In fact, our present understanding of morphogenesis indicates that new phyla were not made by new genes but largely emerged through
the rewiring of the gene regulatory networks (GRNs) of already existing genes (1).
Marshall points out that the relatively fast appearance
of new animal species in this period is not driven by new
genes, but rather by evolving from existing
genes through «
rewiring»
of the
gene regulatory networks (GRNs).