"We applaud the burgeoning emphasis on change in regulatory genes as the stuff of morphological evolution... if only because one of us had written a book to argue that the classical, and widely ignored data on evolution by heterochrony should be exhumed and valued as a primary demonstration of regulatory change. We do not see how point mutations in structural genes can lead, even by gradual accumulations, to new morphological designs. Regulatory changes in the timing of complex ontogenetic programs seem far more promising—and potentially rapid, in conformity with our punctuational predilections. The near identity of humans and chimps for structural genes, and the evidence of major regulatory change indicated by human neoteny provides an important confirmation."