View source for Ardipithecus

{{Short description|Extinct genus of hominins}}
{{For|the album|Ardipithecus (album)}}
{{Automatic taxobox
 | fossil_range = [[Late Miocene]] - [[Early Pliocene]], {{fossil range|5.77|4.4}}
 | image = Ardi.jpg
 | image_caption = ''Ardipithecus ramidus'' specimen, nicknamed [[Ardi]]
 | taxon = Ardipithecus
 | authority = [[Tim D. White|White]] ''et al.'', 1995
 | subdivision_ranks = Species
 | subdivision = 
* †''[[Ardipithecus kadabba]]''
* †''[[Ardipithecus ramidus]]''
}}

'''''Ardipithecus''''' is a genus of an extinct [[hominine]] that lived during the [[Late Miocene]] and [[Early Pliocene]] epochs in the [[Afar Depression]], [[Ethiopia]]. Originally described as one of the earliest ancestors of humans after they diverged from the chimpanzees, the relation of this [[genus]] to human ancestors and whether it is a [[hominin]] is now a matter of debate.<ref name=cbs>{{cite journal |doi=10.1146/annurev-anthro-092611-145724 |ssrn=2158257 |title=Chimpanzees and the Behavior of Ardipithecus ramidus |journal=Annual Review of Anthropology |volume=41 |pages=139–49 |year=2012 |last1=Stanford |first1=Craig B. }}</ref> Two fossil [[species]] are described in the literature: ''[[A.&nbsp;ramidus]]'', which lived about 4.4 million years ago<ref name="NatGeo-News">{{cite web |url= http://news.nationalgeographic.com/news/2001/07/0712_ethiopianbones.html |archive-url= https://web.archive.org/web/20010715123225/http://news.nationalgeographic.com/news/2001/07/0712_ethiopianbones.html |url-status= dead |archive-date= July 15, 2001 |title=Fossils From Ethiopia May Be Earliest Human Ancestor |first=David |last=Perlman |publisher=National Geographic News |date=July 12, 2001 |access-date=March 18, 2017 |quote=Another co-author is Tim D. White, a paleoanthropologist at UC-Berkeley who in 1994 discovered a pre-human fossil, named Ardipithecus ramidus, that was then the oldest known, at 4.4 million years.}}</ref> during the early [[Pliocene]], and ''[[A.&nbsp;kadabba]]'', dated to approximately 5.6 million years ago (late [[Miocene]]).<ref name="AndThePaleobiology" /> Initial behavioral analysis indicated that ''Ardipithecus'' could be very similar to chimpanzees,<ref name=cbs/> however more recent analysis based on canine size and lack of canine sexual dimorphism indicates that ''Ardipithecus'' was characterised by reduced aggression,<ref>{{Cite web|first=Clare |last=Wilson |date=29 November 2021|title=Canine teeth shrank in human ancestors at least 4.5 million years ago|url=https://www.newscientist.com/article/2299286-canine-teeth-shrank-in-human-ancestors-at-least-4-5-million-years-ago/|access-date=2021-12-01|website=New Scientist|language=en-US}}</ref> and that they more closely resemble [[bonobo]]s.<ref>{{Cite journal |last1=Suwa |first1=Gen |last2=Sasaki |first2=Tomohiko |last3=Semaw |first3=Sileshi |last4=Rogers |first4=Michael J. |last5=Simpson |first5=Scott W. |last6=Kunimatsu |first6=Yutaka |last7=Nakatsukasa |first7=Masato |last8=Kono |first8=Reiko T. |last9=Zhang |first9=Yingqi |last10=Beyene |first10=Yonas |last11=Asfaw |first11=Berhane |last12=White |first12=Tim D. |date=2021-12-07 |title=Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like |journal=Proceedings of the National Academy of Sciences |language=en |volume=118 |issue=49 |doi=10.1073/pnas.2116630118 |doi-access=free |issn=0027-8424 |pmc=8670482 |pmid=34853174|bibcode=2021PNAS..11816630S }}</ref>

Some analyses describe ''Australopithecus'' as being sister to ''Ardipithecus ramidus'' specifically.<ref>{{cite thesis |last1=Pugh |first1=Kelsey |title=The Phylogenetic Relationships of Middle-Late Miocene Apes: Implications for Early Human Evolution |date=February 2020 |url=https://academicworks.cuny.edu/gc_etds/3619/ }}</ref> This means that ''[[Australopithecus]]'' is distinctly more closely related to ''Ardipithecus ramidus'' than ''Ardipithecus kadabba''. [[Cladistics|Cladistically]], then, ''Australopithecus'' (and eventually ''[[Homo sapiens]]'') indeed emerged within the ''Ardipithecus'' lineage, and this lineage is not literally extinct.

