Diffusion and technological change
Map above shows the spread of chess from its original invention in India to the rest of Eurasia. There is an interesting analogy here with the diffusion of a game and of technology. Technological diffusion is a slow process, but an essential one, in which a significant part of the improvements are made. Gun technology, which also started in Asia, and discussed here before, is another case in point. And sometimes the latecomer has an advantage (Gerschenkron's the advantage of backwardness, a topic also discussed by Veblen). Nothing much to say about it, just a neat map. For more on the difficulties of understanding technical change go here and here.