That question is a little vague. Do you mean Western history? What do you mean by influential? The Sumerians and Babylonians did so much to establish agriculture, politics, math and writing that it is hard to dismiss their influence. Then there is the question of how much did Arabs preserve and and invent, introducing and reintroducing knowledge after the Dark Ages. How much does the invention of the wheel, writing, agriculture or say...cheese influence culture? I would say I am constantly surprised by the long lasting influence of many cultures and it is interesting to try to tease out the threads of our history and see how we are all deeply connected.