In our lifetime, a 2nd Scientific Revolution is revolutionizing knowledge of the human present. From archaeogenetics —the recovery of unknown branches of humanity, unceasing past migrations and mixings— to data science —-modifying the canonical hierarchy of ancient texts and how we understand them—, the new scientific revolution also expands what we can know about the human past even as, paradoxically, truth itself and scientific expertise seem under widespread assault. The view from Harvard’s Initiative for the Science of the Human Past is that the consilience of disciplines and the consilience of data are destabilizing old understandings of fields and civilizations even as the nascent integration of science and the humanities promises to overcome C.P. Snow’s dilemma of the “Two Cultures.”  The collaboration of science, history and archaeology in paleoenvironmental investigations has opened a magnificent new path through the present into the past. Discovering the past climates within which human societies took shape is as indispensable to understanding climate change in our own time as it is critical to doing history today. These challenges erode established disciplinary boundaries and change deeply the work of scientist and humanist alike. This talk will illustrate the trajectory of historical investigation of ancient climates today and delineate the intellectual challenges before us.