== ''Ardipithecus ramidus'' ==
{{Human timeline}}
{{Main|Ardipithecus ramidus}}
''A. ramidus'' was named in September 1994. The first fossil found was dated to 4.4 million years ago on the basis of its stratigraphic position between two volcanic [[stratum|strata]]: the basal [[Tuff|Gaala Tuff Complex]] (G.A.T.C.) and the [[basalt|Daam Aatu Basaltic Tuff]] (D.A.B.T.).<ref>{{cite journal |doi=10.1038/371306a0 |pmid=8090200 |title=Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopia |journal=Nature |volume=371 |issue=6495 |pages=306–12 |year=1994 |last1=White |first1=Tim D. |last2=Suwa |first2=Gen |last3=Asfaw |first3=Berhane |bibcode=1994Natur.371..306W |s2cid=4347140 }}</ref> The name ''Ardipithecus ramidus'' stems mostly from the [[Afar language]], in which ''Ardi'' means "ground/floor" and ''ramid'' means "root". The ''pithecus'' portion of the name is from the [[Greek language|Greek]] word for "ape".<ref name="NOVA">{{cite web |title=NOVA, Aliens from Earth: Who's who in human evolution |last=Tyson |first=Peter |date=October 2009 |publisher=PBS |access-date=2009-10-08 |url= https://www.pbs.org/wgbh/nova/hobbit/tree-nf.html}}</ref>

Like most [[hominid]]s, but unlike all previously recognized hominins, it had a grasping [[hallux]] or big toe adapted for locomotion in the trees. It is not confirmed how many other features of its skeleton reflect adaptation to [[bipedalism]] on the ground as well. Like later hominins, ''Ardipithecus'' had reduced [[Canine tooth|canine teeth]] and reduced canine sexual dimorphism.<ref>{{Cite web|last=#author.fullName}|title=Canine teeth shrank in human ancestors at least 4.5 million years ago|url=https://www.newscientist.com/article/2299286-canine-teeth-shrank-in-human-ancestors-at-least-4-5-million-years-ago/|access-date=2021-12-01|website=New Scientist|language=en-US}}</ref>

In 1992–1993 a research team headed by [[Tim D. White|Tim White]] discovered the first ''A. ramidus'' fossils—seventeen fragments including skull, mandible, teeth and arm bones—from the [[Afar Depression]] in the [[Middle Awash]] river valley of [[Ethiopia]]. More fragments were recovered in 1994, amounting to 45% of the total skeleton. This fossil was originally described as a species of ''[[Australopithecus]]'', but White and his colleagues later published a note in the same journal renaming the fossil under a new genus, ''Ardipithecus''. Between 1999 and 2003, a multidisciplinary team led by [[Sileshi Semaw]] discovered bones and teeth of nine ''A. ramidus'' individuals at [[As Duma]] in the [[Gona, Ethiopia|Gona area]] of Ethiopia's [[Afar Region]].<ref name="stoneageinstitute.org">{{cite web |title=New Fossil Hominids of Ardipithecus ramidus from Gona, Afar, Ethiopia |url= http://www.stoneageinstitute.org/news/gona_nature_paper.shtml#1 |access-date=2009-01-30 |archive-url= https://web.archive.org/web/20080624005441/http://www.stoneageinstitute.org/news/gona_nature_paper.shtml |archive-date=2008-06-24}}</ref> The fossils were dated to between 4.35 and 4.45 million years old.<ref>{{cite web|url= http://newsinfo.iu.edu/news/page/normal/1822.html |publisher=Indiana University |title=Anthropologists find 4.5 million-year-old hominid fossils in Ethiopia |access-date=March 18, 2017 }}</ref>
[[Image:Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg|thumb|left|300px|Map showing discovery locations.]]
''Ardipithecus ramidus'' had a small brain, measuring between 300 and 350&nbsp;cm<sup>3</sup>. This is slightly smaller than a modern bonobo or female chimpanzee brain, but much smaller than the brain of [[Australopithecus|australopithecines]] like Lucy (~400 to 550&nbsp;cm<sup>3</sup>) and roughly 20% the size of the modern ''Homo sapiens'' brain. Like common chimpanzees, ''A. ramidus'' was much more [[Prognathism|prognathic]] than modern humans.<ref name="Suwa_2009">{{cite journal |doi=10.1126/science.1175825 |pmid=19810194 |title=The Ardipithecus ramidus Skull and Its Implications for Hominid Origins |journal=Science |volume=326 |issue=5949 |pages=68e1–7 |year=2009 |last1=Suwa |first1=G. |last2=Asfaw |first2=B. |last3=Kono |first3=R. T. |last4=Kubo |first4=D. |last5=Lovejoy |first5=C. O. |last6=White |first6=T. D. |url= http://doc.rero.ch/record/211453/files/PAL_E4442.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://doc.rero.ch/record/211453/files/PAL_E4442.pdf |archive-date=2022-10-09 |url-status=live |bibcode=2009Sci...326...68S |s2cid=19725410 }}</ref>

