The most contentious historical question in the country is not a dispute over whether the United States is at heart a revolutionary or conservative force in world affairs, nor a conflict over how deep was Abraham Lincoln's devotion to the anti-slavery cause, nor even a battle over the origins of the Cold War. The most contentious historical question in the United States is over what history is -- or, more precisely, how long history is.In one camp are scholars who basically agree the study of history should concentrate on what has happened in the past 2,000 years or so.In another camp is a growing group of scholars and educational activists who believe history should be taught on a 14 billion-year scale.History as viewed by David Christian, who teaches history at Macquarie University in Sydney, Australia, and holds a PhD in Russian History from Oxford, is history on an entirely different scale.Its virtue -- and I listened to 12 of Christian's lectures before coming to this conclusion -- is that it puts history into perspective. It leads you to conclude that the co-evolution of humans and domesticated animals, including livestock -- the humans changing culturally, the animals changing genetically -- is a more important passage in human history than Watergate.