The Upright Ape: A New Origin of the Species

by Aaron G. Filler, MD, PhD

Figure 9-2 Transformation of the Primate Lumbar Spine Into the Human Form

Comparative anatomy of lumbar vertebrae in humans and other primates

Figure 9-2 - Critical human feature: unique lumbar transverse process and styloid loss.

A – The LTP (lumbar transverse process) in humans differs tremendously from related primates. It is dorsal to the position of the spinal canal. It is thick and strong instead of flat and thin.

B,C - Styloid comparison. Lateral view of lumbar vertebrae of human, macaque monkey and Proconsul africanus. The human vertebra, like Morotopithecus, appears to demonstrate absence of the styloid process and relocation of the LTP onto the arch of the vertebra at the base of the structure that carries the facet joint. (D) Proconsul africanus appears to have the more primitive LTP and styloid seen in monkeys and most other mammals.

Figure credit -

From: Filler, A. G. (2007a). Homeotic evolution in the Mammalia: Diversification of therian axial seriation and the morphogenetic basis of human origins. (forthcoming).

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