View source for Australopithecus bahrelghazali

{{good article}}
{{Short description|Extinct species of hominin from 3.5 mya}}
{{Speciesbox
| fossil_range = [[Piacenzian]] {{fossil range|3.6/3.5|3}}
| image = Australopithecos bahrelghazali.jpg
| image_caption = Australopithecus bahrelghazali appearance
| extinct = yes
| genus = Australopithecus
| species = bahrelghazali
| authority = [[Michel Brunet (paleontologist)|Brunet]] et al., 1995
| synonyms = ''Praeanthropus bahrelghazali''
}}

'''''Australopithecus bahrelghazali''''' is an [[extinct]] [[species]] of [[australopithecine]] discovered in 1995 at [[Koro Toro]], [[Bahr el Gazel (region of Chad)|Bahr el Gazel]], Chad, existing around 3.5 million years ago in the [[Pliocene]]. It is the first and only australopithecine known from [[Central Africa]], and demonstrates that this group was widely distributed across Africa as opposed to being restricted to East and southern Africa as previously thought. The validity of ''A. bahrelghazali'' has not been widely accepted, in favour of classifying the specimens as ''[[Australopithecus afarensis|A. afarensis]]'', a better known Pliocene australopithecine from East Africa, because of the anatomical similarity and the fact that ''A.  bahrelghazali'' is known only from 3 partial jawbones and an isolated [[premolar]]. The specimens inhabited a lakeside grassland environment with sparse tree cover, possibly similar to the modern [[Okavango Delta]], and similarly predominantly ate [[C4 carbon fixation|C<sub>4</sub>]] savanna foods—such as grasses, sedges, [[storage organ]]s, or [[rhizome]]s—and to a lesser degree also [[C3 carbon fixation|C<sub>3</sub>]] forest foods—such as fruits, flowers, pods, or insects. However, the teeth seem ill-equipped to process C<sub>4</sub> plants, so its true diet is unclear.

==Research history==
{{Multiple image|align=left|image1=Africa, australopitecines discovery sites.png|image2=Koro-Toro.jpg|width2=130|footer=Australopithecus locations (left) and within Chad with [[Lake Chad|Lake Mega-Chad]] outlined (right)}}
In 1995, two specimens were recovered from [[Koro Toro]], [[Bahr el Gazel (region of Chad)|Bahr el Gazel]], Chad: KT12/H1 or "[[Abel (hominid)|Abel]]" (a jawbone preserving the premolars, [[canine (tooth)|canines]], and the right second [[incisor]]) and KT12/H2 (an isolated first upper [[premolar]]). They were discovered by the Franco-Chadian Paleoanthropological Mission, and reported by French palaeontologist [[Michel Brunet (paleontologist)|Michel Brunet]], French geographer Alain Beauvilain, French anthropologist [[Yves Coppens]], French palaeontologist Emile Heintz, Chadian geochemist engineer Aladji Hamit Elimi Ali Moutaye, and British palaeoanthropologist [[David Pilbeam]]. Based on the wildlife assemblage, the remains were roughly dated to the middle to late [[Pliocene]] 3.5–3 million years ago; consequently, the describers decided to preliminarily assign the remains to ''[[Australopithecus afarensis]]'', which inhabited Ethiopia during that time period, barring more detailed anatomical comparisons.<ref name=Brunet1995>{{cite journal | last1 = Brunet | first1 = M.|author-link=Michel Brunet (paleontologist) | last2 = Beauvilain |first2 = A. | author3-link = Yves Coppens | author6-link = David Pilbeam | last3 = Coppens | first3 = Y. | last4 = Heintz | first4 = É. | last5 = Moutaye | first5 = A. H. E | last6 = Pilbeam | first6 = D. | s2cid = 4365908| year = 1995 | title = The first australopithecine 2,500 kilometres west of the Rift Valley (Chad)| journal = Nature | volume = 378 | issue = 6554| pages = 273–275 | doi=10.1038/378273a0| pmid = 7477344 | bibcode = 1995Natur.378..273B }}</ref> In 1996, they allocated it to a new species, ''A. bahrelghazali'', naming it after the region; Bahr el Gazel means "River of the Gazelles" in [[classical Arabic]]. They denoted KT12/H1 as the [[holotype]] and KT12/H2 a [[paratype]].<ref>{{cite journal |first1=Michel |last1=Brunel |author-link=Michel Brunet (paleontologist) |last2=Beauvilain |first2=A. |last3=Coppens |first3=Yves |author-link3=Yves Coppens |last4=Heintz |first4=É. |last5=Moutaye |first5=A. H. E |last6=Pilbeam |first6=D. |year=1996 |url=https://afanporsaber.com/wp-content/uploads/2017/09/Australopithecus-bahrelghazali-une-nouvelle-esp%C3%A8ce-dHominid%C3%A9-ancien-de-la-r%C3%A9gion-de-Koro-Toro-Tchad.pdf |title=''Australopithecus bahrelghazali'', une nouvelle espèce d'Hominidé ancien de la région de Koro Toro (Tchad)|trans-title=''Australopithecus bahrelghazali'', a new species of fossil hominid from Koro Toro (Chad) |journal=Comptes Rendus des Séances de l'Académie des Sciences |volume=322 |pages=907–913}}</ref> Another jawbone was discovered at the K13 site in 1997,<ref>{{cite journal|first1=M.|last1=Brunet|author-link=Michel Brunet (paleontologist)|first2=A.|last2=Beauvilain|display-authors=et al.|year=1997|title=Tchad : un nouveau site à Hominidés Pliocène|journal=Comptes rendus des séances de l'Académie des Sciences|volume=324|pages=341–345}}</ref> and a third from the KT40 site.<ref name=Guy2008>{{cite journal|first1=F.|last1=Guy|first2=H.-T.|last2=Mackaye|display-authors=et al.|year=2008|title=Symphyseal shape variation in extant and fossil hominoids, and the symphysis of ''Australopithecus bahrelghazali''|journal=Journal of Human Evolution|volume=55|issue=1|pages=37–47|doi=10.1016/j.jhevol.2007.12.003|pmid=18222528}}</ref>

