The organization of early societies changed and developed through advancements in technology, which allowed the humans to adapt and grow. Mostly every change in ancient societies started off as an advancement in technology. For example, when agriculture was developed, it allowed the hunter-gatherers to settle down for longer periods of time and increased birth rates. This eventually leads to the long-term existence civilizations and a more elaborate organization system through the rising population rates. An evidence of this would be in Ancient Sumer, where advanced irrigation systems helped the people gain the surplus of food, and as they settled down, complex institutions and specialized workers began to form, as well as other aspects of society such as different social levels. With various social levels came changes in the economy, and all those advancements eventually lead to the development of writing and record-keeping— a more and efficient type of organization. As civilizations become more advanced through different aspects such as settling down, advanced technology and specialized workers, so do the corresponding organization systems because more complex systems require a more complex system of record-keeping.