What wave of migration do British Isles J1's represent?

[JAFarris]

I was wondering if anyone knew what the British Isles J1's are supposed to represent, historically speaking?  I know they are supposed to be prominent in the introduction of agriculture into Europe in the Neolithic period, but does this mean they were instrumental in forming the cultures who produced dolmens, Stonehenge, etc?  Or did they perhaps arrive later, even perhaps with the Roman invasion?  What explains the frequency of J1 in Western Britain, particularly? 

[Rob Hausman]

This is a question that mito DNA haplotypes -at this level of resoluion- cannot really answer.  Considerable evidence shows that the British Isles were settled about 8 times from 700 K to 12 K years ago and only the last settlement stuck as all the others were wiped out by subsequent ice ages.  By 12 K
years ago -after the last ice age- the populations of Europe had mixed considerably and the same Y and mitochondrial haplotypes can be traced back to Slovakia and Spain or France, thus of not much use for recent origin.  The simple answer to your question is the last migration but I doubt that this gets at what you really want to know.  Haplotype J -I know less about J1- represent a  European population that likely ws resident in Europe before the neolithic revolution and which interbred with the invaders from the middle east.