The Sumerians were the first people to migrate to Mesopotamia, they created a great civilization. Beginning around 5,500 years ago, the Sumerians built cities along the rivers in Lower Mesopotamia, specialized, cooperated, and made many advances in technology. The wheel, plow, and writing (a system which we call cuneiform) are examples of their achievements.
1 In a presidential system, the legislature and the executive do not have to be aligned and often work against each other. 2  Policy implementation can be much slower and more moderated, at least in the US system.
Whereas the prime minister has no choice because he or she is a member of Parliament and is directly accountable to that body. Herein lies a very basic difference between the presidential system of government as it exists in the United States and the parliamentary system that has evolved in Great Britain. The framers of the U.S. Constitution adopted the principle first enunciated by the Baron de Montesquieu of separation of powers.