The great paper by Brisghelli, et. al., referred to and discussed extensively below, has been updated and corrected. The updates are stunning. Now, the descendants of the once-mighty Samnites, the rugged mountain-dwellers of the Southern Italian interior, have shown to be 10% I-M26.
The corrected table can be found by clicking this link.
This pushes Samnites into third place in the M26 frequency chart. It also confirms what I've posted previously about M26 being found in large numbers among Northern Calabrian mountaineers, who have long been noted to be offshoots of the Samnites. (The Ancient sources said that the Brutti broke off from the Lucanians, and the Lucanians broke off from the Samnites. Each of these hardy tribes battle Rome for supremacy in pre-Empire Italy, and they almost won.)
But I digress. Here are the updated charts of frequency for M-26:
Sardinia ~37%
Castile ~19%
Samnium ~10%
Sicily ~7%
Basque Country ~5%
England, Ireland, and ALL W. European Islands whether Mediterranean, Atlantic, or Channel ~3%
General Italy/France ~2%
This might clear things up a bit for the spread of M26.
M26's ancestral clade, P37.2, is concentrated very strongly in the Balkans, and that all data seems to indicate that M26 followed a route
that went westward through Italy. In other words, if there had been no stop in Italy, there'd be no stop in Sardinia. No Italy, no
southern France. Thus, unless there was a back migration of M26
eastward, the M26 there is likely to be ancestral to the M26 that is
more westerly.
An eastward migration is highly unlikely, be
cause the Italian regions where it is found (South and Central
Appenines) are extremely isolated, and far from the typical coastal
routes. So it is unlikely that a few Sardinian slaves, for example, or
English pirates or whatever, spread it. Samnium and Cosenza are way up in the
mountains.
Also, there is a U5 mtDNA clade in Sardinia connected to M26 that bears evidence of an Italian refugium that
contributed (in a small way) to the post-glacial expansion of mankind
into Europe.
In other words, synthesizing the various sources, one gets: I2
likely evolved in Anatolia a very long time ago. It spread westward for sure. A major
stopping point was the Balkans, where regular old P37.2 evolved. Another stop was Italy, likely,
perhaps Piedmont, which is on the French border. M26 likely evolved
there, perhaps during a period of glacial expansion.
Alternatively, the timing of this westward spread is later, and mirrors the Cardium culture. Either way, South Central Italy (Samnium) is directly west of the Balkans. And it is isolated. A strong candidate for a similar Founder effect, like what happened in Sardinia.
From Italy, it spread to Sardinia, and points further
west. M26 then had a second expansion during the Bronze or Copper Age,
which was seaborne. Others have speculated this mirrors the Megalith culture, and I see no reason why this is not a possibility. The second spread was clearly seaborne.
I think the M26 found way up in the remote mountains of Italy is a great candidate to be ancestral to the others. We need some more research on the SNPs to solve this once and for all. As recent R1b research has shown, the STRs are not enough.
