I am not certain of this, but perhaps the art of glass-making was transmitted, or discovered, and lost, in various places over various times, only to be discovered over and over again.
In any event, I think these production artifacts that have been redated using current techniques (originally excavated in the 1950's at Glastonbury) are fascinating! And this article perfectly ties into my comments in the previous post -- about how with the current changes in tecnology (that, for instance, allow us to date certain types of objects much more accurately than even 5 years ago, let alone 50 years ago!) allow us to put together a more accurate and ever-changing picture of our development, both as "humans" and as cultures. More changes are on the horizon!!!
From BBC News
8 May 2012 Last updated at 05:41 ET
New research on glass fragments found at Glastonbury Abbey in the 1950s reveals the earliest archaeological evidence of glass-making in Britain.
Clay crucibles and pieces of vivid blue-green window glass were tested. The results show the pieces date from the 680s and are likely to be associated with a major rebuilding of the abbey by King Ine of Wessex.