Paranthropus aethiopicus

{{good article}} {{short description|Extinct species of hominin of East Africa}} {{Speciesbox | fossil_range = Pliocene-Pleistocene, {{fossilrange|2.7|2.3}} | image = Paranthropus aethiopicus.JPG | image_caption = Reconstruction of KNM WT 17000 | genus = Paranthropus | species = aethiopicus | authority = Arambourg and Coppens, 1968 | synonyms = *''Paraustralopithecus aethiopicus''<br/><small>Arambourg and Coppens, 1968</small> *''Australopithecus aethiopicus''<br/><small>Walker and Leakey, 1985 (preoccupied)</small> *''Australopithecus walkeri''<br/><small>Ferguson, 1989</small> }}

'''''Paranthropus aethiopicus''''' is an extinct species of robust australopithecine from the Late Pliocene to Early Pleistocene of East Africa about 2.7–2.3 million years ago. However, it is much debated whether or not ''Paranthropus'' is an invalid grouping and is synonymous with ''Australopithecus'', so the species is also often classified as '''''Australopithecus aethiopicus'''''.{{Refn|or ''Australopithecus walkeri'' as the former combination is preoccupied by a junior synonym of ''Australopithecus afarensis''}} Whatever the case, it is considered to have been the ancestor of the much more robust ''P. boisei''. It is debated if ''P. aethiopicus'' should be subsumed under ''P. boisei'', and the terms ''P. boisei'' sensu lato ("in the broad sense") and ''P. boisei'' sensu stricto ("in the strict sense") can be used to respectively include and exclude ''P. aethiopicus'' from ''P. boisei''.

Like other ''Paranthropus'', ''P. aethiopicus'' had a tall face, thick palate, and especially enlarged cheek teeth. However, likely due to its archaicness, it also diverges from other ''Paranthropus'', with some aspects resembling the much earlier ''A. afarensis''. ''P. aethiopicus'' is known primarily by the skull KNM WT 17000 from West Turkana, Kenya, as well as some jawbones from Koobi Fora; the Shungura Formation, Ethiopia; and Laetoli, Tanzania. These locations featured bushland to open woodland landscapes with edaphic (water-logged) grasslands.

==Taxonomy== ===Research history=== thumb|left|Locations of ''P. aethiopicus'' discoveries In 1968, French palaeontologist Camille Arambourg and Breton anthropologist Yves Coppens described "''Paraustralopithecus aethiopicus''" based on a toothless mandible (Omo 18) from the Shungura Formation, Ethiopia. The name ''aethiopicus'' refers to Ethiopia.<ref>{{cite journal|last1=Arambourg|first1=C.|author-link=Camille Arambourg|first2=Y.|last2=Coppens|author-link2=Yves Coppens|year=1968|title=Sur la decouverte dans le Pleistocene inferieur de la valle de l'Omo (Ethiopie) d'une mandibule d'Australopithecien|language=fr|trans-title=On the discovery in the Lower Pleistocene Omo Valley (Ethiopia) of an Australopithecine Mandible|journal=Comptes Rendus des Séances de l'Académie des Sciences|volume=265|pages=589–590}}</ref> In 1976, American anthropologist Francis Clark Howell and Coppens reclassified it as ''A. africanus''.<ref name=Ferguson1989>{{cite journal|first=W. W.|last=Ferguson|author-link=Walter Ferguson (painter)|year=1989|title=A New Species of the Genus ''Australopithecus'' (Primates: Hominidae) from Plio/Pleistocene Deposits West of Lake Turkana in Kenya|journal=Primates|volume=30|issue=2|pages=223–232|doi=10.1007/BF02381307|s2cid=28642451}}</ref>