The teeth of ''A. ramidus'' lacked the specialization of other apes, and suggest that it was a generalized [[omnivore]] and [[frugivore]] (fruit eater) with a diet that did not depend heavily on foliage, fibrous plant material (roots, tubers, etc.), or hard and or abrasive food. The size of the upper [[canine tooth]] in ''A. ramidus'' males was not distinctly different from that of females. Their upper canines were less sharp than those of modern common chimpanzees in part because of this decreased upper canine size, as larger upper canines can be honed through wear against teeth in the lower mouth. The features of the upper canine in ''A. ramidus'' contrast with the [[sexual dimorphism]] observed in common chimpanzees, where males have significantly larger and sharper upper canine teeth than females.<ref name="Suwa_2009b">{{cite journal |doi=10.1126/science.1175824 |pmid=19810195 |title=Paleobiological Implications of the Ardipithecus ramidus Dentition |journal=Science |volume=326 |issue=5949 |pages=94–9 |year=2009 |last1=Suwa |first1=G. |last2=Kono |first2=R. T. |last3=Simpson |first3=S. W. |last4=Asfaw |first4=B. |last5=Lovejoy |first5=C. O. |last6=White |first6=T. D. |bibcode=2009Sci...326...94S |s2cid=3744438 |url= http://doc.rero.ch/record/211460/files/PAL_E4443.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://doc.rero.ch/record/211460/files/PAL_E4443.pdf |archive-date=2022-10-09 |url-status=live }}</ref> Of the living apes, bonobos have the smallest canine sexual dimorphism, although still greater than that displayed by ''A. ramidus''.<ref>{{Cite web|last=#author.fullName}|title=Canine teeth shrank in human ancestors at least 4.5 million years ago|url=https://www.newscientist.com/article/2299286-canine-teeth-shrank-in-human-ancestors-at-least-4-5-million-years-ago/|access-date=2021-12-01|website=New Scientist|language=en-US}}</ref>

The less pronounced nature of the upper canine teeth in ''A. ramidus'' has been used to infer aspects of the [[Primatology#Primatology in sociobiology|social behavior]] of the species and more ancestral hominids. In particular, it has been used to suggest that the [[last common ancestor]] of hominids and African apes was characterized by relatively little aggression between males and between groups. This is markedly different from social patterns in common chimpanzees, among which intermale and intergroup aggression are typically high. Researchers in a 2009 study said that this condition "compromises the living chimpanzee as a behavioral model for the ancestral hominid condition."<ref name="Suwa_2009b"/> Bonobo canine size and canine sexual dimorphism more closely resembles that of ''A. ramidus'', and as a result, bonobos are now suggested as a behavioural model.<ref>{{Cite web|title=Science X Network :: Phys.org, Medical Xpress, Tech Xplore|url=https://sciencex.com/wire-news/399727984/canine-sexual-dimorphism-in-ardipithecus-ramidus-is-estimated.html|access-date=2021-12-01|website=sciencex.com}}</ref>

