One Of the factors that contributed to wealth in some parts of the Middle East is a surplus of

Energy

Explanation:

The Middle East is rich in oil and natural gas, which are used to create energy.

The first fundamental fact is a long-term rise in the population. The evidence that we have at our disposal indicates that probably by the middle of the 8th century, but surely by the middle of the 9th-in other words, in the Carolingian period-the population began rising