Have We Outgrown the Existing Models of Growth?

Theories of growth have a long history in biology. Two major branches of theory (mechanistic and phenomenological) describe the dynamics of growth and explain variation in the size of organisms. Both theory branches usually assume that reproductive output scales proportionately with body size, in other words that reproductive output is isometric. A meta-analysis of hundreds of marine fishes contradicts this assumption, larger mothers reproduce disproportionately more in 95% of species studied, and patterns in other taxa suggest that reproductive hyperallometry is widespread. We argue here that reproductive hyperallometry represents a profound challenge to mechanistic theories of growth in particular, and that they should be revised accordingly. We suspect that hyperallometric reproduction drives growth trajectories in ways that are largely unanticipated by current theories.