In 2008, a [[pelite]] (a type of [[sedimentary rock]]) recovered from the same sediments as Abel was [[radiometric dating|radiometrically dated]] (using the [[beryllium-10|<sup>10</sup>Be]]/[[beryllium-9|<sup>9</sup>Be]] ratio) to have been deposited 3.58 million years ago.<ref>{{cite journal | last1 = Lebatard | first1 = A.-E. | author-link14 = Michel Brunet (paleontologist) | last2 = Bourlès | first2 = D. L. | last3 = Duringer | first3 = P. | last4 = Jolivet | first4 = M. | last5 = Braucher | first5 = R.| last6 = Carcaillet | first6 = J. | last7 = Schuster | first7 = M. | last8 = Arnaud | first8 = N. | last9 = Monié | first9 = P. | last10 = Lihoreau | first10 = F.| last11 = Likius | first11 = A. | last12 = Taisso Mackaye | first12 = H. | last13 = Vignaud | first13 = P. | last14 = Brunet | first14 = M. | year = 2008 | title = Cosmogenic nuclide dating of ''Sahelanthropus tchadensis'' and ''Australopithecus bahrelghazali'': Mio-Pliocene hominids from Chad | journal = Proceedings of the National Academy of Sciences| volume = 105 | issue = 9| pages = 3226–3231 | doi=10.1073/pnas.0708015105| pmid = 18305174 | pmc = 2265126 | bibcode = 2008PNAS..105.3226L | doi-access = free }}</ref> However, Beauvilain responded that Abel was not found ''[[in situ]]'' but at the edge of a shallow gulley, and it is impossible to figure out from what [[stratigraphic section]] the specimen (or any other fossil from Koro Toro) was first deposited in, in order to accurately radiometrically date it.<ref>{{cite journal|first=A.|last=Beauvilain|year=2008|title=The contexts of discovery of ''Australopithecus bahrelghazali'' (Abel) and of ''Sahelanthropus tchadensis'' (Toumaï): unearthed, embedded in sandstone, or surface collected?|journal=South African Journal of Science|volume=104|issue=5–6|pages=165–168|url=https://journals.co.za/docserver/fulltext/sajsci/104/5/sajsci_v104_n5_6_a3.pdf?expires=1593546874&id=id&accname=guest&checksum=CF63D5EB475A1DBAD87C5F089D75593C}}</ref> Nonetheless, Abel was redated in 2010 using the same methods to about 3.65 million years ago,<ref>{{cite journal|first1=A.-E.|last1=Lebetard|first2=D. L.|last2=Bourlès|first3=R.|last3=Braucher|display-authors=et al.|year=2010|title=Application of the authigenic <sup>10</sup>Be/<sup>9</sup>Be dating method to continental sediments: Reconstruction of the Mio-Pleistocene sedimentary sequence in the early hominid fossiliferous areas of the northern Chad Basin|journal=Earth and Planetary Science Letters|volume=297|issue=1–2|pages=57–70|doi=10.1016/j.epsl.2010.06.003|bibcode=2010E&PSL.297...57L}}</ref> and Brunet agreed with an age of roughly 3.5 million years ago.<ref name=Brunet2010/>

