Final answer:
Egypt was unified early due to its protective geography and stable economic systems, whereas Mesopotamia's diverse city-states and open geography led to delayed unification until Sargon of Akkad created the first empire.
Step-by-step explanation:
The unification of Egypt occurred early, around 3150 BCE, leading to the Early Dynasty Period. Geographical features, such as the Nile River valley bordered by deserts, provided natural protection and contributed to Egypt becoming a single state rather than a series of independent city-states. This isolation from invaders, unlike Mesopotamia, allowed for a more stable and centralized government. Economic factors, like the palace/temple redistributive system, facilitated central control by Egyptian kings.
In contrast, Mesopotamia was made up of multiple independent city-states, predominantly the Sumerians, until Sargon of Akkad united them to form the world's first-known empire around 2340 BCE. The Akkadian Empire was an important model for later empires in Mesopotamia, integrating diverse cultures, social classes, religions, and governance systems. This patchwork of city-states prior to Sargon's rule may have contributed to Mesopotamia's delayed unification.
Mesopotamia faced repeated invasions due to its more open geography, leading to periods of power and empire alternating with foreign control. This instability contrasts with Egypt's relative geographic isolation and continuity of native governance until the conquest by outside empires.