''A. ramidus'' existed more recently than the [[most recent common ancestor]] of humans and chimpanzees ([[chimpanzee–human last common ancestor|CLCA or ''Pan''-''Homo'' LCA]]) and thus is not fully representative of that common ancestor. Nevertheless, it is in some ways unlike chimpanzees, suggesting that the common ancestor differs from the modern chimpanzee. After the chimpanzee and human lineages diverged, both underwent substantial evolutionary change. Chimp feet are specialized for grasping trees; ''A. ramidus'' feet are better suited for walking. The canine teeth of ''A. ramidus'' are smaller, and equal in size between males and females, which suggests reduced male-to-male conflict, increased pair-bonding, and increased parental investment. "Thus, fundamental reproductive and social behavioral changes probably occurred in hominids long before they had enlarged brains and began to use stone tools," the research team concluded.<ref name="AndThePaleobiology" />

=== Ardi ===
{{Main|Ardi}}
On October 1, [[2009 in science|2009]], paleontologists formally announced the discovery of the relatively complete ''A. ramidus'' fossil skeleton first unearthed in 1994. The fossil is the remains of a small-brained 50-kilogram (110&nbsp;lb) female, nicknamed "Ardi", and includes most of the skull and teeth, as well as the pelvis, hands, and feet.<ref name="NewKind" /> It was discovered in Ethiopia's harsh [[Afar Region|Afar desert]] at a site called [[Aramis, Ethiopia|Aramis]] in the Middle Awash region. Radiometric dating of the layers of volcanic ash encasing the deposits suggest that Ardi lived about 4.3-4.5 million years ago. This date, however, has been questioned by others. Fleagle and Kappelman suggest that the region in which Ardi was found is difficult to date radiometrically, and they argue that Ardi should be dated at 3.9 million years.<ref name="10.1038/nature09709">{{cite journal |doi=10.1038/376558b0 |pmid=7503900 |last1=Kappelman |first1= John| last2=Fleagle |first2= John G.| date=1995 |title=Age of early hominids |journal=[[Nature (journal)|Nature]] |volume=376 |issue=6541| pages=558–559 |bibcode=1995Natur.376..558K |s2cid=5527405 }}</ref>

The fossil is regarded by its describers as shedding light on a stage of human evolution about which little was known, more than a million years before [[Lucy (Australopithecus)|Lucy]] (''Australopithecus afarensis''), the iconic early human ancestor candidate who lived 3.2 million years ago, and was discovered in 1974 just {{convert|74|km|mi|abbr=on}} away from Ardi's discovery site. However, because the "Ardi" skeleton is no more than 200,000 years older than the earliest fossils of ''Australopithecus'', and may in fact be younger than they are,<ref name="10.1038/nature09709"/> some researchers doubt that it can represent a direct ancestor of ''Australopithecus''.

Some researchers infer from the form of her pelvis and limbs and the presence of her [[Abduction (kinesiology)|abductable]] [[hallux]], that "Ardi" was a [[facultative biped]]: [[biped]]al when moving on the ground, but [[quadruped]]al when moving about in tree branches.<ref name="AndThePaleobiology">{{cite journal |doi=10.1126/science.1175802 |pmid=19810190 |title=Ardipithecus ramidus and the Paleobiology of Early Hominids |journal=Science |volume=326 |issue=5949 |pages=75–86 |year=2009 |last1=White |first1=T. D. |last2=Asfaw |first2=B. |last3=Beyene |first3=Y. |last4=Haile-Selassie |first4=Y. |last5=Lovejoy |first5=C. O. |last6=Suwa |first6=G. |last7=Woldegabriel |first7=G. |bibcode=2009Sci...326...75W |s2cid=20189444 }}</ref><ref>{{cite web|url= http://news.nationalgeographic.com/news/2009/10/091001-oldest-human-skeleton-ardi-missing-link-chimps-ardipithecus-ramidus.html |archive-url= https://web.archive.org/web/20091004002647/http://news.nationalgeographic.com/news/2009/10/091001-oldest-human-skeleton-ardi-missing-link-chimps-ardipithecus-ramidus.html |url-status= dead |archive-date= October 4, 2009 |title=Oldest Skeleton of Human Ancestor Found |first=Jamie |last=Shreeve |publisher=[[National Geographic magazine]] |date=2009-10-01 |access-date=March 18, 2017 }}</ref><ref>{{cite journal|url= https://www.science.org/content/article/ancient-skeleton-may-rewrite-earliest-chapter-human-evolution |title=Ancient Skeleton May Rewrite Earliest Chapter of Human Evolution |first=Ann |last=Gibbons |journal=[[Science (journal)|Science]] |date=October 2009 |access-date=March 18, 2017 }}</ref> ''A. ramidus'' had a more primitive walking ability than later hominids, and could not walk or run for long distances.<ref>{{cite news|url= http://news.bbc.co.uk/1/hi/sci/tech/8285180.stm |work=BBC News |title=Fossil finds extend human story |date=October 1, 2009 |first=Jonathan |last=Amos}}</ref> The teeth suggest [[omnivory]], and are more generalised than those of modern apes.<ref name="AndThePaleobiology" />

