 The idea that evolution constitutes changing developmental relationships is central for the field of evolutionary developmental biology (evo-devo). The field describes itself as the science that studies how alterations in development create the variations that nature can select (Raff &amp; Kaufman 1983; Gilbert, Opitz, &amp; Raff 1996). In other words, natural selection did not create variation; development creates variation. Development is the artist; natural selection is the curator (Gilbert 2006, 2019). Both have creative agency; but they are working at different levels. Although this view had been expressed by scientists such as Thomas Huxley, Julian Huxley, Conrad H. Waddington, and Richard B. Goldschmidt, it gained credence through more recent discoveries that explained how normal development could occur. Chief among these discoveries was the explication of developmental pathways that connected embryonic induction with gene expression. Here, paracrine factors (proteins that influence the behaviors or gene expression patterns of neighboring cells) secreted by one set of cells were received by receptors on the membranes of other cells. These receptors then activated proteins within the cytoplasm, which eventually activated or repressed proteins that entered the nucleus to regulate transcription of particular genes.