Mate choice in Olivenza: influence of border change on Spanish-Portuguese lineages.

The mating pattern in a population determines the next generation gene pool and therefore its genetic structure. Besides socio-cultural and geographic factors, political barriers may influence the formation of couples. The present paper studies how the change of national border affected the mating pattern of Olivenza in Badajoz Province (Spain), which experienced a change of domain from Portugal to Spain in 1801. For the period analysed (1750-1850), 954 Catholic marriage records were transcribed. Data were sorted by decades in order to make a temporal study possible and analysed by means of diversity and repeated-pairs of surnames. Following the change of border the mating pattern modified. Coinciding with a larger number of mixed marriages with Spaniards, there was a progressive rise in the diversity of surnames. From 1811 to 1820 the analysis of repeated-pairs of surnames indicates the existence of preferential matings within Spanish and Portuguese lineages. After 1821 the above pattern became less clear due to the disappearance of the Spanish-Portuguese restrictions on choice of mate.