Post-orbital constriction
| Increased constriction | |
|---|---|
| Gorilla | 0.57 |
P. walkeri (KNM-WT 17000) | 0.57 |
P. boisei (KNM-ER 406) | 0.57 |
| Intermediate | |
Dryopithecus (RUD 77) | 0.73 |
Sahelanthropus (TM 266-01-060-1) | 0.59 |
| Australopithecus | 0.66 |
| P. robustus | 0.70 |
Homo habilis (OH 24, KNM-ER 1813) | 0.72 |
| K. rudolfensis | 0.70 |
| H. ergaster | 0.75 |
| Pongo | 0.66 |
| Pan | 0.70 |
| Reduced constriction | |
| Praeanthropus | 0.80 |
| Absolutely reduced constriction | |
| Homo sapiens | 0.92 |
In physical anthropology, post-orbital constriction, often referred to as the post-orbital constriction index, is a narrowing of the cranium (skull) just behind the eye sockets (the orbits, hence the name), in primates — including primitive hominids. This constriction is very noticeable in non-human primates, slightly less so in Australopithecines, even less in Homo erectus and the most primitive Homo sapiens.[1] The post-orbital constriction index of archaic Homo species begins to fall within the range of modern Homo sapiens during the Mid-Pleistocene era.[2] In a departure from Homo erectus, Homo sapiens manifests a reduced post-orbital constriction due to increase in cranial capacity (about 1,350 cc), accompanied by higher cranial vaults. It completely disappears in modern Homo sapiens.[3] Thus, it is a useful, quantifiable measure of how far along the evolutionary path a hominid fossil might be placed.
In species such as baboons and African great apes, an increase in the available capacity of the infratemporal fossa is simultaneously accompanied by a constriction in the sagittal plane.[4] As such, the anterior and posterior portions of the anterior temporalis muscle are inversely correlated in size, with the anterior being larger.[4] Although the temporalis muscle is used for chewing, there is no evidence that the supraorbital structure of primates is dependent upon their respective chewing habits or dietary preferences.[5]
Post-orbital constriction is defined by either a ratio of minimum frontal breadth (MFB) behind the supraorbital torus divided by maximum upper facial breadth (bifrontomalare temporale, BFM) or as the maximum width behind the orbit of the skull.[1][6][7]
See also
- Alveolar prognathism
- Craniometry
Notes
^ abc Cameron 2004, pp 304-305
^ Rightmire, G. Philip (2008-02-22). "Homo in the middle pleistocene: Hypodigms, variation, and species recognition". Evolutionary Anthropology: Issues, News, and Reviews. 17 (1): 8–21. doi:10.1002/evan.20160. ISSN 1060-1538..mw-parser-output cite.citationfont-style:inherit.mw-parser-output qquotes:"""""""'""'".mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em
^ "Archaic Homo sapiens | Learn Science at Scitable". www.nature.com. Retrieved 2018-08-09.
^ ab KUBO, DAISUKE; KONO, REIKO T.; SUWA, GEN (2012). "Endocranial proportions and postorbital morphology of the Minatogawa I and IV Late Pleistocene Homo sapiens crania from Okinawa Island, Japan". Anthropological Science. 120 (2): 179–194. doi:10.1537/ase.110804. ISSN 0918-7960.
^ Picq, Pascal (1994). "Craniofacial size and proportions and the functional significance of the supraorbital region in primates". Zeitschrift für Morphologie und Anthropologie. 80 (1): 51–63.
^ Kimbel, William H.; White, Tim D.; Johanson, Donald C. (1984-08). "Cranial morphology ofAustralopithecus afarensis: A comparative study based on a composite reconstruction of the adult skull". American Journal of Physical Anthropology (in French). 64 (4): 337–388. doi:10.1002/ajpa.1330640403. ISSN 0002-9483. Check date values in:|date=(help)
^ Monson, Tesla; F. Brasil, Marianne; J. Stratford, Dominic; Hlusko, Leslea (2017-02-14). "Patterns of craniofacial variation and taxonomic diversity in the South African Cercopithecidae fossil record". Palaeontologia Electronica. 20.1.7A: 1–20. doi:10.26879/690.
References
Cameron, David W.; Groves, Colin P. (2004). Bones, stones, and molecules: "out of Africa" and human origins. Academic Press. ISBN 0-12-156933-0.
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