With the sponsorship of the Biological Sciences section of the Institute of Catalan Studies, Neus Solé Morata, Jaume Bertranpetit, David Comas and Francesc Calafell, internationally renowned evolutionary biologists of the Institute of Evolutionary Biology (IBE), a joint UPF-CSIC centre, are the authors of a study that, based on a sample of saliva, has involved the genetic study of the y-chromosome of 2,500 men from all over the Catalan-speaking territories. Participation was voluntary and free of charge and addressed any man with a surname included in a list of 50 surnames selected for the study.

The research set out to answer questions such as why some surnames are more common than others, what is the relationship between the linguistic root of a surname and the origin of its founders, or if it is possible to predict the surname on the basis of a person's genome.

The study, has just been published, on  18 February, in the advanced edition of the European Journal of Human Genetics and has determined that the most common surnames (such as Ferrer, Soler, Vidal or Serra) are so because they were founded independently many times, while the majority of the bearers of the rarest surnames (such as Balasch, Llach or Melis) are descendants of one or few founders.

The image on the left represents the network of relations between the y-chromosomes of men with the surname Soler. Each circle represents a type of y-chromosome (haplotype); the size of the circles is proportional to the number of men who have it. The colours indicate sets of men who could be descendants of one same Soler ancestor.

As explained by Francesc Calafell, "some aspects such as cases of adoption, of false paternity, changes of surname or the inheritance of the maternal surname separate the transmission of the surname from the transmission of the y-chromosome". Indeed, another conclusion that can be drawn from this study is that, in every generation, an average of 2% of men receive the y-chromosome and the surname of different people, either through false paternity or adoption or by transmission of the mother's surname.

Why the y-chromosome in a study of Catalan surnames?

In the human genome, the y-chromosome is responsible for male sex traits. Almost all of the few genes in this chromosome are intended to encourage the development of these traits. Therefore, only men have the y-chromosome and, from one generation to another it is transmitted through the male line from father to son.

Calafell comments that "in addition, since the late Middle Ages, in Western Europe surnames have behaved similarly. It is the paternal surname that is transmitted, while women's surnames are nearly always lost".

Not all y-chromosomes are equal. Evolutionary biologists have used different types of variations and have based themselves on these differences to trace the origin of Catalan surnames. They have analysed a type of slow variation found in different frequencies in different populations and other faster variations that are almost specific to an individual or a family.

Throughout the study, the volunteers' confidentiality has been ensured using a personal code for each participant. In return, all of the people who have collaborated in the project have been able to find out the origin of their y-chromosome and, once the study was completed, they have been able to ascertain the existing relationship with the other participants, with regard to the geographical origin of their lineage.

The detailed results of the study according to each of these surnames can be found at http://cognoms.upf.edu

Reference article:

Neus Solé-Morata, Jaume Bertranpetit, David Comas and Francesc Calafell, (2015), "  Y-chromosome diversity in Catalan surname samples: insights into surname origin and frequency",  European Journal of Human Genetics, 1-9,  doi:10.1038/ejhg.2015.14.