Analysis of the degree of intraspecific morphological polymorphism during the evolutionary history of trilobites using an informatic approach1 provides striking evidence of a long‐suspected but previously unsubstantiated pattern: degrees of polymorphism are markedly higher in phylogenetically basal, stratigraphically early species. This unequivocal pattern prompts further exploration of the relationship between microevolutionary variance and macroevolutionary history. It demonstrates that the ‘traditional’ fossil record of skeletonized organisms can provide unique insight into questions of major evolutionary interest. BioEssays 29:1081–1084, 2007. © 2007 Wiley (...) Periodicals, Inc. (shrink)