If we accept all of these social, symbolic, and cognitive implications of distinctively Upper Paleolithic behavioral patterns, then the issue of exactly how these patterns of behavior and the implied mental capacities they required emerged among European populations becomes one of the most critical issues in current evolutionary and cognitive research. Broadly, we are confronted by two fairly stark and sharply polarized alternatives: that these patterns of behavior and the implied levels of associated cognition emerged by a purely internal process of behavioral and cognitive evolution among the local European populations, extending directly through the European Neanderthal line; or, alternatively, that at least the majority of the new behavioral patterns, as well as the cognitive hardware necessary to support these innovations, was due to a major influx of new populations into Europe deriving ultimately from either an African or Asian source. 29,30 It is hardly necessary to stress the importance of this issue in evolutionary terms. If the Neanderthals did independently develop the whole range of behavior that traditionally has been regarded as the hallmark of fully "modern" humans, this would arguably be the most important thing we have learned about the Neanderthals since their original discovery more than 150 years ago. What follows is an attempt to review these two alternatives, as briefly as possible, in the light of the most recent archeological and biological research.In a recent paper 31 I have attempted to explore the first of these scenarios from an explicitly Darwinian, evolutionary perspective, which puts the primary emphasis on the complex pattern of climatic and associated environmental changes that occurred in Europe around the middle of the last glaciation (the period of oxygen-isotope stage 3, from ca. 60,000 -25,000 BP 32 ) and the potential selective and adaptive effects of these environmental oscillations on the demographic, social, and other cultural patterns of the local Neanderthal Few topics in palaeoanthropology have generated more recent debate than the nature and causes of the remarkable transformation in human behavioral patterns that marked the transition from the Middle to the Upper Paleolithic in Europe. 1-11 Those of us who have argued for an effective technological and cultural "revolution" at this point in the Paleolithic sequence have emphasized three main dimensions 1,2,9,11-14 : the wide range of different aspects of behavior that appear to have been affected (Fig. 1); the relative speed and abruptness with which most of these changes can be documented in the archeological records from the different regions of Europe; and the potentially profound social and cognitive implications of many of the innovations involved. Most striking of all in this context is the abrupt appearance and proliferation of various forms of perforated animal teeth, shells, beads, and other personal ornaments, and the even more dramatic eruption of remarkably varied and sophisticated forms of art, rangi...