Evolutionary physiology is a new discipline with roots in comparative physiology. One major change in the emergence of this discipline was an explicit new focus on viewing organisms as the evolutionary products of natural selection. The shift in research emphasis from comparative physiology to evolutionary physiology has resulted in physiological traits becoming important elements in broad research programs of evolution and ecology. Evolutionary quantitative genetics is a theory-based biological discipline that has developed the quantitative tools to test explicit evolutionary hypotheses. The role of quantitative genetics has been paramount, in studying the microevolution of morphology, behavior and life history, but not comparative physiology. As a consequence, little basic information is known such as additive genetic variation of physiological traits and the magnitude of genetically based trade-offs (i.e., genetic correlations) with other traits. Here we explore possible causes for such gap, which we believe are related with the inconsistency of what we call physiological traits across taxonomic and organizational divisions, combined with logistical problems of pedigree_based analyses in complex traits