Th e stature of the fi rst anatomically modern Europeans decreases dramatically following the Last Glacial Maximum (LGM), the culminating point, around 20.000 BP, of a period of climatic deterioration that had profound eff ects on demographic, biological and economic aspects of Upper Palaeolithic populations. Declines in nutritional and life conditions are commonly assumed to play a major role in stature reduction. Th e aim of this paper is to test this hypothesis using skeletal indicators of biological and functional stress in samples from the early and late phases of Upper Paleolithic (respectively EUP and LUP), and integrating the results with the relevant archeological and paleoecological information. Analysis of biological stress markers indicates that after the LGM only a minor decline occurred in health conditions. Th is and the absence of marked or frequent growth disruptions suggests that nutritional defi ciencies alone do not explain the observed trend. Biomechanical data, however, show an increase in upper limb robusticity, indicating that LUP populations were devoting more eff ort to subsistence activities. Th ose results dovetail with archaeological information pointing to increased competition for access to resources by growing populations living in a less productive environment. Based on that, we suggest that a microevolutionary adaptive process, involving reduction in body size to reduce energy requirements and hence nutritional demands, took place in the moderately adverse conditions following the LGM.