--- - |2 Abstract In the fields of linguistics and cognitive science, considerable attention has been devoted to the question of how linguistic structure emerged over evolutionary time. Here, we highlight the contribution of a fundamental constraint on processing, the Now‐or‐Never bottleneck. Language takes place in the here and now, with the transience of acoustic speech signals and our exceedingly limited memory for sound sequences requiring immediate processing. To overcome this bottleneck, the cognitive system employs basic chunking mechanisms to rapidly compress and recode incoming linguistic input into increasingly abstract levels of representation, thereby prolonging its retention in memory. Our suggestion is that these chunk‐based memory processes influence linguistic structure across multiple time scales. Chunk‐based memory constraints govern language acquisition and processing on the level of the individual. Through usage, linguistic structures that are more easily chunked will tend to proliferate, thus shaping the cultural evolution of language across generations of language users. This results in a selection of learnable structures, from individual words to multiword sequences that are optimally “chunkable,” so as to better squeeze through the Now‐or‐Never bottleneck. From this perspective, language can be thought of as an adaptive system that culturally evolves to fit learners’ cognitive capabilities, thereby resulting in the structure it bears today. - Topics in Cognitive Science, EarlyView.