... the Industrial Revolution that is positive sum, and much that is new. Its just that the positive sum part is not the new part. The revolution in trade from luxuries to staples that saw Egypt emerge as the granary for Roman cities was positive sum ... it was, indeed, positive sum in precisely the Ricardian comparative advantage sense.

After the cold spell that allowed the Bubonic plague to climb down from the upper Nile River Valley to the Mediterranean world, that reliance on rapid transport across the Med turned from a blessing into a curse ... and undermining Justinian the Great's reconquests of North Africa, Iberia and Italy (guess who recently read Justinian's Flea?) ...

... but then after the collapse of that system emerged the North Atlantic economy built on the heavy horse-drawn moldboard plough and the three-field system, and the growth that followed from that was positive sum growth as well.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.