The relationship between surnames and Y chromosomes – both passed down from father to son – has previously been researched in Britain and Ireland; this study is the first to look at Spain.
The study revealed, perhaps unsurprisingly, that a large number of men bearing uncommon surnames share similar Y chromosomes.
The analysis also showed that as a surname becomes more common, the correlation with the Y chromosome gradually disappears – indicating that that common family names do not represent men from the same family line.
The study used DNA samples from over 1,766 male volunteers bearing 37 Spanish surnames representing a wide geographic coverage and a broad spectrum of frequency.
The surnames were classified into 5 groups:
very common: surnames with over 150,000 bearers nationwide (e.g. Fernández, Martínez).
common, surnames with between 15,000 and 150,000 bearers nationwide (e.g. Aguirre, Díez).
uncommon: surnames with between 5,000 and 15,000 bearers (e.g. Tirado, Ibarra).
rare: surnames with between 3,000 and 5,000 bearers (e.g. Bengoechea, Cadenas).
very rare: with between 100 and 3,000 bearers (e.g. Nortes, Albiol).
Lead author of the study Dr Conrado Martínez-Cadenas of the Jaume I University in Castellón explained:
“There is a strong relationship between the surname and the Y chromosome in Spain. The majority of men who share relatively unusual family names – those carried by less than 6,000 people in all of Spanish national territory – also tend to share an identical or very similar Y chromosome, thus demonstrating that these surname carriers descended from the same original bearers of those paternal surnames.”
“The data show that the correlation or coancestry between the surname and the Y chromosome does not at all depend on the geographical origin (Castilian, Catalan or Basque) nor the type of surname (derived from the father’s name, a place name, a profession, a nickname, a physical trait). It only depends on the frequency of the surname”.
The study said that the Spanish surnames are estimated to be an average of 536 years old, though individual surnames vary between 200 and 800 years old.
Dr Martínez-Cadenas said: “This age is calculated by determining the most recent common ancestor of study participants with a particular surname. This is not the true age of the surname, however, but rather the point in time when study participants of the same surname had the most recent common ancestor in the direct male line”.
The study compared the Spanish results to previous British and Irish studies. They found the correlation patterns between surnames and Y chromosomes in Spain were similar to those in Britain, but different from those in Ireland.
Dr Martínez-Cadenas said: “The analyses indicate that the Irish surnames are much older than those from Spain and the United Kingdom, in addition to presenting a correlation that does not depend on surname frequency. In Ireland, some very common surnames present a strong correlation between surname and the Y chromosome – something that is not observed in Spain or the United Kingdom- while others do not”.