This issue contains the inaugural contribution to “Critical Concepts in Biological Theory,” a new feature of the journal. The article, “Serial Homology,”Footnote 1 by the evolutionary developmental biologist Giuseppe Fusco, discusses the history of the concept, its purported place in comparative anatomy and evolutionary theory, and controversies about its applicability in various narrow and broader cases. This was a significant challenge to an author in a format designed to be less than 3000 words. It was therefore gratifying that Professor Fusco was able to deliver a true exemplar of something (a type of article in this case) for which no homolog yet existed, but future ones were anticipated.

The “Critical Concepts” articles will be commissioned in consultation with Biological Theory’s editors by Kenneth McKenna, an integrative biologist with a background in developmental genetics and evolutionary theory. Dr. McKenna put forward the idea for this feature and will serve as the section editor. In his initial proposal he suggested that the brief articles should focus on fundamental concepts in evolutionary, developmental, or cognitive biology, in concisely written perspectives that do not sidestep controversies or disagreements. Where appropriate, the essays will connect theory building to experimental research.

These articles, which will appear intermittently, are intended to be responsive to the extreme specialization in modern scientific work and the search by scholars for entry points into ideas that their colleagues and collaborators in adjacent fields have been discussing, or that students are asking about. While addressed to a sophisticated audience, they will be written with a view toward interdisciplinary comprehension. And although the constraints of the form will inevitably incline to personal perspectives, they will not neglect opposing ones. For these reasons, contributors of “Critical Concepts” pieces will be selected among scientists and philosophers who are simultaneously established and at least a bit contrarian in their respective fields. We are off to a good start.