Max Delbrück Prize in Biological Physics Talk: Precision and emergence in the physics of biological function

Life is more than the sum of its parts: functions crucial for life emerge from interactions among hundreds or thousands of microscopic components. Less obvious, perhaps, is that the mechanisms of life are extraordinarily precise: our visual system counts single photons, many signaling systems are limited by the random arrivals of individual molecules, and more. Observations of extreme precision suggest a theoretical framework in which biological systems have been exquisitely tuned, optimizing performance in the presence of physical constraints. Observations of emergence suggest a different theoretical framework, in which functional behaviors are collective, and hence perhaps insensitive to microscopic details. I will give examples of both approaches, in systems ranging from a developing embryo to large networks of neurons, and from computation in the visual system to flocks of birds. At the end I will try to reconcile the two points of view. I hope to make clear why I believe that a more unified, and unifying, theoretical physics of biological systems is within reach.