I. Many believe that sooner or later molecular biology will mechanistically provide the precise genotypic basis for phenotypic change. This in turn will provide the basis for attacking several major evolutionary problems posed by paleontology, including the following:
— There are approximately 30 phylum-level taxa in the animal kingdom, and yet in the “fast” version of evolutionary history, many of then arose 600 Myr ago in a very short period of time (of order <30 Myr). In terms of basic body plan and inferred ecology, these sponges, clams, arthropods, etc. were seemingly as different then as they are now. It is as though the rate of morphologic change was much more rapid during that interval than during the nearly 600 Myr since then. Even the “slow” version of evolutionary history (which allows for an additional unfossilized record of about 500 Myr) demands an answer to what has controlled the development of major evolutionary Bauplans.
— Some morphologic traits (though probably not individual species) persist for immense periods of geologic time—the general shape of the horseshoe crab, for example, or the bristle patterns of taxa of meiofaunal “worms” living among sand grains. What is the developmental rationale for these persistent traits? In short, what is the molecular basis for genetic and morphologic canalization?
— The general pattern of species specialization proceeds unabated overtime, but every once in a while the developmental clock is reset. Organisms which are sexually mature but with simplified or “primitive” morphology arise de novo, and these lineages then form the stock of unspecialized forms from which future specializations evolve. What is the molecular basis for resetting the developmental clock?
— Reproductive isolation may arise “accidentally” through genomic changes unrelated to changes in the local environment. To the extent this is true, speciation has a largely accidental component. Knowledge of the rate and type of genomic change is critical for an evaluation of this idea.
