Humans have a lot of wars. Regardless of the size or level of technological development of a group of us, we have a strong tendency to pick up weapons to go out and kill our neighbors.
Not all creatures on Earth behave like this. Animals like elephants and bonobos may fight or even kill each other from time to time, but all out wars do not occur. It seems that if such a race of creatures were to develop into an advanced, tool using society, they may form a society without war.
For a space-based RPG that I'm developing, I'd like to have just such a race of beings, but I'm unsure how evolving without war would shape both the creatures and the society. There are examples on Earth of non-warlike animals, but I'm unsure what causes these creatures to evolve this way or how a non-warlike nature would shape further development of an advanced civilization. If a race of sentient, sapient beings evolved without the need to go to war, what factors would shape and drive this evolution? What sort of evolutionary pathway would shape a race of pre-tool using creatures into an advanced society that does not fight wars, and in what major ways would the end being differ from a human?