This article offers a critical review of population estimates for the Neanderthal metapopulation based on (paleo-) biological, archaeological, climatic, and genetic data. What do these data tell us about putative Neanderthal demography? Biological data suggest a similar demographic frame (life-history traits, such as potential maximum longevity, age at menarche, and duration of gestation) between Neanderthals and modern humans. Archaeological data have revealed a contradiction between the mortality pattern corresponding to 45+ yr in Neanderthals and the longevity displayed by the manifest continuum of extant mammals, including primates. Paleoclimatic data suggest that the demography of Neanderthals, living as they did under highly fluctuating climatic conditions, was subject to frequent bottlenecks. This demographic instability combined with the fragmentation of geographical areas and variations in their distribution and extent could account for the fact that potential for technical creativity in the Neanderthal metapopulation would have been limited precisely because of its small numbers, leading it into what is known as a "Boserupian trap" in macrodemographic theory. Finally, genetic literature reports different--but always very low--estimations of the effective size (Ne) of the Neanderthal metapopulation. It is not easy to relate Ne to the census size of a population, but by combining different demographic values, this study produced nine different scenarios that were used to obtain an order of magnitude ranging from 5,000 to 70,000 individuals. The cause of the cultural limitation of the Neanderthal metapopulation, compared with that of modern humans, may well have resided in its small numbers alone.