The norm for perceived husband superiority: a cause of human assortative marriage

I have suggested that human assortative marriage for a number of variables is partially caused by behavior in accordance with two norms. Epstein and Guttman (1987) have suggested that there is no empirical evidence for these norms. In this note evidence is reviewed for the norm of perceived husband-superiority. Others have shown that the evidence for this norm is strong in regard to height, and it is shown here that the evidence is strong also in regard to age. Evidence for the norm seems suggestive in regard to IQ, education, and social class, and nonexistent in regard to physical attractiveness. With respect to height, it seems that the magnitude of the correlation between spouses is associated with the size of the breeding population to which they belong. Thus, it seems likely that the hypothesized norms are learned rather than genetically coded.     

Ethnically assortative marriage in the rural population of Tatarstan

Ethnically assortative marriage rates have been calculated for Tatars (1.16) and Russians (8.37) on the basis of 14 729 marriage records made in 1990–2000 in seven raions of Tatarstan (Arsky, Atninsky, Drozhzhanovsky, Alkeevsky, Musljumovsky, Aktanyshsky, and Baltasinsky). The outbreeding rate of Tatars (5.35%) has been found to be lower than in a number of other populations studied in this respect.     

A model for the evolution of assortative mating

Abstract: Many animals and plants show a correlation between the traits of the individuals in the mating pair, implying assortative mating. Given the ubiquity of assortative mating in nature, why and how it has evolved remain open questions. Here we attempt to answer these questions in those cases where the trait under assortment is the same in males and females. We consider the most favorable scenario for assortment to evolve, where the same trait is under assortment and viability selection. We find conditions for assortment to evolve using a multilocus formalism in a haploid population. Our results show how epistasis in fitness between the loci that control the focal trait is crucial for assortment to evolve. We then assume specific forms of assortment in haploids and diploids and study the limiting cases of selective and nonselective mating. We find that selection for increased assortment is weak and that where increased assortment is costly, it does not invade.     

Panmixia postponed: ancestry-related assortative mating in contemporary human populations

A study of two different populations reveals that in both the choice of a spouse is non-random not only in respect of broad ethnic group but also in regard to specific ancestries within that group. The cause of this surprising bias remains unclear.     

The meaning of assortative mating

Patterns of positive assortative mating are commonly inferred to result from homotypic preferences (preferences for self's type). This paper demonstrates that such preferences can result from heterotypic and type preferences as well. Because several kinds of preferences can lead to the same pattern, experimentation to measure preferences is necessary to determine the process responsible. The apparent weight of evidence for homotypic preferences may result from the kinds of preferences experimenters have selected to examine.     

The problem of the adaptive norm in human populations

The results of some investigations recently fulfilled in the framework of population-genetics approach to the problem of adaptive norm in human populations are summarized in this review. The main items considered are: methods of identification of morphologically "average" phenotypes, the role of stabilizing selection in maintaining the population adaptive norm, the problem of joint variation of monogenic and polygenic traits ant its relevance to "norm" and pathology. The significance of the concept of adaptive norm for preventive medicine and genetic monitoring is discussed.     

Sampling scale can cause bias in positive assortative mating estimates: evidence from two intertidal snails

Assortative mating in the wild is commonly estimated by correlating between traits in mating pairs (e.g. the size of males and females). Unfortunately, such an approach may suffer from considerable sampling bias when the distribution of different expressions of a trait in the wild is nonrandom (e.g. when segregation of different size classes of individuals occurs in different microhabitats or areas). Consequently, any observed trait correlation in the wild can be an artefact of pooling heterogeneous samples of mating pairs from different microhabitats or areas rather than true nonrandom matings. This bias in estimating trait correlations as a result of sampling scale is termed the scale‐of‐choice effect (SCE). In the present study, we use two intertidal littorinid species from Hong Kong to show how the SCE can bias size‐assortative mating estimates from mating pairs captured in the wild, empirically demonstrating the influence of this effect on measures of positive assortative mating. This finding cautions that studies overlooking the SCE may have misinterpreted the magnitude and the cause of assortative mating, and we provide a new analytical approach for protecting against this potential bias in future studies.     

A note of the generalizability of assortative mating coefficients for personality.

While numerous studies have reported differential assortative mating coefficients for personality traits, little research has centered on cross-sample comparisons to determine their degree of generalizability. The present investigation examines the assortative mating coefficients for scales of the Minnesota Multiphasic Personality Inventory (MMPI) from five separate studies. An examination of these patterns of significant coefficients offers little support for this cross-sample generalizability. No significant correlations resulted between these studies in their coefficients, even when the unreliability of the different measures was controlled. It is concluded that there is little evidence to support statements of differential importance in assortment for personality variables beyond the sample under investigation.     

Studies on assortative mating. III. The effects of incomplete penetrance in assortative mating systems

Four models of positive and negative assortative mating systems, exclusive or partial, in relation to phenotypes determined by a pair of autosomal alleles with dominance but with incomplete penetrance of the dominant allele in heterozygous state, are presented. By introducing the parameter of incomplete penetrance in the models of assortative matings, matings between individuals with identical genotypes will occur within the negative systems, as well as matings between individuals with different genotypes within the positive assortative mating systems. Thus, incomplete penetrance has the effect of retarding equilibrium on an assortative mating system, making this equilibrium equivalent to a system with a lower degree of assortative mating, where the penetrance equals 1 or 0. Another conclusion of biological interest drawn from the mathematical analysis presented in this paper is that for any value of the penetrance, the frequency of 0.5 for recessive individuals is also typical of exclusive or partial negative assortative mating systems at equilibrium.     

Conditions for sympatric speciation: A diploid model incorporating habitat fidelity and non-habitat assortative mating

Summary Three types of genes have been proposed to promote sympatric speciation: habitat preference genes, assortative mating genes and habitat-based fitness genes. Previous computer models have analysed these genes separately or in pairs. In this paper we describe a multilocus model in which genes of all three types are considered simultaneously. Our computer simulations show that speciation occurs in complete sympatry under a broad range of conditions. The process includes an initial diversification phase during which a slight amount of divergence occurs, a quasi-equilibrium phase of stasis during which little or no detectable divergence occurs and a completion phase during which divergence is dramatic and gene flow between diverging habitat morphs is rapidly eliminated. Habitat preference genes and habitat-specific fitness genes become associated when assortative mating occurs due to habitat preference, but interbreeding between individuals adapted to different habitats occurs unless habitat preference is almost error free. However, nonhabitat assortative mating, when coupled with habitat preference can eliminate this interbreeding. Even when several loci contribute to the probability of expression of non-habitat assortative mating and the contributions of individual loci are small, gene flow between diverging portions of the population can terminate within less than 1000 generations.