinated corn, which presumably manifested its concern for Mexico's small farmers who saved seed. This article argues that the reverse was true. The Rockefeller Foundation program initially was committed to a type of improved open-pollinated corn while the Mexican program proceeded with a strict, U.S.-style hybrid program. I try to illuminate each group's priority on yield, as well as additional significant, and complicating, breeding priorities that precluded any collaboration between the two. (shrink)

The term ‘breeding system’ is used to describe the morphological and behavioural aspects of the sexual life cycle of a species. The yeast breeding system provides three alternatives that enable hapoids to return to the diploid state that is necessary for meiosis: mating of unrelated haploids (amphimixis), mating between spores from the same tetrad (intratetrad mating, automixis) and mother daughter mating upon mating type switching (haplo‐selfing). The frequency of specific mating events affects the level of heterozygosity present in individuals and (...) the genetic diversity of populations. This review discuses the reproductive strategies of yeasts, in particular S. cerevisiae (Bakers' or budding yeast). Emphasis is put on intratetrad mating, its implication for diversity, and how the particular genome structure could have evolved to ensure the preservation of a high degree of heterozygosity in conjunction with frequent intratetrad matings. I also discuss how the ability of yeast to control the number of spores that are formed accounts for high intratetrad mating rates and for enhanced transmission of genomic variation. I extend the discussion to natural genetic variation and propose that a high level of plasticity is inherent in the yeast breeding system, which may allow variation of the breeding behaviour in accordance with the needs imposed by the environment. BioEssays 28: 696–708, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Two predictions concerning the perceived severity of crimes can be derived from evolutionary theory. The first, arising from the theory of inclusive fitness, is that crimes in general should be viewed as more serious to the degree that the victim is genetically related to the perpetrator. The second, arising from the deleterious effects of inbreeding depression, is that heterosexual sexual coercion should be perceived as more serious the closer the genetic relationship of victim and perpetrator, particularly when the victim (...) is a female of fertile age. Two hundred and thirty university students estimated the magnitude of the severity of brief crime descriptions in three separate studies. In the first two, the biological kinship of victim and perpetrator was varied, and in the third, the hypothetical genetic relatedness of the subject and the fictitious victim was varied. All three studies found the linear relationships between biological kinship and perceived crime severity predicted by theory. (shrink)

The Westermarck effect (sexual inhibition among individuals raised together) is argued to be mediated olfactorily. Various animals, including humans, distinguish among individuals by scent (significantly determined by MHC genotype), and some avoid cosocialized associates on this basis. Possible models of olfactory mechanisms in humans are evaluated. Evidence suggests aversions develop during an early sensitizing period, attach to persons as much as to their scents, and are more powerful among females than among males. Adult to child aversions may develop similarly, but (...) more likely result from stimulus generalization. This hypothesis accords with current evidence and yields testable predictions (e.g., anosmia will prevent inhibition) that, should they be supported, will conclusively ground the Westermarck effect in a biological mechanism. (shrink)

Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands (...) of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior. (Published Online November 9 2006) Key Words: adaptation; behavior genetics; Darwinian psychiatry; evolution; evolutionary genetics; evolutionary psychology; mental disorders; mutation-selection balance; psychiatric genetics; quantitative trait loci (QTL). (shrink)

We address the controversy in the literature concerning the definition of holobionts and the apparent constraints on their evolution using concepts from community population genetics. The genetics of holobionts, consisting of a host and diverse microbial symbionts, has been neglected in many discussions of the topic, and, where it has been discussed, a gene-centric, species-centric view, based in genomic conflict, has been predominant. Because coevolution takes place between traits or genes in two or more species and not, strictly speaking, between (...) species, it may affect some traits but not others in either host or symbiont. Moreover, when interacting species pairs are embedded in a larger community, indirect ecological effects can alter the expected pairwise dynamics. Mode of symbiont transmission and the degree of host inbreeding both affect the extent of microbial mixing across host lineages and thereby the degree to which selection on one trait of either partner affects other aspects of a holobiont phenotype. We discuss several potential defining criteria for holobionts using community genetics and population genetics models, suggesting their application and limitations. Using community genetics models, we show how conflict between genomes can be self-limiting, while cooperation and mutualism tend to be self-accelerating. It is likely that this bias in the evolutionary dynamics of interaction between hosts and symbionts is an important feature of holobionts. This bias in the evolutionary dynamic could contribute to explaining the absence of cheaters from natural mutualisms, although cheaters are predicted by gene-centered conflict theory to cause the evolutionary instability of mutualisms. Additionally, it may help explain the more frequent origin of mutualisms from parasitic than from free-living systems, an evolutionary trajectory opposite to that predicted by genome conflict theory. (shrink)

Information on the current prevalence and types of consanguineous marriages in Malakand District, Khyber Pakhtunkhwa Province (KPK), Pakistan, was collected from 1192 rural couples. Some 66.4% of marriages were between couples related as second cousins or closer (F≥0.0156), equivalent to a mean coefficient of inbreeding (α) of 0.0338. The data suggest that the prevalence of consanguineous unions in Malakand has been increasing during the last decade, in response to the high levels of violence across KPK.

This paper focuses on the inheritance of human handedness and cerebral lateralization within the more general context of structural biological asymmetries. The morphogenesis of asymmetrical structures, such as the heart in vertebrates, depends upon a complex interaction between information coded in the cytoplasm and in the genes, but the polarity of asymmetry seems to depend on the cytoplasmic rather than the genetic code. Indeed it is extremely difficult to find clear-cut examples in which thedirectionof an asymmetry is under genetic control. (...) As one possible case, there is some evidence that the direction, clockwise or counterclockwise, of rotation of the abdomen in certain mutant strains ofDrosophilais controlled by a particular gene locus, although there appears to be some degree of confusion on this point. By contrast, it is much easier to find examples in which thedegreebut not the direction of asymmetry is under genetic control. For instance, there is a mutant strain of mice in which half of the animals displaysitus inversusof the viscera. The proportion has remained at one half despite many years of inbreeding, suggesting that the mutant allele effectively cancels the normalsitusand allows the asymmetry to be specified in random fashion.Although this account does not deny that the right hemisphere of humans may be the more specialized for certain functions, it does attribute a leading or dominant role to the left hemisphere (at least in most individuals). We suggest that so-called “right-hemisphere” functions are essentially acquired by default, due to the left hemisphere's prior involvement with speech and skilled motor acts; we note, for instance, that these right-hemisphere functions include rather elementary perceptual processes. But perhaps the more critical prediction from our account is that the phenomenon of equipotentiality should be unidirectional: the right (lagging) hemisphere should be more disposed to take over left-hemisphere functions following early lesions than is the left (leading) hemisphere to take over right-hemisphere functions. We note preliminary evidence that this may be so. (shrink)

Philosophy, like modern agriculture, is a little too prone to monoculture. Happily, unpopular philosophical traditions are less in danger of complete extinction than varieties of apple, say, or breeds of pig. For this difference, however, the subject is often indebted to a few far-sighted individuals who appreciate the value of presently unfashionable ideas – who stand ready to reinvigorate the gene pool, when popular approaches succumb to pests and inbreeding.