''A. bahrelghazali'' was the first [[australopithecine]] recovered from Central Africa, and disproved the earlier notion that they were restricted to east of the eastern branch of the [[East African Rift]] which formed in the [[Late Miocene]]. Koro Toro is situated about {{cvt|2500|km}} from the Rift Valley, and the remains suggest australopithecines were widely distributed in grassland and woodland zones across the continent. The lack of other Central and West African australopithecines may be due to [[sampling bias]], as similarly aged fossil-bearing sediments are more or less unknown beyond East Africa.<ref name=Brunet1995/> The ancestors of ''A. bahrelghazali'' may have left East Africa via the [[Central African Shear Zone]].<ref name=Macho2015/> In 2014, the first australopithecine in the western branch of the East African Rift was reported in [[Ishango]], Democratic Republic of the Congo.<ref>{{cite journal|first1=I.|last1=Crevecoeur|first2=M. M.|last2=Skinner|first3=S. E.|last3=Bailey|display-authors=et al.|year=2014|title=First Early Hominin from Central Africa (Ishango, Democratic Republic of Congo)|journal=PLOS ONE|volume=9|issue=1|page=e84652|doi=10.1371/journal.pone.0084652|pmc=3888414|pmid=24427292|bibcode=2014PLoSO...984652C|doi-access=free}}</ref> 

At present, the classification of ''Australopithecus'' and ''Paranthropus'' species is in disarray. ''Australopithecus'' is considered a [[evolutionary grade|grade taxon]] whose members are united by their similar physiology rather than how close they are to each other in the hominin family tree. In an attempt to resolve this, in 2003, Spanish writer [[Camilo José Cela Conde]] and evolutionary biologist [[Francisco J. Ayala]] proposed splitting off the genus "''Praeanthropus''" and including ''A. bahrelghazali'' alongside ''[[Sahelanthropus]]'' (the only other fossil ape known from Chad), ''[[Australopithecus anamensis|A. anamensis]]'', ''A. afarensis'', and ''[[Australopithecus garhi|A. garhi]]''.<ref name="Cela-CondeAyala2003">{{Cite journal | last1 = Cela-Conde | first1 = C. J.|author1-link=Camilo José Cela Conde| last2 = Ayala | first2 = F. J. |author2-link=Francisco J. Ayala| title = Genera of the human lineage | doi = 10.1073/pnas.0832372100 | journal = Proceedings of the National Academy of Sciences | volume = 100 | issue = 13 | pages = 7684–7689 | year = 2003 | pmid = 12794185| pmc = 164648 | bibcode = 2003PNAS..100.7684C| doi-access = free}}</ref>

The validity of ''A. bahrelghazali'' has not been widely accepted given how few remains there are and how similar they are to ''A. afarensis''.<ref>{{cite journal|first1=F.|last1=Spoor|first2=M. G.|last2=Leakey|author2-link=Meave Leakey|first3=P.|last3=O'Higgins|year=2016|title=Middle Pliocene hominin diversity: ''Australopithecus deyiremeda'' and ''Kenyanthropus platyops''|journal=Philosophical Transactions of the Royal Society B|volume=371|issue=1698|page=20150231|doi=10.1098/rstb.2015.0231|pmc=4920288|pmid=27298462}}</ref>
{{African hominin timeline}}

