Biology's First Law The Tendency for Diversity and Complexity to Increase in Evolutionary Systems
by Daniel W. McShea and Robert N. Brandon
University of Chicago Press, 2010
Cloth: 978-0-226-56225-4 | Paper: 978-0-226-56226-1 | Electronic: 978-0-226-56227-8
DOI: 10.7208/chicago/9780226562278.001.0001


Life on earth is characterized by three striking phenomena that demand explanation: adaptation—the marvelous fit between organism and environment; diversity—the great variety of organisms; and complexity—the enormous intricacy of their internal structure. Natural selection explains adaptation. But what explains diversity and complexity? Daniel W. McShea and Robert N. Brandon argue that there exists in evolution a spontaneous tendency toward increased diversity and complexity, one that acts whether natural selection is present or not. They call this tendency a biological law—the Zero-Force Evolutionary Law, or ZFEL. This law unifies the principles and data of biology under a single framework and invites a reconceptualization of the field of the same sort that Newton’s First Law brought to physics.


Biology’s First Law shows how the ZFEL can be applied to the study of diversity and complexity and examines its wider implications for biology. Intended for evolutionary biologists, paleontologists, and other scientists studying complex systems, and written in a concise and engaging format that speaks to students and interdisciplinary practitioners alike, this book will also find an appreciative audience in the philosophy of science.


Daniel W. McShea is Associate Professor of Biology, with a secondary appointment in Philosophy, and Robert N. Brandon is Professor of Philosophy, with a secondary appointment in Biology, both at Duke University.


“The ZFEL will be obvious to some, heretical to others, so the book will be controversial. But at the same time, the argument is rich enough to convince a skeptic, provided that skeptic is open-minded. A novel contribution of far-reaching importance in evolutionary biology.”

— Michael Foote, University of Chicago

Biology's First Law is an original and unusual book. A hybrid of theoretical biology and philosophy of science, it addresses both conceptual and empirical problems…a thought-provoking study.”—Nature

— Samir Okasha, Nature

“[T]his slim book is a great read, putting forth an intuitive and elegant case with significant implications that shed new light on all aspects of biology. It should be read by anyone interested in ecology and evolution and their manifestations across any scale of organismal complexity, from molecules and genes to communities and clades. In other words, every biologist should read it! But it should also be read by physicists, chemists and other reductionists, who might better appreciate the unique roles of biological variability and inheritance that makes our science more complicated, more historicist by nature, more hierarchically emergent, and ultimately innately worthwhile of study.”
— Phil Novack-Gottshall, Priscum




1. The Zero-Force Evolutionary Law

2. Randomness, Hierarchy, and Constraint

3. Diversity

4. Complexity

5. Evidence, Predictions, and Tests

6. Philosophical Foundations

7. Implications