The Horn of Africa and Southwest Arabia are less than 30 km apart, yet the timing and nature of transitions to agriculture along the margins of the southern Red Sea differ substantially. This paper compares and contrasts the beginnings of agriculture in highland Ethiopia/Eritrea and Yemen. We evaluate the applicability of general models, emphasize social circumstances and particularities, and highlight the importance of differing spatiotemporal scales from interregional perspectives that address millennia-long changes across continents to local choices during human lifetimes. We consider why agriculture appears so much later than it does throughout the eastern Mediterranean and argue that the traditionally rigid distinction between the "origins" and "spread" of agriculture oversimplifies transitions along the southern Red Sea in which agriculture in some ways diffused to, and in other ways, uniquely originated in Southwest Arabia and the Horn of Africa. We concordantly maintain that, particularly when agriculture is considered a societal transformation, regions where agriculture appears comparatively later are as important to understanding transitions to agriculture as regions where agriculture appears earliest.