In physical anthropology, post-orbital constriction is the narrowing of the cranium (skull) just behind the eye sockets (the orbits, hence the name) found in most non-human primates and early hominins. This constriction is very noticeable in non-human primates, slightly less so in Australopithecines, even less in Homo erectus and completely disappears in modern Homo sapiens.[1] Post-orbital constriction index in non-human primates and hominin range in category from increased constriction, intermediate, reduced constriction and disappearance.[1] The post-orbital constriction index is defined by either a ratio of minimum frontal breadth (MFB), behind the supraorbital torus, divided by the maximum upper facial breadth (BFM), bifrontomalare temporale, or as the maximum width behind the orbit of the skull.[1][2][3]
Top view of Australopithecus africanus skull with post-orbital constriction (left) and modern human skull without (right)
Measurement of cranial capacity in hominis has been long used to examine the evolutionary development of increased brain size, allowing for comparing and contrasting among hominin skulls and between primates and hominins. Similarly, the post-orbital constriction index has become a form to compare and contrast craniums with the possibility of determining the relative age and evolutionary place of a new found hominin. Cranial capacity and post-orbital constriction index can demonstrate a correlation between increased brain size and reduced post-orbital constriction.[4] For example, the average cranial capacity for Australopithecines is 440 cc, and the post-orbital constriction index is 0.66.[1][5] However, with the evolutionary change in brain size in Australopithecines to the Homo genus, the average cranial capacity for Homo Habilis is 640 cc, and the post-orbital constriction index is 0.72.[1][5] More specifically, in a departure from Homo erectus, Homo sapiens manifests a absolutely reduced post-orbital constriction (post-orbital constriction disappears) and a post-orbital constriction index of 0.92 due to increase in cranial capacity, about 1,350 cc.[1][6] From the Australopithecines to the Homo genus, along with an increase in cranial capacity, a transition from intermediate constriction to reduced constriction is visible, and eventually disappearance. Brain growth has changed both the appearance of the sagittal crest and post-orbital constriction.[4] KNM-ER 406, the skull of a Paranthropus, brain volume estimated to 410 cm3 with a visible sagittal crest and mild or intermediate post-orbital constriction but KNM-ER 37333, the skull of a Homo erectus, brain volume of 850 cm3 with no visual sagittal crest and an almost not present or reduced post-orbital constriction.[4]
Minatogawa I and IV and Dali
Minatogawa I-IV cranium were discovered in Okinawa Island in 1970-1971.[7] The skulls and other fossils found associated were dated to be 150,000-200,00 years old, with a chance of being slightly older.[7] In a study led by Daisuke Kubo, Reiko T. Kono, and Gen Suwa, the craniums for Minatogawa I and IV were further examined to identify cranial capacity and concluded that Minatogawa I's estimated cranial size is 1335 cc and Minatogawa IV's is 1170 cc,[7] very close to the average cranial size of modern Homo sapiens. Kubo, et al. identify two possible forms of measuring post-orbital constriction, established by measuring the anterior, closer to the face, and posterior of the cranium.[7] Researchers conclude that both cranium demonstrate a marked or almost reduced post-orbital constriction in both measurements of post-orbital constriction, compared to modern Homo sapiens.[7]
The Dali cranium was discovered in 1978 in Dali County, Shaanxi.[8] The cranium is described to be large with some robust features similar to early Western Homo sapiens and noticeable differentiation from the cranium of Homo erectus found in Zhoukoudian.[8] The Dali cranium was found to exhibit a pronounced or almost reduced post-orbital constriction with a post-orbital constriction index of 0.85,[8] much stronger than primates and early hominin and falling fairly close to the post-orbital constriction index of Homo sapiens. The Dali cranium is an example of the evolutionary development of post-orbital constriction as brain size enlarges and develops similar features found in modern Homo sapiens.
