{"id":152,"date":"2017-09-13T20:20:07","date_gmt":"2017-09-13T20:20:07","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-history-of-our-tribe\/chapter\/17-australopithecusparanthropus-aethiopicus\/"},"modified":"2017-10-03T16:08:52","modified_gmt":"2017-10-03T16:08:52","slug":"17-australopithecusparanthropus-aethiopicus","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-history-of-our-tribe\/chapter\/17-australopithecusparanthropus-aethiopicus\/","title":{"raw":"17. Australopithecus\/Paranthropus aethiopicus","rendered":"17. Australopithecus\/Paranthropus aethiopicus"},"content":{"raw":"
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Australopithecus\/Paranthropus aethiopicus <\/i>(2.7\u20132.3 mya)<\/b><\/h1>\r\n

(\u201csouthern ape\u201d \/ \u201cbeside human\u201d \/ Ethiopia)<\/h2>\r\n[caption id=\"attachment_223\" align=\"aligncenter\" width=\"300\"]\"7.38\" Figure 17.1\u00a0<\/em>Model of Paranthropus aethiopicus. \u201cParanthropus aethiopicus<\/a>\u201d by Nrkpan is licensed under CC BY-SA 3.0<\/a>.[\/caption]\r\n\r\n
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SITES<\/b><\/h3>\r\nEthiopia:<\/b> Shungura Deposits\r\n\r\nKenya:<\/b> West Lake Turkana\r\n

PEOPLE<\/b><\/h3>\r\nYves Coppens, Camille Arambourg, and Alan Walker\r\n\r\n<\/div>\r\n

INTRODUCTION<\/strong><\/h2>\r\nAustralopithecus aethiopicus<\/i> is the most primitive of the robust species. I use genus Australopithecus<\/i> because it is thought to be descended from Au. afarensis<\/i>. In addition, Paranthropus<\/i> was the genus name assigned to the South African robust form, P. robustus<\/i>, and questions remain as to whether the two species are related.\r\n

PHYLOGENY<\/b><\/h2>\r\nThere are multiple lines of evidence to support Au. aethiopicus<\/i> as a descendent species of Au. afarensis<\/i>. While some believe that Au. aethiopicus <\/i>gave rise to P. boisei<\/i>, others link P. boisei<\/i> with P. robustus<\/i> in a different clade, with Au. africanus<\/i> as their common ancestor. More recently discovered material within the geographic range of Au. aethiopicus<\/i> supports the Au. aethiopicus<\/i> \u2192 P. boisei<\/i> evolutionary scenario. The dates of the new fossils fall between the two species, and they possess intermediate or transitional characteristics. Figure 17.2\u00a0shows one cladistic schema that illustrates how some researchers suggest these species were related. This particular scenario shows the authors\u2019 belief that Au. africanus<\/i> is a robust form.\r\n\r\n[caption id=\"attachment_224\" align=\"aligncenter\" width=\"234\"]\"7.39\" Figure 17.2\u00a0<\/em>Cladistic analysis of early hominins. \u201cCladistic analysis of early hominins<\/a>\u201d by Charles T. G. Clarke is licensed under CC BY-SA 3.0<\/a>.[\/caption]\r\n

DISCOVERY AND GEOGRAPHIC RANGE<\/b><\/h2>\r\nIn 1967, the earliest Au. aethiopicus <\/i>fossils were discovered by Yves Coppens and Camille Arambourg in the Shungura deposits at the site of Omo in southern Ethiopia. They assigned them to a new genus and species, Paraustralopithecus aethiopicus<\/i>. While it was debatable as to whether they actually had a new species, the discovery of the \u201cBlack Skull\u201d (see Figure 17.1) in the West Lake Turkana region of Kenya by Alan Walker in 1985 put any doubts to rest. At that time, the species was added to genus Australopithecus<\/i> because it was thought to be descended from Au. afarensis<\/i>. There were then three recognized species of robust australopiths in Africa, and efforts to determine their phylogenetic relationships began.\r\n\r\nThe Black Skull or KNM-WT (Kenya National Museum \u2013 West Turkana) 15000 was a magnificent find. The almost complete skull was stained from manganese, but it is always fun to sing scary movie music to my students when introducing \u2026 THE BLACK SKULL! (Figure 17.3 ... for fun!)\r\n\r\n[caption id=\"attachment_225\" align=\"aligncenter\" width=\"300\"]\"7.40\" Figure 17.3\u00a0<\/em>Skull and crossbones. \u201cCrossbones (PSF)<\/a>\u201d by Pearson Scott Foresman is in the public domain.[\/caption]\r\n

PHYSICAL CHARACTERISTICS<\/b><\/h2>\r\nA unique characteristic that ties Au. aethiopicus<\/i> to P. boisei<\/i> is a heart-shaped foramen magnum, as opposed to the more ovoid form seen in Au. africanus<\/i> and P. robustus<\/i>. Primitive characteristics shared with Au. afarensis<\/i> are the flat cranial base, small brain (~410 cc), long molars (mesiodistally, i.e. front to back versus side to side), and the degree of prognathism in the lower face. Because their faces were so broad and their brains so small, they exhibit a high degree of postorbital constriction (also known as waisting), i.e. the area between the face and braincase is narrow. Derived robust characteristics are buttressing of the skull, face, and mandible. Their muscles of mastication were incredibly strong, as evidenced by the sagittal crest running down the midline of their skull where the temporalis muscle originated. The sagittal crest was higher and more posteriorly placed than in the two more derived robust species. The zygomatics were large and flared to allow for passage of the temporalis muscle from the sagittal crest to insert on the mandible and to expand the attachment site for the masseter muscle, the other large muscle of mastication (see Figure 17.4). The zygomatics were more forwardly flared than in the other two robust species. They also had heavy nuchal (posterior neck) muscles to support the weight of their heavy face and skull, and the attachment sites\u00a0of those muscles on the posterior skull was also an expanded crest that converged with the sagittal crest, i.e. a compound sagittal-nuchal crest. Large brow ridges in the robust species offset the stress generated by biting down on hard foods. However, Au. aethiopicus<\/i>\u2019s brows were smaller than the other two species. Their third maxillary molars were convergent, meaning they were positioned more medially than the first and second. While some researchers disagree, others find evidence for a more derived venous sinus system in the crania of the robust forms. The system consists of large collecting veins that ultimately empty into the jugular veins, allowing for rapid, gravity-fed blood drain from the brain, in order to keep fresh blood pumping in via several arterial systems. The largest and most superficial of those sinuses (see Figure 17.5) leave impressions on the inside of the skull vault. Dean Falk\u2019s \u201cRadiator Theory\u201d argues that our ancestors needed to keep their brains cool as they increased in size in a hot, open environment. The system became more complex after the time of the australopiths.\r\n
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Review of Primitive Characteristics<\/h3>\r\n