Answering evolutionary questions: A guide for mechanistic biologists.

The questions and methods of molecular biology and evolutionary biology are clearly distinct, yet a unified approach can lead to deep insights. Unfortunately, attempts to unify these approaches are fraught with pitfalls. In this informal series of questions and answers, we offer the mechanistically oriented biologist a set of steps to come up with evolutionarily reasonable and meaningful hypotheses. We emphasize the critical power and importance of carefully constructed null hypotheses, and we illustrate our ideas with examples representing a range of topics, from the biology of aging, to protein structure, to speciation, and more. We also stress the importance of mathematics as the lingua franca for biologists of all stripes, and encourage mechanistic biologists to seek out quantitative collaborators to build explicit mathematical models, making their assumptions explicit, and their logic clear and testable. Biologists in all realms of inquiry stand to gain from strong bridges between our disciplines.