Predominance of extreme geographical proximity of the spouses of heirs to independent farms in a mountain valley in Norway between 1600 and 1850.

The marriages contracted between 1600 and 1850 in the parishes Vang and Slidre in the mountain valley of Valdres in Norway were investigated, using the information in the genealogical and local history of the parishes and in various public archives. The parishes functioned as a marriage isolate, in spite of regular communication with neighbouring districts. Only 54 of 4334 marriages were with residents outside the parishes, and marriages with a non-farming class (clergy) were as rare (47); 1130 marriages were probably between offspring of crofters and independent farmers. The further analysis concerns 3103 marriages contracted by the eldest sons and other heirs to 463 of the 493 farms, with members of the farming class within the parishes. Because of the linear settlement with clusters of same-named farms along both sides of the river, marital distance was measured by counting the number of farm-clusters (neighbourhood steps) between places of birth. In comparison with expectation when the marriage partner is chosen at random, marriages within the cluster occurred 13 times more frequently than expected, with an adjoining cluster 8 times more frequently and with a neighbour 1-2 clusters away 6 times as frequently as expected. One-third of the 3103 marriages were contracted within a distance of two clusters or less, and 60% eight clusters or less apart. A marital distance of 15 clusters (= 7 km) included 74% of the marriages. The predominance of a marriage pattern based on such geographical proximity must necessarily imply similarity in genetic structure of the descendants. Close consanguineous mating was apparently consciously avoided. This extreme geographical proximity of the spouses of heirs to the independent farms is probably explained by the function of a marriage as a contract to benefit the farm: promoting good neighbourliness and preventing quarrels and lawsuits related to the already very complicated ownership of cultivated land.