|Title||The vertebral formula of the last common ancestor of African apes and humans|
|Publication Type||Journal Article|
|Year of Publication||2010|
|Authors||McCollum, MA, Rosenman, BA, Suwa, G, Meindl, RS, Lovejoy, OC|
|Journal||Journal of Experimental Zoology Part B: Molecular and Developmental Evolution|
|Pagination||123 - 134|
|Keywords||anatomy, bonobos, chimpanzees, homology, miocene apes, vertebrae|
The modal number of lumbar vertebrae in modern humans is five. It varies between three and four in extant African apes (mean=3.5). Because both chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla) possess the same distributions of thoracic, lumbar, and sacral vertebrae, it has been assumed from parsimony that the last common ancestor (LCA) of African apes and humans possessed a similarly short lower back. This “short-backed LCA” scenario has recently been viewed favorably in an analysis of the intra- and interspecific variation in axial formulas observed among African apes and humans (Pilbeam, 2004. J Exp Zool 302B:241–267). However, the number of bonobo (Pan paniscus) specimens in that study was small (N=17). Here we reconsider vertebral type and number in the LCA in light of an expanded P. paniscus sample as well as evidence provided by the human fossil record. The precaudal (pre-coccygeal) axial column of bonobos differs from those of chimpanzees and gorillas in displaying one additional vertebra as well as significantly different combinations of sacral, lumbar, and thoracic vertebrae. These findings, along with the six-segmented lumbar column of early Australopithecus and early Homo, suggest that the LCA possessed a long axial column and long lumbar spine and that reduction in the lumbar column occurred independently in humans and in each ape clade, and continued after separation of the two species of Pan as well. Such an explanation is strongly congruent with additional details of lumbar column reduction and lower back stabilization in African apes. J. Exp. Zool. (Mol. Dev. Evol.) 314B:123–134, 2010.
|Short Title||J. Exp. Zool.|
The vertebral formula of the last common ancestor of African apes and humans
For years, I've worked on their bones. Now I'm working on their genes. Read more about the science studying these ancient people.
From a finger bone of an ancient human came the record of a completely unexpected population. My lab is working on the science of the Denisova genome.
The advent of agriculture caused natural selection to speed up greatly in humans. We're uncovering some of the ways that populations have rapidly changed during the last 10,000 years.