<gallery>
File:Ardipithecus (finger bones).jpg|Casts of Ardi's finger bones.
</gallery>

== ''Ardipithecus kadabba'' ==
{{Main|Ardipithecus kadabba}}
[[Image:Ardipithecus kadabba fossils.jpg|thumb|250px|''Ardipithecus kadabba'' fossils]]
''Ardipithecus kadabba'' is "known only from teeth and bits and pieces of skeletal bones",<ref name="NewKind">{{cite journal |doi=10.1126/science.326_36 |pmid=19797636 |title=A New Kind of Ancestor: Ardipithecus Unveiled |journal=Science |volume=326 |issue=5949 |pages=36–40 |year=2009 |last1=Gibbons |first1=A. |url= http://doc.rero.ch/record/211155/files/PAL_E4410.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://doc.rero.ch/record/211155/files/PAL_E4410.pdf |archive-date=2022-10-09 |url-status=live |bibcode=2009Sci...326...36G }}</ref> and is dated to approximately 5.6 million years ago.<ref name="AndThePaleobiology" /> It has been described as a "probable [[chronospecies]]" (i.e. ancestor) of ''A. ramidus''.<ref name="AndThePaleobiology" /> Although originally considered a subspecies of ''A. ramidus'', in 2004 anthropologists [[Yohannes Haile-Selassie]], [[Gen Suwa]], and [[Tim D. White]] published an article elevating ''A. kadabba'' to species level on the basis of newly discovered teeth from [[Ethiopia]]. These teeth show "primitive morphology and wear pattern" which demonstrate that ''A. kadabba'' is a distinct species from ''A. ramidus''.<ref name="MioceneTeeth">{{cite journal |doi=10.1126/science.1092978 |pmid=15001775 |title=Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution |journal=Science |volume=303 |issue=5663 |pages=1503–5 |year=2004 |last1=Haile-Selassie |first1=Y. |last2=Suwa |first2=Gen |last3=White |first3=Tim D. |bibcode=2004Sci...303.1503H |s2cid=30387762 }}</ref>

The specific name comes from the [[Afar language|Afar]] word for "basal family ancestor".<ref name="EllisNTB">{{cite book |last=Ellis |first=Richard |author-link=Richard Ellis (biologist) |title=No Turning Back: The Life and Death of Animal Species|url= https://archive.org/details/noturningbacklif00elli |url-access=registration |publisher=Harper Perennial |date=2004 |location=New York |pages=[https://archive.org/details/noturningbacklif00elli/page/92 92] |isbn =978-0-06-055804-8 }}</ref>