Temporalis Muscle
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.[7] As such, the anterior and posterior portions of the anterior temporalis muscle are inversely correlated in size, with the anterior being larger.[7] 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.[9]
^ abcdefgCameron, David W. (2004). Bones, stones, and molecules : "out of Africa" and human origins. Groves, Colin P. Burlington, MA: Elsevier Academic Press. ISBN978-0-12-156933-4. OCLC 162571244.
^Monson, Ta; Brasil, Mf; Stratford, Dj; Hlusko, Lj (2017). "Patterns of craniofacial variation and taxonomic diversity in the South African Cercopithecidae fossil record". Palaeontologia Electronica. doi:10.26879/690. ISSN 1094-8074.
^Kimbel, William H.; White, Tim D.; Johanson, Donald C. (August 1984). "Cranial morphology ofAustralopithecus afarensis: A comparative study based on a composite reconstruction of the adult skull". American Journal of Physical Anthropology. 64 (4): 337–388. doi:10.1002/ajpa.1330640403. ISSN 0002-9483. PMID 6435455.
^ abcGamble, Clive (2014). Settling the Earth: The Archeology of Deep Human History. New York: Cambridge Univ. Press. pp. 148–151.
^"Archaic Homo sapiens | Learn Science at Scitable". www.nature.com. Retrieved 2020-05-23.
^ abcdefgKUBO, 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.
^ abcRukang, Wu (2016-09-16). Rukang, Wu; Olsen, John W (eds.). Paleoanthropology and Paleolithic Archaeology in the People's Republic of China. doi:10.4324/9781315423135. ISBN9781315423135.
^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. doi:10.1127/zma/80/1994/51. JSTOR 25757416.
January 13, 2023
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In physical anthropology post orbital constriction is the narrowing of the cranium skull just behind the eye sockets the orbits hence the name found in most non human primates and early hominins This constriction is very noticeable in non human primates slightly less so in Australopithecines even less in Homo erectus and completely disappears in modern Homo sapiens 1 Post orbital constriction index in non human primates and hominin range in category from increased constriction intermediate reduced constriction and disappearance 1 The post orbital constriction index is defined by either a ratio of minimum frontal breadth MFB behind the supraorbital torus divided by the maximum upper facial breadth BFM bifrontomalare temporale or as the maximum width behind the orbit of the skull 1 2 3 Top view of Australopithecus africanus skull with post orbital constriction left and modern human skull without right Contents 1 Cranial Evolution 2 Minatogawa I and IV and Dali 3 Temporalis Muscle 4 See also 5 ReferencesCranial Evolution EditPost orbital constriction for various hominids 1 Increased constrictionGorilla 0 57P aethiopicus KNM WT 17000 0 57P boisei KNM ER 406 0 57IntermediateDryopithecus RUD 77 0 73Sahelanthropus TM 266 01 060 1 0 59Australopithecus 0 66P robustus 0 70Homo habilis OH 24 KNM ER 1813 0 72H rudolfensis 0 70H ergaster 0 75Pongo 0 66Pan 0 70Reduced constrictionPraeanthropus 0 80Absolutely reduced constrictionHomo sapiens 0 92Measurement of cranial capacity in hominis has been long used to examine the evolutionary development of increased brain size allowing for comparing and contrasting among hominin skulls and between primates and hominins Similarly the post orbital constriction index has become a form to compare and contrast craniums with the possibility of determining the relative age and evolutionary place of a new found hominin Cranial capacity and post orbital constriction index can demonstrate a correlation between increased brain size and reduced post orbital constriction 4 For example the average cranial capacity for Australopithecines is 440 cc and the post orbital constriction index is 0 66 1 5 However with the evolutionary change in brain size in Australopithecines to the Homo genus the average cranial capacity for Homo Habilis is 640 cc and the post orbital constriction index is 0 72 1 5 More specifically in a departure from Homo erectus Homo sapiens manifests a absolutely reduced post orbital constriction post orbital constriction disappears and a post orbital constriction