Applying Life-History Theory to Development: A Two-Tiered Model All Along?

In response to recent arguments for a one-tiered model of life-history development, Ellis and colleagues present a two-tiered model that integrates energetics with development. Early formulations of this model were, however, already two-tiered. The target article separates itself from earlier work by digging deeper into the underlying energetics assumption and how it transacts with ambient cues to impact development.