Reply to Zhang et al.: The critical temperature dependence of developmental rates is in search of a mechanism

The observation that the rate of development scales with temperature T as (T−TC) for a broad range of animals is very interesting as it strongly suggests a common mechanism, yet an explanation for it is currently lacking. Zhang et al. (1), in their letter responding to our recent study on developmental timing in Caenorhabditis elegans (2), suggest this temperature dependence is due to development taking place near a critical point, with TC the critical temperature. If correct, it would imply that similar conceptual mechanisms underlie processes as diverse as phase transitions in inanimate matter and development in complex multicellular organisms.