== Classification ==
Due to several shared characteristics with chimpanzees, its closeness to ape divergence period, and due to its fossil incompleteness, the exact position of ''Ardipithecus'' in the fossil record is a subject of controversy.<ref>{{cite journal |doi=10.1038/nature09709 |pmid=21331035 |last1=Wood |first1= Bernard| last2=Harrison |first2= Terry| date=2011 |title=The evolutionary context of the first hominins |journal=[[Nature (journal)|Nature]] |volume=470 |pages=347–35 |bibcode=2011Natur.470..347W |issue=7334 |s2cid=4428052 }}</ref> Primatologist [[Esteban Sarmiento]] had systematically compared and concluded that there is not sufficient anatomical evidence to support an exclusively human lineage. Sarmiento noted that ''Ardipithecus'' does not share any characteristics exclusive to humans, and some of its characteristics (those in the wrist and basicranium) suggest it diverged from humans prior to the [[human–gorilla last common ancestor]].<ref>{{cite journal |doi=10.1126/science.1184148 |pmid=20508113 |title=Comment on the Paleobiology and Classification of ''Ardipithecus ramidus'' |journal=Science |volume=328 |issue=5982 |pages=1105; author reply 1105 |year=2010 |last1=Sarmiento |first1=E. E. |bibcode=2010Sci...328.1105S |doi-access= }}</ref> His comparative (narrow [[allometry]]) study in 2011 on the molar and body segment lengths (which included living primates of similar body size) noted that some dimensions including short upper limbs, and [[metacarpals]] are reminiscent of humans, but other dimensions such as long toes and relative molar surface area are [[great ape]]-like. Sarmiento concluded that such length measures can change back and forth during evolution and are not very good indicators of relatedness ([[homoplasy]]).<ref name=Sarmiento2011>{{cite journal |doi=10.1016/j.jchb.2011.01.003 |pmid=21388620 |title=Behavioral and phylogenetic implications of a narrow allometric study of ''Ardipithecus ramidus'' |journal=HOMO |volume=62 |issue=2 |pages=75–108 |year=2011 |last1=Sarmiento |first1=E.E. |last2=Meldrum |first2=D.J. }}</ref>

However, some later studies still argue for its classification in the human lineage. In 2014, it was reported that the hand bones of ''Ardipithecus'', ''[[Australopithecus sediba]]'' and ''[[A. afarensis]]'' have the third metacarpal [[Styloid process (radius)|styloid process]], which is absent in other apes.<ref>{{cite journal |doi=10.1073/pnas.1316014110 |pmid=24344276 |pmc=3890866 |title=Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology |journal=Proceedings of the National Academy of Sciences |volume=111 |issue=1 |pages=121–4 |year=2013 |last1=Ward |first1=C. V. |last2=Tocheri |first2=M. W. |last3=Plavcan |first3=J. M. |last4=Brown |first4=F. H. |last5=Manthi |first5=F. K. |bibcode=2014PNAS..111..121W |doi-access=free }}</ref> Unique brain organisations (such as lateral shift of the carotid foramina, mediolateral abbreviation of the lateral [[Tympanic cavity|tympanic]], and a shortened, trapezoidal [[Occipital lobe|basioccipital]] element) in ''Ardipithecus'' are also found only in the ''Australopithecus'' and ''Homo''.<ref>{{cite journal |doi=10.1073/pnas.1322639111 |pmid=24395771 |pmc=3903226 |title=Ardipithecus ramidus and the evolution of the human cranial base |journal=Proceedings of the National Academy of Sciences |volume=111 |issue=3 |pages=948–53 |year=2014 |last1=Kimbel |first1=W. H. |last2=Suwa |first2=G. |last3=Asfaw |first3=B. |last4=Rak |first4=Y. |last5=White |first5=T. D. |bibcode=2014PNAS..111..948K |doi-access=free }}</ref> Comparison of the tooth root morphology with those of the earlier ''[[Sahelanthropus]]'' also indicated strong resemblance, also pointing to inclusion to the human line.<ref>{{cite journal |doi=10.1002/ajpa.22400 |pmid=24242778 |title=Subocclusal dental morphology of ''Sahelanthropus tchadensis'' and the evolution of teeth in hominins |journal=American Journal of Physical Anthropology |volume=153 |issue=1 |pages=116–23 |year=2014 |last1=Emonet |first1=Edouard-Georges |last2=Andossa |first2=Likius |last3=Taïsso Mackaye |first3=Hassane |last4=Brunet |first4=Michel }}</ref>

