L2 is of particular interest as it's a relatively late marker and descends from R1b-U152 which is considered by many an Italo-Celtic marker. What interests me is the distribution of R1b-U152 L2 subclades that are found at higher frequencies outside major Roman settlements. The U152 subclades project is proving of value in this respect as we can see in this
table. France and Germany appear to have higher frequencies of L2 than Italy suggesting that L2 may have something to tell us about the spread of pre-Roman R1b-U152.
This would be possible if R1b-U152 originated in Italy which has not been determined yet, in fact most speculate that it originated in the Hallstatt and La Tène cultures. This would explain why we are beginning to find such high frequencies of L2 in regions proximal to non-Italic, Alpine regions connected to the Hallstatt/La Tène culture.
Not sure if Z36 or Z56 are strongest in Roman centers but I'm interested in finding out more about your source as I'm looking for info specifically linked to these subclades. The U152 Subclades Project has presently got Switzerland (Z36, 27%) and Iberia (Z56, 33%) with the highest frequencies.
Would be interesting to see the subclade frequencies for these areas.
This would be a worthwhile exercise, thanks for suggesting it. I plan to do something similar when the subclade frequencies become more readily available.
The following caught my attention in the link you posted. A large sample of 948 men in Brabant and 643 in Poland were R1b-U152 and more than 2/3 of them were found to be +L2. This contrasts rather nicely with approximately 1/3 for Italy which had a sample of 661 men with R1b-U152.
I don't know where U-152 originated...I've seen reasoned speculation that puts the first expansion, which has more chance of actually being determined, somewhere in southeast France, northwest Italy, but it could be that it happened in the central Alps perhaps, or even a bit east.
I have more confidence in the fact that it was most probably already in Italy by the late Copper Age/early Bronze Age.
IBD analysis like that of Ralph and Coop support this position at least to the extent that there was very little inflow into Italy post 4-500 years B.C., so I think that lets out any significant "Germanic" contribution.
I'm also unpersuaded that most of it came with the first millennium B.C. so called "Celtic" or "Gallic" migrations, as it shows up far too frequently in areas that never experienced those migrations. Although, of course, modern distributions are not ideal for measuring these things, as even in Italy, we have had gene flow between neighboring regions, I don't think that would be enough to account for the high levels into the center and south of Italy. So, unless some contrary evidence should appear, I think it's most likely it was already in place by the Bronze Age.
At any rate, in 49 B.C., all of Gallia Cisalpina was granted citizenship, and so the men of that whole area would as of that date be required to serve in the legions. Actually, by 58 B.C., Julius Caesar was already recruiting troops from north of the Po to swell his numbers for the invasion of Gaul. Troops had been recruited from South of the Po even before that.
So, any legions formed in those areas after these dates would most probably have been carrying U-152, no matter when their specific lineage may have arrived in Italy, and could have spread it to whereever the legion was stationed.
In terms of the kind of analysis of which you're speaking, the difficulty is in determining whether someone's brand of U-152 came from the Romans, or the French, or the Swiss, or the Poles, who also possessed it to some degree. This is less of a problem with the non-L2 branches of U152, because they are rarer among non-Italians, although you can certainly find Z36 in high numbers in France, for example.
As I said, the presence of certain legions raised in certain areas and then deployed for long periods of time in your ancestral areas might give you more information, but I don't see how you would every really know. Although, to be honest, I didn't think we'd see this kind of progress in detailed y dna analysis.
As to the Z36 and Z56 versus the L2 numbers in Italy, while it's true that there may be proportionally more L2 in the north and particularly in the northeast than in, say, Tuscany, where the split is more even, in Brescia, for example, U152* is 62% of the total U-152. And as soon as you decide that it is an east/west split, with the east dominated by L2 and the west by U152XL2, you see that the highest L2(not L20) is in La Spezia on the west coast (25%) and Treviso (24.2%) on the east coast. My point is that there aren't simple, immutable divisions here. Someone's Z36 could come from Tuscany or Liguria or Lombardia or the Veneto although certain areas might have a higher probablitliy.
