Provoked by Luboš Motl, AKA, Lumo, the Lumonator, I have been digging into the genomic history of Spain. I found this very nice article.
A wide range of peoples have settled in Iberia since the end of the last Ice Age. Phoenicians, Celts, Greeks, Jews, Romans, Goths, Suebi, Franks, Arabs and Berbers. All have left their genetic print on the populations of the regions where they settled. This page attempts to identify their genetic markers through the use of Y-chromosomal (Y-DNA) haplogroups, which are passed on nearly unaltered from father to son, mitochondrial DNA (mtDNA), which is inherited only from one's mother, and genome-wide studies.
The modern Iberian gene pool is overwhelmingly Mediterranean, and yet the sequencing of a 7,000 year-old hunter-gatherer from La Braña in Asturias, revealed that Mesolithic Iberian shared much closer genetic affinities to modern Northeast Europeans (apart from having dark skin). This shows just how much the genetic landscape of the peninsula has changed in the course of a few eventful millennia. Yet, a single Mesolithic genome is not enough to get an unbiased picture of what all Iberian people were like at the time. It is cannot be excluded yet that North Africans hunter-gatherers may have crossed the Strait of Gibraltar on boats and colonised the Iberian peninsula from the south, while northern and central European foragers occupied northern Sp
And this on the Celtic component:
It is perhaps the wealth of Megalithic people that attracted, through the Beaker network, the Indo-European speakers from central Europe, and caused them to invade western Europe and destroy the Megalithic cultures that had lasted for several millennia. Equipped with bronze weapons and horses, these Indo-Europeans were not cereal farmers but cattle herders from the Pontic Steppe, north of the Black Sea. They had already conquered the Balkans, the Carpathians, Poland, Germany, Scandinavia and the Baltic countries between 4,000 and 2,800 BCE, causing the collapse of all the Chalcolithic and Neolithic cultures in those areas. The southern R1b branch had advanced from the Hungarian plain to Bohemia and Germany by 2500 BCE (presence of R1b confirmed by Lee at al. 2012), and continued its migration until the Atlantic coast, reaching Britain and western France by 2,200 BCE and Ireland by 2,000 BCE. These R1b men were the Proto-Celts and their Y-DNA is now found in over half of Spanish and Portuguese men.
This was a mainly male invasion, as much less maternal DNA has the Proto-Celtic signature.