index of 0 92 due to increase in cranial capacity about 1 350 cc 1 6 From the Australopithecines to the Homo genus along with an increase in cranial capacity a transition from intermediate constriction to reduced constriction is visible and eventually disappearance Brain growth has changed both the appearance of the sagittal crest and post orbital constriction 4 KNM ER 406 the skull of a Paranthropus brain volume estimated to 410 cm3 with a visible sagittal crest and mild or intermediate post orbital constriction but KNM ER 37333 the skull of a Homo erectus brain volume of 850 cm3 with no visual sagittal crest and an almost not present or reduced post orbital constriction 4 Minatogawa I and IV and Dali EditMinatogawa I IV cranium were discovered in Okinawa Island in 1970 1971 7 The skulls and other fossils found associated were dated to be 150 000 200 00 years old with a chance of being slightly older 7 In a study led by Daisuke Kubo Reiko T Kono and Gen Suwa the craniums for Minatogawa I and IV were further examined to identify cranial capacity and concluded that Minatogawa I s estimated cranial size is 1335 cc and Minatogawa IV s is 1170 cc 7 very close to the average cranial size of modern Homo sapiens Kubo et al identify two possible forms of measuring post orbital constriction established by measuring the anterior closer to the face and posterior of the cranium 7 Researchers conclude that both cranium demonstrate a marked or almost reduced post orbital constriction in both measurements of post orbital constriction compared to modern Homo sapiens 7 The Dali cranium was discovered in 1978 in Dali County Shaanxi 8 The cranium is described to be large with some robust features similar to early Western Homo sapiens and noticeable differentiation from the cranium of Homo erectus found in Zhoukoudian 8 The Dali cranium was found to exhibit a pronounced or almost reduced post orbital constriction with a post orbital constriction index of 0 85 8 much stronger than primates and early hominin and falling fairly close to the post orbital constriction index of Homo sapiens The Dali cranium is an example of the evolutionary development of post orbital constriction as brain size enlarges and develops similar features found in modern Homo sapiens Temporalis Muscle EditIn 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 7 As such the anterior and posterior portions of the anterior temporalis muscle are inversely correlated in size with the anterior being larger 7 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 9 See also EditAlveolar prognathism CraniometryReferences Edit a b c d e f g Cameron David W 2004 Bones stones and molecules out of Africa and human origins Groves Colin P Burlington MA Elsevier Academic Press ISBN 978 0 12 156933 4 OCLC 162571244 Monson Ta Brasil Mf Stratford Dj Hlusko Lj 2017 Patterns of craniofacial variation and taxonomic diversity in the South African Cercopithecidae fossil record Palaeontologia Electronica doi 10 26879 690 ISSN 1094 8074 Kimbel William H White Tim D Johanson Donald C August 1984 Cranial morphology ofAustralopithecus afarensis A comparative study based on a composite reconstruction of the adult skull American Journal of Physical Anthropology 64 4 337 388 doi 10 1002 ajpa 1330640403 ISSN 0002 9483 PMID 6435455 a b c Gamble Clive 2014 Settling the Earth The Archeology of Deep Human History New York Cambridge Univ Press pp 148 151 a b Human evolution Increasing brain size Encyclopedia Britannica Retrieved 2020 05 23 Archaic Homo sapiens Learn Science at Scitable www nature com Retrieved 2020 05 23 a b c d e f g 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 a b c Rukang Wu 2016 09 16 Rukang Wu Olsen John W eds Paleoanthropology and Paleolithic Archaeology in the People s Republic of China doi 10 4324 9781315423135 ISBN 9781315423135 Picq Pascal 1994 Craniofacial size and proportions and the functional significance of the supraorbital region in primates Zeitschrift fur Morphologie und Anthropologie 80 1 51 63 doi 10 1127 zma 80 1994 51 JSTOR 25757416 Retrieved from https en wikipedia org w index php title Post orbital constriction amp oldid 1131298594, wikipedia, wiki, book, books, library,
