According to activity systems theory, continuous optimization of an activity system can lead an organization to such a tight internal fit that it becomes difficult for it to adapt to external changes. Prior activity systems research has not, however, considered the role of acquisitions in alleviating such activity system rigidity and enabling continuous adaptation. Based on a comparative case analysis of the longitudinal evolution of Alphabet and Amazon, both active serial acquirers, we identify multiple ways in which acquisitions contributed to the evolution of their activity systems by both enhancing existing activity system elements ("thickening") and introducing new ones ("patching"). Counterintuitively, we find that while both companies used acquisitions for thickening and patching in multiple different ways, the more incremental overall evolutionary pathway adopted by Amazon resulted in a more significant renewal of its activity system over time than the more radical approach adopted by Alphabet. It would seem that the more radical acquisitions, despite having more potential for renewal, were too far from the existing activity system to complement its elements and renew the activity system as a whole. Moreover, contrary to prior research that tends to implicitly assume that organizations adapt their activity systems mainly as a response to exogenous environmental changes, we find that both companies were continuously proactively developing their activity systems. Acquisitions provide for these companies, in this respect, invaluable cognitive means to recognize different potential alternatives for proactive activity systems renewal.
