Final answer:
The priestly class played a crucial role in Sumerian civilization. They were religious leaders, responsible for rituals and maintaining temples, and also governed the city-states, influencing all aspects of Sumerian life. Eventually, their religious power merged with secular rule, creating dynastic authority.
Step-by-step explanation:
One significant social group in the Sumerian civilization was the priestly class. They were central to Sumerian society because Sumerians were deeply religious polytheists, each city dedicating itself to a particular patron god or goddess. Priests served not only as spiritual leaders but also as bureaucrats who managed the day-to-day operations and maintenance of the temple complexes. These sacred sites also served as the economic and political hubs of the city-states and were led by priestly governors. The priests were responsible for performing various rituals and ensuring the gods were praised and honored, which was believed to be essential in maintaining the prosperity and stability of their society. In addition, as the intermediaries between the gods and the people, they influenced almost every aspect of life in Sumer.
Over time, the power of the priestly governors evolved to include secular duties, and they began to share their authority with secular leaders and rulers. Lugals, rulers who sometimes emerged from the priestly or noble classes, eventually combined both religious and secular authority and began establishing dynasties, solidifying their power over the Sumerian city-states.