[[Evolutionary tree]] according to a 2019 study:<ref name="Parins2019">{{cite journal |last1=Parins-Fukuchi |first1=C. |last2=Greiner |first2=E. |last3=MacLatchy |first3=L. M. |last4=Fisher |first4=D. C. |year=2019 |title=Phylogeny, ancestors and anagenesis in the hominin fossil record |url=https://www.biorxiv.org/content/biorxiv/early/2018/10/05/434894.full.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.biorxiv.org/content/biorxiv/early/2018/10/05/434894.full.pdf |archive-date=2022-10-09 |url-status=live |journal=Paleobiology |volume=45 |issue=2 |pages=378–393 |doi=10.1017/pab.2019.12 |bibcode=2019Pbio...45..378P |s2cid=196659329}}</ref>

{{clade| style=font-size:85%;line-height:85%
|label1=[[Hominini]]
|1={{clade
 |1=[[Chimpanzee]]
 |label2=''[[Sahelanthropus]]''
 |2={{clade
  |1={{clade
   |1='''''Ardipithecus'''''
   |label2=''[[Australopithecus anamensis|Au. anamensis]]''
   |2=''[[Australopithecus afarensis|Au. afarensis]]''
   }}
  |2={{clade
   |label1=''[[Paranthropus]]''
   |1={{clade
    |1=''[[Paranthropus aethiopicus|P. aethiopicus]]''
    |2={{clade
     |1=''[[Paranthropus boisei|P. boisei]]''
     |2=''[[Paranthropus robustus|P. robustus]]''
     }}
    }}
   |2={{clade
    |label2=''[[Australopithecus garhi|Au. garhi]]''
    |1=''[[Australopithecus africanus|Au. africanus]]''
    |2={{clade
     |1=''[[Homo floresiensis|H. floresiensis]]''
     |2={{clade
      |1=''[[Australopithecus sediba|Au. sediba]]''
      |2={{clade
       |1=''[[Homo habilis|H. habilis]]''
       |2=Other ''[[Homo]]''
       }}
      }}
     }}
    }}
}}}}}}}}

== Paleobiology ==
The ''Ardipithecus'' length measures are good indicators of function and together with dental isotope data and the fauna and flora from the fossil site indicate ''Ardipithecus'' was mainly a terrestrial quadruped collecting a large portion of its food on the ground. Its arboreal behaviors would have been limited and suspension from branches solely from the upper limbs rare.<ref name=Sarmiento2011/> A comparative study in 2013 on carbon and oxygen stable isotopes within modern and fossil [[tooth enamel]] revealed that ''Ardipithecus'' fed both [[Arboreal locomotion|arboreally]] (on trees) and on the ground in a more open habitat, unlike chimpanzees.<ref>{{cite journal |doi=10.1098/rspb.2013.2324 |pmid=24197413 |pmc=3826229 |title=Chimpanzee fauna isotopes provide new interpretations of fossil ape and hominin ecologies |journal=Proceedings of the Royal Society B: Biological Sciences |volume=280 |issue=1773 |pages=20132324 |year=2013 |last1=Nelson |first1=S. V. }}</ref>

In 2015, Australian anthropologists Gary Clark and Maciej Henneberg said that ''Ardipithecus'' adults have a facial anatomy more similar to chimpanzee subadults than adults, with a less-projecting face and smaller canines (large canines in primate males are used to compete within mating hierarchies), and attributed this to a decrease in craniofacial growth in favour of brain growth. This is only seen in humans, so they argued that the species may show the first trend towards human social, parenting and sexual psychology.<ref name="Clark & Henneberg 2015"/> Previously, it was assumed that such ancient human ancestors behaved much like chimps, but this is no longer considered to be a viable comparison.<ref>{{cite journal |doi=10.1146/annurev-anthro-092611-145815 |ssrn=2158266 |title=Human Evolution and the Chimpanzee Referential Doctrine |journal=Annual Review of Anthropology |volume=41 |pages=119–38 |year=2012 |last1=Sayers |first1=Ken |last2=Raghanti |first2=Mary Ann |last3=Lovejoy |first3=C. Owen }}</ref> This view has yet to be corroborated by more detailed studies of the growth of ''A.ramidus''. The study also provides support for Stephen Jay Gould's theory in [[Ontogeny and Phylogeny (book)|''Ontogeny and Phylogeny'']] that the paedomorphic (childlike) form of early hominin craniofacial morphology results from dissociation of growth trajectories.