In 1985, the skull KNM WT 17000 dating to 2.5 million years ago was reported from Koobi Fora, Lake Turkana, Kenya, by anthropologists Alan Walker and Richard Leakey. A partial jawbone from a different individual, KNM-WT 16005, was also discovered. They clearly belonged to a robust australopithecine.<ref name=Walker1986/> By this point in time, much younger robust australopithecines had been reported from South Africa (''robustus'') and East Africa (''boisei''), and been variously assigned to either ''Australopithecus'' or a unique genus ''Paranthropus''.<ref name=wood2/> Walker and Leakey assigned KNM WT 17000 to the ''boisei'' clade. They noted several anatomical differences, but were unsure if this stemmed from the specimens' archaicness or represented the normal range of variation for the species. If the former, they recommended classifying them and similar specimens into a different species, ''aethiopicus'' (and recommended that ''Paraustralopithecus'' be invalid). The discovery of these archaic specimens overturned previous postulations that ''P. robustus'' was the ancestor of the much more robust ''P. boisei'' (a hypothesis notably argued by palaeoanthropologist Yoel Rak in 1985) by establishing the ''boisei'' lineage as beginning long before ''robustus'' had existed.<ref name=Walker1986>{{cite journal|first1=A.|last1=Walker|author-link=Alan Walker (anthropologist)|first2=R. E.|last2=Leakey|author2-link=Richard Leakey|first3=J. M.|last3=Harris|first4=F. H.|last4=Brown|year=1986|title=2.5-Myr Australopithecus boisei from west of Lake Turkana, Kenya|journal=Nature|volume=322|issue=6079|pages=517–522|doi=10.1038/322517a0|bibcode=1986Natur.322..517W|s2cid=4270200}}</ref>

In 1989, palaeoartist Walter Ferguson recommended KNM WT 17000 be classified into a different species, ''walkeri'', because the holotype of ''aethiopicus'' comprised only the jawbone and KNM WT 17000 preserves no jaw elements.<ref name=Ferguson1989/> Ferguson's classification is almost universally ignored,<ref>{{cite book|url=https://books.google.com/books?id=440TmWXToLAC&pg=PT298|first=B.|last=Wood|title=Wiley-Blackwell Encyclopedia of Human Evolution|publisher=John Wiley & Sons|pages=298–299|isbn=978-1-4443-4247-5|year=2011}}</ref> and is considered to be synonymous with ''P. aethiopicus''.<ref>{{cite book|first1=R.|last1=Leakey|author-link=Richard Leakey|first2=R.|last2=Lewin|author-link2=Roger Lewin|year=1993|title=Origins Reconsidered: In Search of what Makes Us Human|url=https://books.google.com/books?id=KQULA9F9--IC&pg=PA362|publisher=Anchor Books|pages=132–133|isbn=978-0-385-46792-6}}</ref>

Several more lower and upper jaw specimens have been unearthed in the Shungura Formation,<ref name=wood2/>{{rp|112–113}} including a juvenile specimen, L338y-6.<ref name=Wood1994/> In 2002, a 2.7–2.5 Ma maxilla, EP 1500, from Laetoli, Tanzania, was assigned to ''P. aethiopicus''. Also found was the upper portion of a tibia, but it cannot definitively be associated with EP 1500 and thus with ''P. aethiopicus''.<ref>{{cite journal|first=T.|last=Harrison|year=2002|title=The first record of fossil hominins from the Ndolanya Beds, Laetoli, Tanzania|journal=American Journal of Physical Anthropology|volume=32|page=83}}</ref>

