Environmental studies in adaptive human biology by North American anthropologists have a history of strong investigative research. From both laboratory and field work, we have gained major insights into human response to physical and social challenges. While these results were considered by most professionals to belong within evolutionary biology, in fact the intellectual structure sprang almost entirely from physiological equilibrium models. Consequently, physiological process itself was the focus. Further, most of the physiological patterns were not linked directly to important outcomes such as work output, reproductive success or survival. About 1975, American physiological anthropologists, led by Paul Baker, turned to studies of health, change and stress response. These studies were strong, but were still neither genetic nor evolutionary in intellectual structure. Evolutionary human biology was taken over by a new body of theory now called "behavior ecology", positing that selfish genes control human behavior to promote their own reproduction. This was paralleled by strong use of evolutionary theory in some areas of molecular biology. However, although physiological anthropologists have not focused on evolution, we have been developing powerful causal models that incorporate elements of physiology, morphology, physical environment and cultural behavior. In these "proximate" biocultural models, it is of little importance whether outcomes such as work or energy management are genetically based. Our future offers two major challenges. First, we must confirm causal links between specific physiological patterns and outcomes of practical importance to individuals and societies. Second, if we are to take our place in evolutionary biology, the one overarching theory of life on earth, we must understand the heritability of physiological traits, and determine whether they play a role in survival and reproduction.