To understand how societies might react to climate change, archaeologists look at social responses to extreme climate events in the past—and in some places, that included measures as drastic as human sacrifice. Mass ritual sacrifices along the desert coast of northern Peru have been linked to catastrophic flooding caused by El Niño, which made researchers wonder if such sacrifices were part of a rise in violence driven by resource scarcity. But a new survey of the Lambayeque Valley suggests that violence was extremely rare, even during periods of ecological upheaval.