===Classification=== The genus ''Paranthropus'' (from Ancient Greek παρα ''para'' beside or alongside, and άνθρωπος ''ánthropos'' man,<ref>{{cite web|url=https://www.merriam-webster.com/dictionary/Paranthropus|title=''Paranthropus''|publisher=Merriam–Webster Dictionary|access-date=20 June 2020}}</ref> otherwise known as "robust australopithecines") typically includes ''P. aethiopicus'', ''P. boisei'', and ''P. robustus''. ''P. aethiopicus'' is the earliest member of the genus, with the oldest remains, from the Ethiopian Omo Kibish Formation, dated to 2.6 million years ago (mya) at the end of the Pliocene.<ref name=Constantino2007>{{cite journal|first1=P. J.|last1=Constantino|first2=B. A.|last2=Wood|year=2007|title=The Evolution of ''Zinjanthropus boisei''|journal=Evolutionary Anthropology|volume=16|issue=2|pages=49–62|doi=10.1002/evan.20130|s2cid=53574805|url=https://mds.marshall.edu/cgi/viewcontent.cgi?article=1027&context=bio_sciences_faculty|url-access=subscription}}</ref> It is possible that ''P. aethiopicus'' evolved even earlier, up to 3.3 mya, on the expansive Kenyan floodplains of the time.<ref name=Joordens2019>{{cite journal|first1=J. C. A.|last1=Joordens|first2=C. S.|last2=Feibel|first3=H. B.|last3=Vonhof|first4=A. S.|last4=Schulp|first5=D.|last5=Kroon|year=2019|title=Relevance of the eastern African coastal forest for early hominin biogeography|journal=Journal of Human Evolution|volume=131|pages=176–202|pmid=31182201|doi=10.1016/j.jhevol.2019.03.012|doi-access=free|bibcode=2019JHumE.131..176J |hdl=20.500.11820/6c1ee960-79ba-45df-9e12-3350c768a497|hdl-access=free}}</ref> ''P. aethiopicus'' is only confidently identified from the skull KNM WT 17000 and a few jaws and isolated teeth, and is generally considered to have been ancestral to ''P. boisei'' which also inhabited East Africa, making it a chronospecies. Because of this relationship, it is debatable if ''P. aethiopicus'' should be subsumed under ''P. boisei'' or if the differences stemming from archaicness should justify species distinction. The terms ''P. boisei sensu lato'' ("in the broad sense") and ''P. boisei sensu stricto'' ("in the strict sense") can be used to respectively include and exclude ''P. aethiopicus'' from ''P. boisei'' when discussing the lineage as a whole.<ref name=wood2/>{{rp|106–107}}

It is also debated if ''Paranthropus'' is a valid natural grouping (monophyletic) or an invalid grouping of similar-looking hominins (paraphyletic). Because skeletal elements are so limited in these species, their affinities with each other and to other australopithecines is difficult to gauge with accuracy. The jaws are the main argument for monophyly, but such anatomy is strongly influenced by diet and environment, and could in all likelihood have evolved independently in ''P. boisei'' and ''P. robustus''. Proponents of monophyly consider ''P. aethiopicus'' to be ancestral to the other two species, or closely related to the ancestor. Proponents of paraphyly allocate these three species to the genus ''Australopithecus'' as ''A. boisei'', ''A. aethiopicus'', and ''A. robustus''. British geologist Bernard Wood and American palaeoanthropologist William Kimbel are major proponents of monophyly, and against include Walker.<ref name=wood2>{{cite journal |first1=Bernard |last1=Wood |first2=Paul |last2=Constantino |year=2007 |title=''Paranthropus boisei'': Fifty years of evidence and analysis |journal=American Journal of Physical Anthropology |volume=134|issue=Suppl 45 |pages=106–32 |pmid=18046746 |doi=10.1002/ajpa.20732|url=https://mds.marshall.edu/cgi/viewcontent.cgi?article=1035&context=bio_sciences_faculty |doi-access=free }}</ref>{{rp|117–121}}

