Selection pressures are the factors that lead to evolution by contributing to the selection of variations that provide an individual with an increased chance of surviving over others. Survival includes surviving all threats, whether competitive, natural or from predators. Variations are those attributes or capabilities that distinguish an individual from other types. In the burgeoning new domain of urban air mobility, there are already powerful selection pressures at work. This presentation will identify what those pressures are and their effects in determining which among the more than 170 new aircraft types will sustainably succeed in future implementations of UAM. Included will be a discussion of who or what will act as predators and which aircraft will be their prey.