Z253 was first discovered in two men of Iberian ancestry in the 1000 Genomes Project, causing speculation that it may have arisen in Iberia and migrated to the British Isles. However its widespread distribution in the Isles and Atlantic Fringe has led to considerable speculation as to its origin.

It is apparent from the 850 or so results in the Z253 Project which are derived for Z253 that most Z253+ men of Iberian ancestry are on a specific branch of Z253, namely Z2195. The SNP pathway is Z253>Z2534>ZZ5>Z2195. Z2534 is numerically the dominant branch of Z253 and has at least two parallel branches to ZZ5, one of which leads to the large L226 (Irish Type 3) clade. ZZ5 itself has five known branches; the largest is Z2185, others are A16, BY4087 and BY25447.

In contrast to Iberian Z253, Scandinavian Z253 is scattered across multiple branches, especially branches of Z2185.
The larger Z2185 branch, BY44331, presently includes four downstream branches:
a Swedish/German branch (BY189632)
a Danish sub-branch of the FGC17551 branch (otherwise FGC17551 is southern English and Irish)
a Norwegian sub-branch of A287 (otherwise A287 is mainly Scottish and Irish, with large Ramsey and Sullivan branches)
a French sub-branch of Z2186; Z2186 is immediately upstream from the large L1066 (Irish Type 4) clade
The smaller BY44331 branch, A7037, includes a Danish/French sub-branch, BY63136.

In the A16 branch of Z2534, there is a Swedish singleton Big Y-500 result.

In the BY4087 branch of Z2534, there is a Danish singleton in one sub-branch and a French singleton in another, both of whom have tested BigY-500
There is also a Norwegian sub-branch of BY4086, which is parallel to Z2534 immediately downstream from Z253.

These Scandinavian and French-Scandinavian branches are very small numerically, each having only two or three individuals (except for the singletons specified above), but their genetic diversity within Z253 is interesting. While any of these individual branches could plausibly be the result of back-migration from the Isles to the Continent, products of the Viking slave trade or the proverbial wandering lusty Irish monks, the overall pattern may perhaps suggest a continental origin for some sub-branches of Z253.

I would be very interested to hear the thoughts of our online experts on this point.