A new approach to historical migratory movements based on surnames: the case of Spain

A data mining technique called Self-Organized Maps (SOM) was used to select the surnames with populational information (monophyletic) to be used in the reconstruction of past demographic processes, in order to show the historical population migrations that have generated the current structure of the Spanish population. The technique made possible to identify groups of surnames with the same origin. Once the origin of each surname has been established, we can assume that each surname found outside its origin would have moved, at some point in the past, out of that original area, which allows to study historical movements. The observed movements reveal the existence of two main migratory arcs. Both migrations have moved along the coast; the first following the Mediterranean and the second following the Cantabrian Sea. It appears that these two arcs are those that have provided the backbone of the Spanish population, dividing it into two halves that would reach the limits of areas of influence of these arcs. Several types of movement have taken place (Isolation due to distance, Short-distance movements, Medium-distance movements, Long-distance movements). Those of short-medium distance have been the most frequent and most determinant in the current structure.