==Anatomy==
{{Human timeline}}
The teeth of KT12/H1 are quite similar to the jawbone of ''A. afarensis'', with large and incisor-like canines and bicuspid premolars (as opposed to [[molar (tooth)|molar]]-like premolars). Unlike ''A. afarensis'', the [[alveolar part of mandible|alveolar part of the jawbone]] where the [[tooth socket]]s are is almost vertical as opposed to oblique, possesses poorly developed superior transverse torus and moderate inferior torus (two ridges on the midline of the jaw on the tongue side), and thin [[tooth enamel|enamel]] on the chewing surface of the premolars.<ref name=Brunet1995/> Brunet and colleagues had listed the presence of 3 distinct tooth roots as a distinguishing characteristic, but the third premolar of the  ''A. afarensis'' LH-24 specimen from [[Middle Awash]], Ethiopia, was described in 2000 as having the same feature, which shows that premolar anatomy was highly variable for ''A. afarensis''.<ref>{{cite journal|first1=T. D.|last1=White|first2=G.|last2=Suwa|author2-link=Gen Suwa|first3=S.|last3=Simpson|first4=B.|last4=Asfaw|author4-link=Berhane Asfaw|year=2000|title=Jaws and teeth of ''Australopithecus afarensis'' from Maka, Middle Awash, Ethiopia|journal=American Journal of Physical Anthropology|volume=111|issue=1|page=66|doi=10.1002/(SICI)1096-8644(200001)111:1<45::AID-AJPA4>3.0.CO;2-I|pmid=10618588 }}</ref> The [[mandibular symphysis]] (at the midline of the jaw) of KT40, especially, as well as KT12/H1 have the same dimensions as the symphysis of ''A. afarensis'', though theirs is relatively thick compared to the height.<ref name=Guy2008/>

==Palaeoecology==
[[Isotope analysis#Carbon-13|Carbon isotope analysis]] indicates a diet of predominantly [[C4 carbon fixation|C<sub>4</sub>]] savanna foods, such as grasses, sedges, underground [[storage organ]]s (USOs), or [[rhizome]]s. There is a smaller [[C3 carbon fixation|C<sub>3</sub>]] portion which may have comprised more typical ape food items such as fruits, flowers, pods, or insects. This indicates that, like contemporary and future australopiths, ''A. bahrelghazali'' was capable of exploiting whatever food was abundant in its environment, whereas most primates (including savanna chimps) avoid C<sub>4</sub> foods.<ref name=Lee2012>{{cite journal|first1=J.|last1=Lee-Thorp|author-link=Julia Lee-Thorp|first2=A.|last2=Likius|first3=H. T.|last3=Mackaye|s2cid=37279343|display-authors=et al.|year=2012|title=Isotopic evidence for an early shift to C4 resources by Pliocene hominins in Chad|journal=Proceedings of the National Academy of Sciences|volume=109|issue=50|pages=20369–20372|doi=10.1073/pnas.1204209109|pmid=23150583|pmc=3528505|doi-access=free}}</ref> However, despite 55–80% of δ<sup>13</sup>C deriving from C<sub>4</sub> sources similar to ''[[Paranthropus boisei]]'' and the modern [[gelada]] (and considerably more than any tested ''A. afarensis'' population), ''A. bahrelghazali'' lacks the specialisations for such a diet. Because the teeth are not [[hypsodont]], it could not have chewed large quantities of grass, and because the enamel is so thin, the teeth would not have been able to withstand the abrasive dirt particles of USOs. In regard to C<sub>4</sub> sources, chimps and [[bonobo]]s (which have even thinner enamel) consume plant [[pith|medullas]] as a fallback food and sedges as an important energy and protein source; however a sedge-based diet likely could not have sustained ''A. bahrelghazali''.<ref name=Macho2015>{{cite journal|first=G. A.|last=Macho|year=2015|title=Pliocene hominin biogeography and ecology|journal=Journal of Human Evolution|volume=87|pages=78–86|doi=10.1016/j.jhevol.2015.06.009|pmid=26198846}}</ref>

