Perhaps it's relative to the timescale - archaeology generally measures the past in terms of changes in material culture; geologists/palaeoecologists in terms of global climate change... perhaps because history (written history) is a smaller timescale, wars are the largest significant event with which to divide the records? History often chronicals political change (eg. monarchs or governments) and the changes in politics are sadly often linked to war. Good point kat - I can't actually think of historical timeline that doesn't include war somewhere on it. Then again, although war is destructive and undesirable it can lead to important technological changes and advances, and not just in weaponry.