{{clade gallery |align=centre |height=225px|main-borders= |main-footer=Three example family trees with ''P. robustus'' (note, they are not absolute) |caption1=Monophyly<ref name=wood2/>{{rp|119}} |caption2=Paraphyly<ref name=wood2/>{{rp|119}} |caption3=Monophyly<ref name=McNulty2016>{{cite journal|first=K. P.|last=McNulty|year=2016|title=Hominin Taxonomy and Phylogeny: What's In A Name?|journal=Nature Education Knowledge|volume=7|issue=1|page=2|url=https://www.nature.com/scitable/knowledge/library/hominin-taxonomy-and-phylogeny-what-s-in-142102877/}}</ref> |cladogram1= {{clade |1={{clade |1=''A. africanus'' |2={{clade |1='''''P. aethiopicus''''' |2={{clade |1=''P. boisei'' |2=''P. robustus'' }} }} }} }} |cladogram2= {{clade |1={{clade |1={{clade |1=''A. africanus'' |2=''P. robustus'' }} |2={{clade |1='''''P. aethiopicus''''' |2=''P. boisei'' }} }} }} |cladogram3= {{clade |1={{clade |label1=''A. africanus'' |1={{clade |1=''Homo'' |2=''Australopithecus sediba'' }} |2={{clade |1=''A. garhi'' |label2='''''P. aethiopicus''''' |2={{clade |1=''P. boisei'' |2=''P. robustus'' }} }} }}}} }}This species, originally named ''Paraustralopithecus aethiopicus'', cannot retain the species epithet ''aethiopicus'' if moved to genus ''Australopithecus'' because ''Australopithecus aethiopicus'' is already a junior synonym of ''Australopithecus afarensis''. Such a classification would have to use the name '''''Australopithecus walkeri''''' for this species. The change of species epithet would also happen in a taxonomy that classifies all hominins as ''Homo''.<ref>{{Cite journal|last=Groves|first=Colin P.|date=1999-12-01|title=Nomenclature of African Plio-Pleistocene hominins|url=http://www.sciencedirect.com/science/article/pii/S0047248499903664|journal=Journal of Human Evolution|language=en|volume=37|issue=6|pages=869–872|doi=10.1006/jhev.1999.0366|pmid=10600324|bibcode=1999JHumE..37..869G |issn=0047-2484|url-access=subscription}}</ref>

==Description== {{Multiple image|align=left|total_width=350px|image1=Paranthropus aethiopicus at the Natural History Museum cropped.jpg|image2=Paranthropus aethiopicus face (University of Zurich).JPG|footer=Reconstruction of KNM WT 17000, side view (left) and face (right)}} Typical of ''Paranthropus'', KNM WT 17000 is heavily built, and the palate and base of the skull are about the same size as the ''P. boisei'' holotype OH 5. The brain volume of KNM WT 17000 was estimated to have been {{cvt|410|cc}}, which is smaller than that of other ''Paranthropus''. The combination of a tall face, thick palate, and small braincase caused a highly defined sagittal crest on the midline of the skull. The only complete tooth crown of the specimen is the right third premolar, whose dimensions are well above the range of variation for ''P. robustus'' and on the upper end for ''P. boisei''. Unlike other ''Paranthropus'', KNM WT 17000 did not have a flat face, and the jaw jutted out (prognathism). In regard to the temporal bone, KNM WT 17000 differs from other ''Paranthropus'' in that the squamous part of temporal bone is extensively pneumaticised, the tympanic part of the temporal bone is not as vertically orientated, the base of the skull is weakly flexed, the postglenoid process is completely anterior to (in front of) the tympanic, the tympanic is somewhat tubular, and the articular tubercle is weak. Like ''P. boisei'', the foramen magnum where the skull connects to the spine is heart-shaped.<ref name=Walker1986/> The temporalis muscle was probably not directed as forward as it was in ''P. boisei'', meaning the ''P. aethiopicus'' jaw likely processed food with the incisors before using the cheek teeth. The incisors of ''P. boisei'' are thought to have not been involved in processing food. The long distance between the first molar and the jaw hinge would suggest KNM WT 17000 had an exceptionally long ramus of the mandible (connecting the lower jaw to the skull), though the hinge's location indicates the ramus would not have been particularly deep (it would have been weaker). This may have produced a less effective bite compared to ''P. boisei''.<ref name=Wood1994>{{cite journal|first1=B.|last1=Wood|first2=C.|last2=Wood|first3=L.|last3=Konigsberg|year=1994|title=''Paranthropus boisei'': an example of evolutionary stasis?|journal=American Journal of Physical Anthropology|volume=95|issue=2|pages=132–134|doi=10.1002/ajpa.1330950202|pmid=7802091}}</ref>

