The correct answer to this open question is the following.
The character of Gilgamesh suggests that Sumerian society could be violent in that in refects the customs, values, and behavior of the people of Mesopotamia.
We are referring to one of the oldest pieces of literature known to man: the Epic of Gilgamesh, from the times of Mesopotamia. Gilgamesh was the King of Uruk. He was half man and half God. People feared him because he committed all kind of injustices and ruled over the land as a powerful king that had no compassion. People trusted the Gods and feared them in a kind of love and hate relationship.
The character of Gilgamesh suggests that Sumerian society could be violent because he himself used to practice some very unsual activities.
For example, one of the practices he acostumed was having the "droit de seigneur", this means that he granted himself the right to bed a servant or a citizen woman before they got married with the groom. He was a very cruel and lusty king.
