A few years ago, my wife Mary and I found ourselves exploring a vast and remote archaeological area of Northern New Mexico called Chaco Canyon. We were fortunate enough to stumble upon a tour, guided by a National Park archaeologist who, in his midsixties, spent his entire PhD career studying ruins in and around Chaco. He told us, “We know there were people living here and when they lived here. We know there were buildings here.” He gestured around at the obvious. “Everything else is just speculation.” He paused to allow time for this naked and refreshing honesty to sink in. Then he said, “Archaeology is informed speculation—but it is speculation nonetheless.”