[[File:Australopithecus boisei Peninj 1 IMG 5626 BMNH.jpg|thumb|Cast of the Peninj Mandible assigned to ''P. boisei'', which is similar to KNM-WT 16005]] KNM-WT 16005 is quite similar to the Peninj Mandible assigned to ''P. boisei'', exhibiting postcanine megadontia with relatively small incisors and canines (based on the tooth roots) and large cheek teeth.<ref name=Walker1986/> Nonetheless, the incisors were likely much broader in KNM-WT 16005.<ref name=Wood1994/> KNM-WT 16005 preserved four cheek teeth on the left side: the third premolar measuring {{cvt|10.7x13.8|mm}}, the fourth premolar measuring {{cvt|12x15|mm}}, the first molar measuring {{cvt|15.7x14.3|mm}}, and the second molar measuring {{cvt|17x16.7|mm}}. The fourth premolar and first molar are a little smaller than those of the Peninj mandible, and the second molar a bit bigger. The KNM-WT 16005 jawbone is smaller than what KNM WT 17000 would have had.<ref name=Walker1986/>

Many of these ''P. aethiopicus'' features are shared with the early ''A. afarensis'', further reiterating the species' archaicness.<ref name=Walker1986/><ref name=Wood1994/>

==Palaeoecology== In general, ''Paranthropus'' are thought to have been generalist feeders, with the heavily built skull becoming important when chewing less desirable, lower quality foods in times of famine. Unlike ''P. boisei'' which generally is found in the context of closed, wet environments, ''P. aethiopicus'' seems to have inhabited bushland to open woodland habitats around edaphic (water-logged) grasslands.<ref name=wood2/>{{rp|121}} Around 2.5 million years ago, at the Pliocene/Pleistocene border, the Omo–Turkana Basin featured a mix of forests, woodlands, grasslands, and bushlands, though grasslands appear to have been expanding through the Early Pleistocene. ''Homo'' seems to have entered the region 2.5–2.4 million years ago.<ref>{{cite book|first1=R.|last1=Bobe|first2=M.|last2=Leakey|author2-link=Meave Leakey|chapter=Ecology of Plio-Pleistocene Mammals in the Omo–Turkana Basin and the Emergence of ''Homo''|year=2009|title=The First Humans - Origin and Early Evolution of the Genus ''Homo''|publisher=Springer Science+Business Media|pages=181–182|isbn=978-1-4020-9980-9|doi=10.1007/978-1-4020-9980-9}}</ref>

==See also== {{div col|colwidth=30em}} * {{annotated link|African archaeology}} * {{annotated link|Australopithecus garhi|''Australopithecus garhi''}} * {{annotated link|Australopithecus afarensis|''Australopithecus afarensis''}} * {{annotated link|Australopithecus africanus|''Australopithecus africanus''}} * {{annotated link|Homo habilis|''Homo habilis''}} * {{annotated link|Homo rudolfensis|''Homo rudolfensis''}} * {{annotated link|LD 350-1}} * {{annotated link|Paranthropus boisei|''Paranthropus boisei''}} * {{annotated link|Paranthropus robustus|''Paranthropus robustus''}} {{div col end}}

==References== {{Reflist}}

== External links == * {{commons-inline|2=''Paranthropus aethiopicus''}} * [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – Smithsonian, National Museum of Natural History (August 2016). {{Human Evolution}} {{Portal bar|Evolutionary biology|Paleontology}} {{Taxonbar|from=Q310517}}

Category:Paranthropus Category:Pliocene primates Category:Fossil taxa described in 1968 Category:Prehistoric Kenya Category:Pleistocene mammals of Africa Category:Pleistocene primates