Something that baffles me is paper was discovered in China in the 2nd century BCE. While it was used for wrapping, it wasn't widely used for writing until, apparently, the 2nd or 3rd centuries CE. Then it took until the 7th century for it to spread to India, and until the 12th century for India to use it for writing. This is more confusing when you consider it was used for writing as early as the 9th century in the Islamic world. The Europeans seemed to have adopted it for writing the fastest after it arrived in Europe in the 11th century.
Which all begs the question...why? Why did it a.) take so long for paper to diffuse from China to the rest of Eurasia, and b.) take so long for China and India to use paper for writing after discovering it, given its obvious superiority in this regard when compared to, say, papyrus or parchment or other material to write on?