The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000-19,000 y ago (27-19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30-13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, there were almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe.hunter-gatherers | demography | niche modeling | climate change | Paleolithic G rowing populations of anatomically and behaviorally modern humans have been partly responsible for past ecosystem changes such as the extinctions of Pleistocene megafauna and Neanderthal humans (1, 2). In addition to the destiny of other species, human population size also influences our own cultural and genetic evolution. Large pools of interacting individuals can create and maintain adaptive skills, as well as phonological variation, more effectively than small populations, and they are also capable of faster cumulative cultural evolution (3-5). A decrease in population size may even result in a loss of complex cultural traits (6). The effects of population size on cultural variation are thus roughly similar to the effects of population size on genetic variation (7).The study of the role of human population size in cultural and genetic evolution and past ecosystem changes necessitates estimates of population dynamics extending far beyond historical times. The archaeological record illustrates patterns of human population range and size dynamics (8-10), but it does not offer quantitative population size data. Archaeological reconstructions of population dynamics are also bound to the regions and time periods that offer a sufficiently rich archaeological record. In addition to archaeological data, information on past population patterns can be inferred from genetic data using skyline-plot methods (11) and pairwise or multiple sequentially Markovian coalescent analyzes (12, 13). However, these methods depend on estimates of DNA mutation rate and ...