Bottom-Up of Top-Down?


Dr. Robert F. DeHaan


  There are two logical possibilities of how species and large groups of animals came into being and changed systematically over geologic time. The first is from the bottom up, that is, from multitudes of varieties and species to fewer, higher more general animal forms. The second is from top down, from a few higher, general forms, to innumerable lower, particular species.

The bottom-up perspective is rooted in Darwin's Origin of Species, and has been maintained without exception be all Darwinians, including Simpson, Mary, Eldredge, and Thompson; and in Martin's Dictionary of Life Sciences, and Reese's Encyclopedia of Philosophy. But is it confirmed by the objective evidence? This presentation will review and evaluate data and arguments purporting to confirm the bottom up framework.

The top-down concept will be examined in the light of studies of the Cambrian explosion and subsequent trends in the fossil record, including reports of well-fossilized marine invertebrates, Trilobites, amphibians, reptiles, mammals, birds, and species.

A new theoretical framework, based on principles of development, called macro-development, will be proposed to account for the data from the Cambrian explosion and the fossil record. Sequential and morphological patterns of individual development will be shown to be isomorphic. that is similar, to phyletic trends in the fossil record. Profiles of changes in phyletic lineages match up well with principles of development.

Implications of the new developmental framework for Darwinian theory will be briefly discussed.

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