The first rib of hominoids

Bibliographic Data

ID8316482
AuthorsJames C Ohman (0000-0002-3789-3469, Ohio University, corresponding author)
Year1986
Volume70
Issue2
Pages209-229
Publication date1986-06-01
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueAmerican Journal of Physical Anthropology (JOURNAL)
Journal identifiersISSN: 0002-9483 • E-ISSN: 1096-8644
PublisherWiley (PUBLISHER • GB)
DOI10.1002/ajpa.1330700208
PMID3090892
OpenAlexW2040872382
LanguageEN
Citations received26
References cited44

Homo sapiens is unique among extant hominoids in displaying a univertebral articular pattern for the first rib; that is, the head of the first rib articulates only with the body of the first thoracic vertebra. All other hominoids, indeed virtually all other mammals, display a bivertebral pattern; that is, the head of the first rib articulates with the bodies of both the seventh cervical and the first thoracic vertebrae, as well as the intervening disk. Two fossil hominid partial first ribs, A.L. 288‐lax and A.L. 333‐118, show that the univertebral pattern was fully established in the hominid lineage by the appearance of Australopithecus afarensis . Four hypotheses, based in functional anatomy, can be postulated for the evolution of the univertebral pattern: (1), it increases the volume (via increased length) of the neck, which could, in turn, compensate for the functional loss of the laryngeal sac systems in hominid vocalization; (2), it is a consequence of the more barrel‐shaped thorax in hominids; (3), it is a consequence of functional modifications in the hominid shoulder girdle; and/or (4), it is a consequence of modifications in hominid first rib motion while breathing in an upright stance. Fossil evidence supports all but the first hypothesis, and most strongly supports the third. However, evidence for the first hypothesis does suggest that the evolution of descent of the upper respiratory system in the hominid lineage may have been permitted by the presence of the univertebral pattern, while the reverse is probably not true. Furthermore, fossil evidence for the third hypothesis shows that, by the appearance of A. afarensis , the hominid upper limb had been freed from locomotor constraints, which concomitantly confirms full adaptation to upright posture. Thus, because of their potential relationship with upright posture, the two remaining hypotheses (i.e., “thoracic shape” and “first rib movement during breathing”) also have support from the fossil evidence

Archaeology · Australopithecus · Biological evolution · Biology · Bipedalism · Cervical vertebrae · Evolutionary biology · Extant taxon · Fossil Record · Hominidae · Homo sapiens · Human evolution · Lineage (genetic · Osteology · Pectoral girdle · Rib cage · Thorax (insect anatomy · Anatomy · Evolution and Paleontology Studies · Geology and Paleoclimatology Research · Paleontology · Pleistocene-Era Hominins and Archaeology

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