AXIAL CHARACTER SERIATION IN MAMMALS: AN HISTORICAL AND MORPHOLOGICAL EXPLORATION OF THE ORIGIN, DEVELOPMENT, USE, AND CURRENT COLLAPSE OF THE HOMOLOGY PARADIGM (VERTEBRAE, LOCOMOTION, HOMEOTIC, EVOLUTION, HOMINOID)

The immediate impact of Darwinian theory for nineteenth century morphologists was to assert that the explanatory key to organismal biology lay in common ancestry rather than in repetition of axial structures. This revolution lent the appearance of biological validity to special homology between organisms, but demoted serial homology from its central theoretical position to a place as an unwanted and discarded relict of pre-Darwinian thought. In consequence, not only was this category of homology neglected, but the study of axial structures themselves was effectively abandoned.;Principal morphologic findings are: (1) Much of the unique vertebral anatomy of various mammals groups is due to serial modification of a previously unrecognized neomorph, and laminapophysis, which first appears in some therapsids and defines a clade including all mammals. (2) The serial homology of the lumbar transverse process varies, and in some hominoids it is with a derivative of the laminapophysis, not the rib. The consequences of this morphology includes impressive evidence that the common ancestor of chimpanzees and humans was an upright biped. (3) "Resegmentation" appears to occur variably. (4) Several mammalian groups display structures that may be equivalent with the homeotic mutants used in the genetic dissection of Drosophila morphogenesis.;At a theoretical level, the data confirm an old example of contradiction between serial and special homology and identify numerious additional examples. "Field homology" by hierarchical dominance of morphogenetic influence is proposed to account for some of these. However, the collective import of the data show that the homology paradigm in general is based on a misconceived expectation of Platonic typology. Homology is a practical formalism, not a biological phenomenon.;Discovery of a serial relation in the mammalian axial skeleton by Goethe in 1790 launched much of the morphological program which continues to this day. A return to the study of mammalian axial anatomy 196 years after that seminal event and 127 years after the Darwinian devastation of this field new reveals a wealth of specific and generalizable morphologic and theoretical information.