This project will continue and elaborate an extensive electron spin resonance (ESR) dating program directed toward age determination of significant sites in Europe, western Asia and southern Africa which yield important hominid skeletal remains and/or occupation occurrences reflecting varied adaptations and behaviors of Pleistocene (or still older) hominid populations. This ESR dating program at McMaster University (Hamilton, Ontario) is the only such operation of its kind in North America. Age determination of Pleistocene hominid skeletal samples and of residues of occupation sites is critical to diverse on-going investigations directed at the elucidation of aspects of hominid evolutionary biology and phylogenesis, past cultural adaptations, inter-site correlations and the evolution of past environmental circumstances in temporally-delineated frameworks. Due to the abundance of bone/dental material in archaeological and paleontological sites the ESR method is particularly applicable to many important Pleistocene occurrences, and for ages up to several million years ago. The precision of the method is approximately %3 - %5. The method has been increasingly successfully applied by this laboratory at a diversity of Middle and Upper Pleistocene situations in Europe and western Asia and, preliminarily, in southern Africa, and provides an important resource for US archaeologists.