Arabic historical dialectology has long been based on a historical methodology, one which seeks to link historical population movements with modern linguistic behavior. This article argues that a nexus of interrelated issues, centered around a general theme of “oldness,” has impaired this work, and proposes basic principles to avoid the misinterpretation of linguistic data. This article argues that there is a strong tendency to essentialize the idea of linguistic conservatism and attribute it to the groups that have archaic features. Against this view, it proposes that linguistic conservatism should be seen as a failure to participate in otherwise widespread innovations. It critiques the assumption that the modern dialect distribution is directly derived from the earliest settlements established during the Islamic conquests in the seventh century, arguing instead that long-term linguistic durability is unlikely. The article further challenges the assumption that highly conservative dialects such as those of Yemen are ancestral to modern dialects in a meaningful way, arguing instead that either more proximate ancestors or wave-like diffusion had a greater impact on the development of modern dialects. Finally, the paper suggests that a heuristic approach based on typical processes of language diffusion and human migration offers a more productive approach to understanding the history of Arabic dialects than a model based on historical events; many of the existing linguistic classifications may be directly derived from this heuristic.