Filser, A. & Preetz, R.
Way out of town – are long-distance relationships a response to local partner scarcity?
Individuals tend to seek and find partners who are geographically close to themselves, a pattern often described as spatial homogamy. Yet, gender-selective migration patterns have generated increasing imbalances in the local number of men and women at the main age stages of relationship and family formation throughout Europe. Yet, sex-selective migration patterns have generated increasing imbalances in the local number of men and women in the main age stages of relationship and family formation. These imbalances result in regional partner market squeezes, scarcities of potential opposite-sex partners relative to same-sex competitors. These imbalances result in partner market squeezes, local scarcities of potential opposite-sex partners relative to same-sex competitors. Individuals faced with such local scarcities of potential partners struggle to find a partner from nearby and thus might fail to realize their partner preferences. The demographic literature has long discussed the implications of local partner scarcity for the pattern and timing of relationship formation and marriage. Similarly, evolutionary approaches towards the consequences of partner market literature date back to tentative remarks by Darwin. Recent contributions to the theory on partner markets have sought to integrate these strands of literature, for instance pointing out potential sex-differences in adaptations to partner scarcity. However, the previous literature has mainly focused on analyses of the likelihood and timing of marriage. Some studies have analyzed the consequences of partner market imbalances for educational or socio-economic heterogamy. No study so far has analyzed the consequences of partner market imbalances for levels of spatial heterogamy in relationship formation. In this paper, we add a novel perspective by analyzing whether local partner scarcities predict the formation of long-distance relationships rather than short-distance relationships. Thus, we analyze whether individuals adjust their mating strategy to find individuals from geographically more distant places. We use waves 1 – 11 from the German Family Panel (pairfam) and link these data with administrative population data to measure individuals’ partner availability based on age-specific sex ratios on the county-level. Our data analysis follows a two-step approach: First, we use time-discrete multi-level models to analyze if partner market imbalances affect relationship formation. Second, we investigate if those who form a new relationship are more likely to enter a long-distance rather than a short-distance relationship in the face of an unfavorable local partner market. Results reveal that men’s chances to form a new relationship decrease if women are scarce. Moreover, results suggest that men indeed cast a wider net in the face of partner scarcities as individuals from male-skewed counties exhibit a higher likelihood to form a long-distance relationship. For women, we do not find a statistically significant association between the local sex ratio and their chances of relationship formation. Moreover, county-level sex ratios are not associated with the formation of long-distance relationships by women. Our findings hint at sex differences in the adaptations to local partner scarcities.
Willführ, K., Johow, J. & Voland,E.
Trading descendants for persistence? – Understanding the cost-benefit-ratio of consanguinity
Consanguineous relationships are widespread around the globe and may be found in historical as well as contemporary populations. For agricultural societies, it has been shown that consanguinity is associated with an increased intergenerational transmission of landholdings through the patriline. The concentration of wealth hereby might contribute to the maintenance of high family socioeconomic status as well as its ability to have and raise children to adulthood. Intermarriage is at the same time associated with fewer descendants due to a pedigree collapse and health issues due to inbreeding depression. In this paper, we develop a theoretical model to estimate the population- and niche- specific thresholds where the benefits of consanguineous marriages compensate the costs. The beneficial aspects of a consanguineous relationship are a function of the effectiveness and availability of hereditary resources; e.g. farmland. The costs are composed of a static biological component, e.g. deriving from inbreeding depression, and from a dynamic and environment-specific component which is basically the fitness detriment resulting from fewer descendants. However, a reduction of descendants and extensive kinship might be a welcome side-effect in high-K environments where cutthroat competition calls rather for offspring quality than quantity. We use historical family reconstitution data from the Krummhörn region in Germany (1720-1874) and the St. Lawrence Valley in Canada (1670-1799) as template for synthetic populations to test the explanatory power and the predictions of our model. Furthermore, we discuss the impact of socio-environmental constraints such as kin availability on the matrimonial market and cultural norms.