Thanks Fts, the domestication of the apple from the wild species is an interesting case of finding naturally occurring varieties which have special or desirable qualities and their genes have then been kept in circulation by cultivating them. The silk road makes sense because it runs through many climate zones which apples tolerate well.
We all tend to judge things from the base of the familiar and in the UK we have many varieties of apple which are two hundred years old but hop across the channel to France and it is a surprise to find that the varieties, especially for cider and Calvados production, are often Gallo-Roman i.e. two thousand years in cultivation.
Btw the wild apple (aka crab) in Europe Malus sylvestris can be distinguished in hedgerows by having all white blossom whereas the domesticated apple which has often found its way there, has pink edges to the petals.