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Multiple kinship in two Spanish regions: new model relating multiple and simple consanguinity
R Calderón1, J A Peña, J Delgado
1Department of Animal Biology and Genetics, Faculty of Sciences, University of the Basque Country, Bilbao, Spain.
Human Biology
|May 26, 1998
Summary
This study analyzes multiple consanguineous marriages (MCMs) in Spain, revealing significant regional differences. A model demonstrates a dependence between MCM rates and simple consanguineous marriage (SCM) frequencies, impacting population inbreeding.
Area of Science:
- Demographic history
- Population genetics
- Anthropology
Background:
- Consanguineous marriages (marriages between relatives) have historical and demographic significance.
- Understanding patterns of multiple consanguineous marriages (MCMs) and their relationship to simple consanguineous marriages (SCMs) is crucial for population genetics.
- Previous studies have not fully explored the historical variation and interdependencies of different types of consanguineous unions.
Purpose of the Study:
- To analyze the structure and historical variation of multiple consanguineous marriages (MCMs) in two distinct Spanish regions.
- To propose and test a model demonstrating the dependence between MCM rates and the frequencies of simple consanguineous marriages (SCMs).
- To determine the impact of consanguinity on the population inbreeding coefficient (F) and analyze related genetic parameters.
Main Methods:
- Analysis of ecclesiastical dispensations for consanguineous marriages (up to third cousins) in Alava (1831-1980) and Sigüenza-Guadalajara (1861-1980).
- Development and application of a statistical model to assess the relationship between MCM rates and SCM frequencies.
- Fitting observed data to curvilinear regressions to analyze parameters like total population inbreeding coefficient (FT), contribution from SCMs (FS), and relative SCM frequency (ms).
Main Results:
- Significant differences in MCM rates were observed between the Alava and Sigüenza-Guadalajara regions.
- The proposed model supports the dependence between MCM rates for specific relationships and the frequencies of SCMs in the general population.
- Deviations between observed and expected consanguineous marriage frequencies were discussed in terms of avoidance, preferentiality, and underreporting.
- A limit for the influence of remote consanguinity on the population inbreeding coefficient (F) was established.
Conclusions:
- Historical patterns of consanguinity vary significantly across Spanish regions.
- A direct relationship exists between the prevalence of multiple and simple consanguineous marriages, influencing overall population inbreeding.
- The study provides insights into the complex factors affecting consanguineous marriage frequencies and their genetic consequences.