All of these empires grew during the Renaissance period with the introduction of trade and the use of the Silk Road. The Babylonian and Charlemagne empires had more of a competitive advantage in relying on trade, which helped the Babylonians and Romans learn from the different cultures along the trade route. The heavy taxes imposed on the population made trade or enrichment difficult. Famine caused by the flooding of the Nile hurt trade as did the plague that crisscrossed trade routes. During the Scientific Revolution, the empires of Charlemagne and Mongol gained a competitive advantage in learning. Charlemagne knew the importance of education and nurturing his people and made it one of the many achievements of his reign. The Mongols took a strong interest in science and astronomy, developing a mathematical system that is still used today and learning how the universal system provides models for how the Earth responds to weather conditions as well as the dangerous results of these models. The ancient civilization of empires represents much of the history left in the documentations that have helped astrologers and scientists explain how life that existed so long ago evolved life.