Shifts Along a Spectrum: A Longitudinal Study of the Western Eurasian Realized Climate Niche

Climate niches that modern humans and earlier hominin ancestors occupied have changed dramatically over time, but the extent of those changes has gone largely undocumented. This study investigates the manner in which the realised hominin climate niche has expanded, contracted, or stayed stationary across four time periods (Last Interglacial, Last Glacial Maximum, Mid-Holocene, and 1950–2000) in Western Eurasia. Using spatially gridded general circulation model data and site locations this study examines climate variables from archaeological sites and current Western Eurasian cities to describe both the regional Western Eurasian fundamental and realised climate niches. Changes between the three prehistoric periods and modern-day time period are analysed by calculating each realised niche breadth, overlap, position, and variance. Results indicate that as global temperatures cooled from the Last Interglacial to Last Glacial Maximum, populations expanded their climate niche breadth beyond that of earlier Neanderthal groups, shifting toward regions with less seasonal variation. Conversely, Mid-Holocene humans, who saw the proliferation of both agriculture and population, contracted their realised climate niche space. The contraction and expansion of realised climate niche space illustrates how hominins have evolved the capacity to shift their niche through changes to their subsistence strategy and adaptations to overall climatic conditions.