Papyrus

The entire story is more curious than what I outlined yesterday.

To begin with, the "invention" of paper by China is an interesting topic.

You may say, "Why! It may be true that paper did exist a few centuries before the time of Cai Lun, but it's plain obvious that paper was invented in China."

Oh, do not let patriotism blind your eyes. Yes, there is a wealth of archaeological discoveries of primitive paper in China, and they could be dated back to at least 100 BC. However, almost all of these ancient papers were found in Xinjiang (新疆) and Gansu (甘肅) - not the political or economic center of China in those days.

And, have you heard of papyrus (莎草纸) of ancient Egypt?

Papyrus was first manufactured in Egypt as far back as 300 BC, and had been spreading in the following centuries to middle east and central Asia. Of course, papyrus is, strictly speaking, not paper - but they have very similar ingredients. It seems highly probable that papyrus continued to spread to the East - or brought back to the Middle Kingdom by early Chinese adventurers - and was gradually modified along its journey. (After all, paper reed, the original plant that Egyptians used to make papyrus, hardly exists outside the bank of River Nile.)

By the way, Zhang Qian (張騫) stayed in the Great Yuezhi (大月氏) Empire (corresponding to Afghanistan nowadays) between 139 and 126 BC.