Editing Ardipithecus (section)

== ''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 name=":0"/>

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 |date=2005-01-10 |title=New Fossil Hominids of Ardipithecus ramidus from Gona, Afar, Ethiopia |url=http://www.stoneageinstitute.org/news/gona_nature_paper.shtml#1 |archive-url=https://web.archive.org/web/20080624005441/http://www.stoneageinstitute.org/news/gona_nature_paper.shtml |archive-date=2008-06-24 |access-date=2009-01-30 |website=stoneageinstitute.org}}</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 [[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 name=":0"/>

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 {{Convert|50|kg|adj=on}} 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 to 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 {{cvt|74|km}} 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>