They werent the earliest, but they were the most advancd at the time. There were humans all over the world including in North America South America, Europe and Asia, but they lived mostly hunter-gatherer existences. the 1st kingdoms started in the Fertile Cresent and North Africa because there was many more people there than just a few tribes here and there like the rest of the world. Also it was very harsh and those people were crammed into much smaller areas like living on the nile for example or living in oasis areas. Thus the need for order and control arose. Thus kingdoms and civilizations were born. The more people you have the greater chance you have for advancement because you have more random events and people comming up with new ideas. Farming for example. These people were the 1st to practice agriculture, which freed people up to take up differnt pursuits other than hunting. For example military, or learning to brew beer.