They also were able to get gold from Europe, able to get cotton from India. In Europe, you also had other manufactured goods, so you had this fairly vast trading enterprise emerge between these different parts of the world. And to be clear, some of the things that were traded allowed or facilitated the trade itself. I mentioned horses were a source of transportation, but camels in particular were very powerful sources of transportation, especially across Central Asia and as you get into the Middle East and Africa, because you have these large swaths of desert. Camels could not only carry a lot, but they had a lot of stamina, and they did not have to stop for water as frequently. In a lot of world history, we focus on the large, non-nomadic empires, like the Roman Empire and Han China. But as trade became more important, especially as you go through Central Asia, you could imagine that many of the people who were very good at trading, who were good at moving things, were people who were good at moving themselves, in particular, the nomadic people in Central Asia.