I've noticed from looking at L21 on the Yahoo group a few observations.
1- L21 can be broken into 3 groups of similiar size. The first one is the members identified as L21*(though not all are fully snp tested, they don't have the signature alleles of known downstream subclades). The second is those who are in a defined str cluster, but still without an snp discovered confirming a true subclade. The third are the members who are M222+, L226+, L193+, and so on.
2- In the first 2 groups everyone seems to average anywhere from 18-22 GD from other members in those 2 groups. I'm not sure what those GD's mean exactly, I'm thinking somewhere in the span of the bronze age, maybe around 1000BC (Urnfield period). Although L21 may have its origin ultimately in a P312 dominated Beaker timeframe, could most of today's L21 members be a result of a population explosion from a late Bronze age or early Celtic period? I think the Nordic Bronze age might explain the Scandinavian L21+, due to the Atlantic trading networks and the proximity to Urnfield.
3- The Isles, Colonials, and even some of the Scandinavians cluster closer with each other. This is not too surprising. However the French and a few other continentals seem to be the most distant from everyone else including each other. What I did find interesting is some of the Iberians, the Low Countries, and a few Germans seem to be intermediate between the more distant French group and the Isles/Scandinavians based on average GD's among L21* types.
4- The continentals have a larger percentage of L21* members than the Isles further supporting a continental origin.