An understanding of the factors governing grass–tree coexistence in savannas and exclusion of trees in grasslands remains elusive. We contend that progress in understanding these factors is impeded by a reliance on a falsification approach and an excessive concern over type I errors (false positives), which results in premature rejection of hypotheses, inadequate attention to scale, and a miring rather than galvanizing of ecological discussions. An additional hindrance to progress may be that investigations tend to focus on processes within either savannas or grasslands, while ignoring the boundary between the two. We propose a new scientific framework for identifying determinants of savanna and grassland distribution, which advocates (a) the recognition of ecosystems and biomes as complex adaptive systems, (b) a scientific methodology based on adaptive inference, and (c) explicit consideration of patch boundaries at various scales. Analysis of processes operating at dynamic savanna–grassland boundaries should permit better separation of ultimate from proximate factors controlling grass–tree interactions within the individual biomes. The proposed savanna–grassland framework has potential for application in other areas of ecology facing similar problems.