Begoña Martínez-Cruz et al. (2012) studied the frequencies of Y-haplogroups in the Spanish and French Basque country, Gascony, Navarra, La Rioja, northern Aragon, Cantabria, and northern Castille & Leon. There are 835 samples, making it the biggest and most detailed study for the region so far. Here is the table with the full results.
Haplogroup R1b
One major find is that
16.3% of the 558 Basque men tested (both Spanish and French + Navarra) belonged to
R1b-L21, so far associated with the British Isles and Northwest France. It is only 1/5 of all Basque R1b, but is nevertheless significant.
In Gascony, 10.75% of men belonged to R1b-L21, while it was 8.5% in the regions of Spain bordering the Basque country. Cantabria had 0% though.
The typically Basque and Spanish
R1b-M153 was found in 15.4% of the Basques, and about 8.5% in surrounding regions (again 0% in Cantabria).
The other main Iberian R1b subclade,
SRY2627, is considerably lower among the Basques (6%) than the Gascons (12%) and other North Spaniarrds (11.7%). M153 and SRY2627 seem to have opposite patterns.
The most common R1b subclade was the pan-Italo-Celtic
P312 (S116), which peaked at 42.3% in the Basques, and is found in 37.3% of the Gascons and 35.3% from Aragon to Cantabria.
There were only traces of the Germanic
R1b-U106 (S21) : 11 samples out of 835, or 1.3%. However 6 of these samples were in Gascony (France). The 1% of I1 is consistent with that.
The Alpine Celtic and Italic
R1b-U152 (S28) was tested along with two of its subclades (L2 and L20). There is no particular pattern for any of them. L2 is found at low frequencies everywhere. There were only a few samples of L20 and U152* (among the Basques all four in North Western Nafarroa). In total, U152 and suclades made up 2.3% of Basque lineages, 2.5% of Gascon lineages and 4.2% of those between Aragon and Cantabria.
Haplogroup I
The other main haplogroup of the Basques is of course
I2a1a (M26, formerly I2a1), which reaches 6.6% among the Basques, with a peak at 17% at Zuberoa and 12% at Lapurdi Nafarroa, both in the French Basque country.
One surprise is the relatively high percentage of
I2a2a (M223, formerly I2b) in Gascony (5.7%), compared to under 0.5% in Northeast Spain. It seems that the Pyrenees were a barrier to the spread of this haplogroup. Perhaps its presence in Gascony is owed to the Franks, which would mean that I2a2a wasn't found in Southwest Europe between the Paleolithic and Roman times. That would make it all the more German, and less pre-Celto-Germanic as had been suggested.
Other haplogroups
Let's note also the almost complete absence of haplogroup
R1a, T and G among the Basques (only 2 G samples and 1 T sample),
The most common subclade of
E1b1b among the Basques is the Northwest African E-M81 (1.25%) followed by the North African E-V65 (1%). Other subclades are just found at trace frequencies, even E-V13 (only 1 sample).
On the J front, the Basques have a reasonable amount of J2a (1.6%), but very little J2b (0.35%), even less than J1 (0.55%).
The absence of E-V13, T and G2a would suggest that these three haplogroups migrated together, presumably during the Neolithic. On the other hand, the presence of J2 alongside a similar frequency of R1b-U152 would hint at a Gallo-Roman origin of these two haplogroups