I have been reading about ancient warfare recently and author Brian Ferguson looks for evidence that warfare actually had a general starting date. Looking at bones he says the evidence of death by violence increased dramatically from 12,000 BC on.
That said I intend to write about the generations before us who created weaponry, not unlike the bow and arrow with is ubiquitous, and the atlaatl.
The Atlatl was thought to have been used from Upper Paleolithic times (30,000 BC) to about 1000 AD. It is a trick of physics, a simple grooved shaft that allows the human being to add radius to a throw and fling a javelin or an arrow much further and more accurate than with arm alone.
Watch this video. It gives you a sense of how easy it was to use an Atlatl and why it is so effective. First discovered in Australia, later evidence of it has been found everywhere in Central and Southern Africa and Central America.
Sources: D. Garrod, Palaeolithic spear throwers. Proceedings of the Prehistorical Society. 21, 1955.