The Crusades helped solve the problems created by the feudal primogeniture system in Europe by reducing the number of landless younger sons who could challenge the authority of their elder brothers or cause instability in their regions. The feudal primogeniture system was a custom that gave the right of inheritance to the firstborn son, regardless of the number or gender of other children. This meant that many younger sons of nobles had no land or income of their own, and had to either join the clergy, become knights, or seek fortune elsewhere. Some of them became restless and rebellious, and engaged in private wars or raids against their neighbors.
The Crusades offered these younger sons an opportunity to gain glory, wealth, and land in the Holy Land, where they could establish their own fiefs or join the military orders. Many of them took up the cross and left Europe for the Middle East, where they fought against the Muslims for control of Jerusalem and other sacred sites. By doing so, they reduced the pressure on the feudal system in Europe and increased the power of the kings and popes who sponsored the Crusades. The Crusades also encouraged trade and cultural exchange between Europe and the Middle East, which brought new ideas and technologies to both regions.