Axial Character Seriation in Mammals

Abstract

Modern biology is increasingly focused on the role of repetitive anatomical structures in the embryological construction of organisms. The discovery of the homeobox (Hox) genes by Edward Lewis in 1978 ushered in a series of stunning revelations such as the fundamental commonality of insect segments and mammalian vertebrae – a wild and ridiculed idea first proposed by Etienne Geoffroy Saint-Hilaire in 1822 that has now been proven correct.

Axial Character Seriation in Mammals is an unabridged edition of the 1986 Harvard University PhD Thesis of Aaron G. Filler, MD, PhD that pioneered our modern reassessment of mammalian vertebrae in the light of the new homeotic biology. As Dr. Filler points out in fascinating detail, the leading explanations of similarity among animals before Darwin were arrayed around the vertebrae of the spine in works by Sir Richard Owen, Johann Wolfgang Goethe and Geoffroy Saint-Hilaire. This was the theoretical structure that was overturned and demolished by Darwin’s ideas about similarity due to common descent. In a stunning reversal, modern homeotic genetics has shown that repeating structures are indeed critical to understanding animal similarity.

This work is the first study of the modern era that views vertebrae as a key to unlocking the way in which Nature has organized repeating biological structures. For the 150 years since the Great Academy Debate of 1830 appeared to demolish Geoffroy Saint-Hilaire’s ideas, vertebrae have been seen as no more than some bones in Vertebrate animals that are involved in support and locomotion. Axial Character Seriation in Mammals, however, explores the fascinating traces of how the morphogenetic genes sculpt and organize serially repeating structures, thus re-establishing the vertebrae as a legitimate and compelling subject of modern science.

In addition to its theoretical perspective, this work provides a mass of previously unknown or inaccessible detail about the fundamentals of vertebral anatomy in mammals. Tracing the evolution, embryology, and function of the various aspects of the vertebrae allows Filler to explore and identify the interwoven roles of morphologic history, developmental programming, and natural selection in molding and diversifying the mammalian spine.

A revised and updated nomenclature for spinal anatomical elements is presented that allows for a uniform naming scheme of all of the features of mammalian vertebrae. Filler identifies a neomorphic structure that emerges at the dawn of mammalian evolution called the laminapophysis that lifts the muscle attachments away from the rib attachments, thereby enabling more efficient respiration during locomotion. In marsupial and placental mammals, the neomorphic laminapophysis undergoes “splitting” at the thoraco-lumbar transition leading to a variety of complex serially descendant structures in the lumbar region such as the mammilary process and the styloid process.

Most remarkably, Filler shows how this 100 million year old process was dramatically altered in the course of the early evolution of the hominoid apes. Presenting historical, anatomical, embryological and paleontological evidence in support, the case is made that human evolution commenced its progress towards the differentiation between ape and human as a consequence of a reconfiguration of the splitting of the laminapophyis. One major functional consequence of the reconfiguration was a lumbar spine uniquely optimized for upright posture and bipedalism. The appearance of the human lumbar design in a Miocene (21 million year old) fossil attributed to the hominoid ape Proconsul major suggests that the upright posture and bipedalism demonstrated by many existing apes and evidenced by a number of fossil apes all shares a common origin and underlying structural basis.

The transformation of the human vertebral architecture is set against the vital context of a detailed anatomical assessment of scores of different vertebral architectures that have appeared among the various mammalian lineages. A stunning set of 108 illustrations including 36 fascinating stereo pair images provide the reader with an unparalleled resource in the exploration of this amazing new world of interaction between the morphogenetics of the Evo-Devo school of thought and the systematics and functional anatomy that have provided theoretical structure in this area in the past.

Finally, exploring conflicts among the various types of homology in identifying elements of vertebral anatomy, Filler questions some of the fundamental bases of the very concept of homology itself. Collectively, this work is a landmark treatise in its field that has been widely referenced by many researchers in the twenty years since it was first written. This new BrownWalker edition finally makes the work widely available along with the paperback’s black and white stereo pairs and an eBook version with red-blue anagram images that both present the spectacular photography in its original striking quality and detail.

About the Author

Aaron Filler is one of the world's leading experts in nerve and spinal diagnostics and surgery. A Medical Director at the Cedars Sinai Institute for Spinal Disorders, he pioneered the field of MR nerve imaging or MR Neurography and advanced MRI guided surgei He has numerous patents and publications in a variety of medical and biological fields. He is the author of Do You Really Need Back Surgery from Oxford University Press.