Clark and Henneberg also argued that such shortening of the skull—which may have caused a descension of the [[larynx]]—as well as lordosis—allowing better movement of the larynx—increased vocal ability, significantly pushing back the [[origin of language]] to well before the evolution of ''Homo''. They argued that self domestication was aided by the development of vocalization, living in a pro-social society. They conceded that chimps and ''A. ramidus'' likely had the same vocal capabilities, but said that ''A. ramidus'' made use of more complex vocalizations, and vocalized at the same level as a human infant due to [[selective pressure]] to become more social. This would have allowed their society to become more complex. They also noted that the base of the skull stopped growing with the brain by the end of juvenility, whereas in chimps it continues growing with the rest of the body into adulthood; and considered this evidence of a switch from a gross skeletal anatomy trajectory to a neurological development trajectory due to selective pressure for sociability. Nonetheless, their conclusions are highly speculative.<ref>{{cite journal|first1=G.|last1=Clark|first2=M.|last2=Henneberg|year=2017|title=''Ardipithecus ramidus'' and the evolution of language and singing: An early origin for hominin vocal capability|journal=Homo|volume=68|issue=2|pages=101–121|doi=10.1016/j.jchb.2017.03.001|pmid=28363458}}</ref><ref name="Clark & Henneberg 2015">{{cite journal |doi=10.1515/anre-2015-0009 |title=The life history of Ardipithecus ramidus: A heterochronic model of sexual and social maturation |journal=Anthropological Review |volume=78 |issue=2 |pages=109–132|year=2015 |last1=Clark |first1=Gary |last2=Henneberg |first2=Maciej |doi-access=free }}</ref>

According to [[Scott Simpson (anthropologist)|Scott Simpson]], the Gona Project's [[biological anthropology|physical anthropologist]], the fossil evidence from the [[Middle Awash]] indicates that both ''A. kadabba'' and ''A. ramidus'' lived in "a mosaic of woodland and grasslands with lakes, swamps and springs nearby," but further research is needed to determine which habitat ''Ardipithecus'' at Gona preferred.<ref name="stoneageinstitute.org" />


== See also ==
{{div col|colwidth=30em}}
* ''[[Australopithecus]]''
* ''[[Paranthropus]]''
* ''[[Graecopithecus]]''
* [[List of human evolution fossils]]
* ''[[Orrorin]]''
* ''[[Sahelanthropus]]''
{{div col end}}

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

== External links ==
{{Wikispecies}}
{{Commons category|Ardipithecus}}
* [http://www.sciencemag.org/ardipithecus/ Science Magazine: ''Ardipithecus'' special] (requires free registration)
* The Smithsonian Institution's Human Origins Program:
** [http://humanorigins.si.edu/evidence/human-fossils/species/ardipithecus-kadabba Ardipithecus kadabba]
** [http://humanorigins.si.edu/evidence/human-fossils/species/ardipithecus-ramidus Ardipithecus ramidus]
* [http://www.archaeologyinfo.com/ardipithecusramidus.htm ''Ardipithecus ramidus''] {{Webarchive|url=https://web.archive.org/web/20120308171256/http://archaeologyinfo.com/ardipithecus-ramidus/ |date=2012-03-08 }} at Archaeology info
* [https://web.archive.org/web/20091004002759/http://ngm.nationalgeographic.com/human-evolution/human-ancestor ''Explore Ardipithecus''] at [[National Geographic Magazine|NationalGeographic.com]]
* [https://www.science.org/doi/full/10.1126/science.1175802?sid=0e89e15f-0594-40ef-9dce-2b9b9f48d9e6 ''Ardipithecus ramidus'' - Science Journal Article]
* [https://web.archive.org/web/20130228131344/http://dsc.discovery.com/tv/ardipithecus/ardipithecus.html Discovering Ardi - Discovery Channel]
* [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – [[Smithsonian Institution|Smithsonian]], [[National Museum of Natural History]] (August 2016).

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[[Category:Miocene primates]]
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[[Category:Prehistoric primate genera]]
[[Category:Pliocene primates]]
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[[Category:Prehistoric Ethiopia]]
[[Category:Miocene genus first appearances]]
[[Category:Zanclean extinctions]]
[[Category:Neogene mammals of Africa]]