There is a very recent article which is in my view highly germane to the matters discussed on this list.... When the Worlds Population Took Off: The Springboard of the Neolithic Demographic Transition Jean-Pierre Bocquet-Appel Science 29 July 2011: 560-561. It goes over the standard ground of the Neolithic Farming Demographic Transition, discusses the community structures that emerged, migration, and most importantly the high infant mortality - low mean age situation in extended family farming settlements of that era. He also suggests an top limit of 150 persons per extended family settlement based on a putatively inherent limitation in human abilities to recognize kinship in social space beyond that population cap, which was a new argument to me. But if correct, it would help explain the wild proliferation of kinship lines in evidence on this list. To me the article contents make the explosion in the numbers of carriers of M222 (which it does NOT mention) to the present day all the more extraordinary. You have to live to reproductive age in order to pass genetic content on and that was a big challenge way back when in the British Isles. I guess this circumstance would tend to be evidence that M222 emerged later rather than earlier, well after food storage techniques had been perfected (eg. cheesemaking and beer storage) and some rudimentary understanding of water-borne illnesses was in play. But then one must also take the Black Death of the 1300s into account too. It seemly killed off half of the proto-urban population of GB leaving knots of isolated rustic communities (of possibly all fewer than 150 persons each in total) often untouched. Regretably from my point of view, the article does not discuss the role of armed conflict and raiding and mutual depredation which clearly contributed much to the complete picture. One has simply to cite the total extirpation by the Vikings of the entire Pict male line from The Orkneys and The Shetlands by simple slaughter and enslavement and transportation to the Middle Eastern slave markets to convey this importance. The article is behind a paywall but we do not let such matters bedevil us so I do have a pdf of the two pages which form quite a large file so I will not attach it.