[[File:Okavango Delta, Botswana.jpg|thumb|left|[[Koro Toro]] may have been similar to the modern [[Okavango Delta]] (above)]]
During the Pliocene around the expanded [[Lake Chad]] (or "Lake Mega-Chad"), insect [[trace fossil]]s indicate this was a well-vegetated region, and the abundance of [[rhizome]]s may suggest a seasonal climate with wet and dry seasons.<ref>{{cite journal|first1=M.|last1=Schuster|first2=P.|last2=Duringer|first3=J.-F.|last3=Ghienne|display-authors=et al.|year=2009|title=Chad Basin: Paleoenvironments of the Sahara since the Late Miocene|journal=Comptes Rendus Geoscience|volume=341|issue=8–9|pages=603–611|doi=10.1016/j.crte.2009.04.001|bibcode=2009CRGeo.341..603S|s2cid=133162696 |url=https://comptes-rendus.academie-sciences.fr/geoscience/articles/10.1016/j.crte.2009.04.001/ |url-access=subscription}}</ref> Koro Toro has yielded several large mammals, including several [[antelope]]s, of which some were [[endemism|endemic]], the [[elephant]] ''[[Loxodonta exoptata]]'', the [[white rhinoceros]] ''[[Ceratotherium praecox]]'', the [[Suidae|pig]] ''[[Kolpochoerus|Kolpochoerus afarensis]]'', a ''[[Hipparion]]'' [[horse]], a ''[[Sivatherium]]'', and a [[giraffe]]. Some of these are also known from Pliocene East African sites, implying that animals could freely migrate between east and west of the Great African Rift.<ref name=Brunet1995/> The K13 site features, in regard to [[bovid]]s, an abundance of [[Reduncinae]], [[Alcelaphinae]], and [[Antilopinae]], whereas [[Tragelaphini]] is much rarer, which indicates an open environment which was drier than Pliocene East African sites.<ref>{{cite journal|first1=D.|last1=Geraads|first2=M.|last2=Brunet|author2-link=Michel Brunet (paleontologist)|first3=H. T.|last3=Mackaye|first4=P.|last4=Vignaud|year=2000|title=Pliocene Bovidae (Mammalia) from the Koro Toro Australopithecine sites, Chad|journal=Journal of Vertebrate Paleontology|volume=21|issue=2|pages=335–346|doi=10.1671/0272-4634(2001)021[0335:PBMFTK]2.0.CO;2|s2cid=55934117 |url=https://halshs.archives-ouvertes.fr/halshs-00068080/file/Geraads162.pdf}}</ref> In total, the area seems to have been predominantly grasslands with some tree cover.<ref name=Lee2012/> In addition, the area featured aquatic creatures, predominantly [[catfish]], and also 10 other kinds of fish, the [[hippo]] ''[[Hexaprotodon|Hexaprotodon protamphibius]]'', an [[otter]], a ''[[Geochelone]]'' [[tortoise]], a ''[[Trionyx]]'' [[softshell turtle]], a [[false gharial]], and an [[anatid]] [[waterbird]]. These aquatic animals indicate Koro Toro had open-water lakes or streams with swampy grassy margins, connected to the Nilo-Sudan waterways (including the [[Nile]], [[Chari River|Chari]], [[Niger River|Niger]], [[Senegal River|Senegal]], [[Volta River|Volta]], and [[Gambia River|Gambia]] Rivers).<ref>{{cite journal|first1=O.|last1=Otero|first2=A.|last2=Pinton|first3=H. T.|last3=Mackaye|first4=A.|last4=Likius|first5=P.|last5=Vignaud|first6=M.|last6=Brunet|author6-link=Michel Brunet (paleontologist)|year=2010|title=The early/late Pliocene ichthyofauna from Koro-Toro, Eastern Djurab, Chad|journal=Geobios|volume=43|issue=2|pages=241–255|doi=10.1016/j.geobios.2009.10.003|bibcode=2010Geobi..43..241O }}</ref> Koro Toro, during Mega-Chad events (which have been cyclical for the last 7 million years), may have been similar to the modern [[Okavango Delta]].<ref name=Brunet2010>{{cite journal|first=M.|last=Brunet|author-link=Michel Brunet (paleontologist)|year=2010|title=Two new Mio-Pliocene Chadian hominids enlighten Charles Darwin's 1871 prediction|journal=Philosophical Transactions of the Royal Society B|volume=365|issue=1556|pages=3315–3321|doi=10.1098/rstb.2010.0069|pmc=2981960|pmid=20855305}}</ref>

== See also ==
{{div col|colwidth=30em}}
* [[African archaeology]]
* ''[[Ardipithecus ramidus]]''
* ''[[Australopithecus anamensis]]''
* ''[[Australopithecus afarensis]]''
* ''[[Australopithecus deyiremeda]]''
* ''[[Kenyanthropus]]''
* [[List of fossil sites]] (with link directory)
* [[List of human evolution fossils]] (with images)
{{div col end}}

==References==
{{Reflist|colwidth=30em}}

==External links==
{{Commons category}}
* [http://chadcradlehumanity.monsite-orange.fr/page-55da14b782d6d.html ''Australopithecus bahrelghazali'', Abel]
* [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – [[Smithsonian Institution|Smithsonian]], [[National Museum of Natural History]] (August 2016).
{{Human Evolution}}
{{Portal bar |Evolutionary biology|Paleontology | Africa}}
{{Taxonbar|from=Q310945}}

[[Category:Australopithecus]]
[[Category:Fossil taxa described in 1995]]
[[Category:Prehistoric Chad]]
[[Category:Pliocene primates]]
[[Category:Pliocene mammals of Africa]]