SEARCHING FOR THE MOLECULAR BASIS OF PUNCTUATED EQUILIBRIA (Invited Presentation)

Eldredge and Gould (1972) predicted the existence of a “powerful homeostatic system” that allows species to maintain relative stasis for long periods of time (pp. 114). At the time, however, with the genetics revolution still in its infancy and sequencing of the human and other genomes decades away, attention turned to the abiotic environment as a primary means of explanation. While it is clear that the physical environment plays a dramatic role in both species stasis and punctuated speciation events, the question remains whether there is a complementary internal homeostatic system that acts as a buffer to morphological change. Casanova and Konkel (2020) proposed The Developmental Gene Hypothesis of Punctuated Equilibria—highlighting a molecular mechanism that, with further research, appears to act as a buffer or anchor to such change. Developmental regulatory (DevReg) genes, which play orchestral roles in tissue morphology, including skeletal morphology, are proposed as a major driver in Punctuated Equilibria. We will provide new evidence that these genes are strongly conserved across Metazoa, despite that other aspects of genome evolution are highly variable across phyla. Instead, DevReg genes appear to form a metazoan gene core. In addition, we will also provide evidence that these genes are directly implicated in bone morphogenesis. Because the skeletal form is better represented in the fossil record than soft tissues, the molecular mechanisms regulating its development are highly relevant to the theory of Punctuated Equilibria as it relates to vertebrates. We will further discuss evidence of historically contingent genomic events, such as whole genome duplications and transposable element radiations, which appear to be key players in major speciation events. Together, DevReg gene conservation and the occurrence of historically contingent molecular events form the basis for The Developmental Gene Hypothesis and provide avenues for revitalization of investigational research into Punctuated Equilibria from the molecular perspective.