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.
The main difference between a parliamentary and presidential system of government is that in a presidential system, the president is separate from the legislative body, but in a parliamentary system, the chief executive, such as a prime minister, is part of the legislative body, or parliament.arliamentary Systems. The roles of head of state and head of government often are held by different people in a parliamentary system. For example, a country might have a prime minister who acts as its head of government and a monarch who acts as its head of state.