View source for Ardipithecus ramidus

{{good article}}
{{short description|Extinct hominin from Early Pliocene Ethiopia}}
{{Speciesbox
| fossil_range = [[Zanclean]] {{fossil range|4.5|4.32}}
| image = Ardipithecus ramidus.jpg
| image_alt = A skull
| image_caption = ''A. ramidus'' at the [[Museo Nacional de Ciencias Naturales]]
| genus = Ardipithecus
| species = ramidus
| authority = ([[Tim D. White|White]], [[Gen Suwa|Suwa]] & [[Berhane Asfaw|Asfaw]], 1994)
| synonyms = *''Australopithecus ramidus''
}}

'''''Ardipithecus ramidus''''' is a species of [[australopithecine]] from the [[Afar region]] of [[Early Pliocene]] Ethiopia 4.4 million years ago (mya). ''A. ramidus'', unlike modern [[hominid]]s, has adaptations for both walking on two legs ([[biped]]ality) and life in the trees ([[arboreal]]ity). However, it would not have been as efficient at bipedality as [[human]]s, nor at arboreality as non-human [[great ape]]s. Its discovery, along with [[Miocene]] apes, has reworked academic understanding of the [[chimpanzee–human last common ancestor]] from appearing much like modern-day [[chimpanzee]]s, [[orangutan]]s and [[gorilla]]s to being a creature without a modern anatomical cognate.

The facial anatomy suggests that ''A. ramidus'' males were less aggressive than those of modern chimps, which is correlated to increased parental care and [[Monogamy in animals|monogamy]] in primates. It has also been suggested that it was among the earliest of human ancestors to use some proto-language, possibly capable of vocalizing at the same level as a human infant. This is based on evidence of human-like skull architecture, cranial base angle and vocal tract dimensions, all of which in ''A. ramidus'' are paedomorphic when compared to chimpanzees and bonobos. This suggests the trend toward paedomorphic or juvenile-like form evident in human evolution, may have begun with ''A. ramidus''. Given these unique features, it has been argued that in ''A. ramidus'' we may have the first evidence of human-like forms of social behaviour, vocally mediated sociality as well as increased levels of prosociality via the process of self-domestication—all of which seem to be associated with the same underlying changes in skull architecture. ''A. ramidus'' appears to have inhabited [[woodland]] and [[bushland]] corridors between savannas, and was a generalized [[omnivore]].

==Taxonomy==
[[Image:Map of the fossil sites of the earliest hominids (35.8-3.3M BP).svg|thumb|left|Map showing discovery locations of various [[australopithecine]]s]]
The first remains were described in 1994 by American anthropologist [[Tim D. White]], Japanese paleoanthropologist [[Gen Suwa]], and Ethiopian paleontologist [[Berhane Asfaw]]. The [[holotype specimen]], ARA-VP-6/1, comprised an associated set of 10 teeth; and there were 16 other [[paratype]]s identified, preserving also skull and arm fragments. These were unearthed in the 4.4-million-year-old (Ma) deposits of the [[Afar region]] in [[Aramis, Ethiopia]] from 1992 to 1993, making them the oldest hominin remains at the time, surpassing ''[[Australopithecus afarensis]]''. They initially classified it as ''Australopithecus ramidus'', the [[species name]] deriving from the [[Afar language]] ''ramid'' "root".<ref name=White1994>{{Cite journal|last1=White |first1=T. D.|author-link1=Tim D. White|last2=Suwa |first2=G.|author-link2=Gen Suwa|last3=Asfaw |first3=B. |author-link3=Berhane Asfaw|title=''Australopithecus ramidus'', a new species of early hominid from Aramis, Ethiopia |journal=Nature |volume=371 |pages=306–312 |year=1994 |pmid=8090200 |doi=10.1038/371306a0|url=http://www2.ku.edu/~lba/courses/articles/White%20ramadis94.pdf |bibcode=1994Natur.371..306W|issue=6495 |s2cid=4347140|url-status=dead |archive-url=https://web.archive.org/web/20130413081635/http://www2.ku.edu/~lba/courses/articles/White%20ramadis94.pdf |archive-date=2013-04-13 }}</ref> In 1995, they made a [[corrigendum]] recommending it be split off into a separate genus, ''Ardipithecus''; the name stems from Afar ''ardi'' "ground" or "floor".<ref>{{Cite journal|last1=White |first1=T. D.|author-link1=Tim D. White|last2=Suwa |first2=G.|author-link2=Gen Suwa|last3=Asfaw |first3=B. |author-link3=Berhane Asfaw|title=Corrigendum: ''Australopithecus ramidus'', a new species of early hominid from Aramis, Ethiopia |journal=Nature |volume=375 |page=88 |year=1995 |doi=10.1038/375088a0|issue=6526 |pmid=7677838|doi-access=free }}</ref> The 4.4-million-year-old female ARA-VP 6/500 ("[[Ardi]]") is the most complete specimen.<ref name=White2015/>

Fossils from at least nine ''A. ramidus'' individuals at [[As Duma]], [[Gona, Ethiopia|Gona Western Margin]], Afar, were unearthed from 1993 to 2003. The fossils were dated to between 4.32 and 4.51 million years ago.<ref>{{cite journal|first1=S.|last1=Semaw|first2=S. W.|last2=Simpson|display-authors=et al.|year=2005|title=Early Pliocene hominids from Gona, Ethiopia|journal=Nature|volume=433|issue=7023|pages=301–305|doi=10.1038/nature03177|pmid=15662421|bibcode=2005Natur.433..301S|s2cid=4431031|url=http://doc.rero.ch/record/15296/files/PAL_E2595.pdf }}</ref>

In 2001, 6.5- to 5.5-million-year-old fossils from the [[Middle Awash]] were classified as a subspecies of ''A. ramidus'' by Ethiopian paleoanthropologist [[Yohannes Haile-Selassie]].<ref name=Haile2001>{{cite journal|first=Y.|last=Haile-Selassie|author-link=Yohannes Haile-Selassie|year=2001|title=Late Miocene hominids from the Middle Awash, Ethiopia|journal=Nature|volume=42|issue=6843|pages=179–181|doi=10.1038/35084063|pmid=11449272|bibcode=2001Natur.412..178H|s2cid=4432082}}</ref> In 2004, Haile-Selassie, Suwa and White split it off into its own species, ''[[A. kadabba]]''.<ref>{{cite journal |last1=Haile-Selassie |first1=Y.|author-link1=Yohannes Haile-Selassie|last2=Suwa|first2=G.|author-link2=Gen Suwa|last3=White|first3=T. D.|author-link3=Tim D. White|date=2004 |title=Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution |journal=Science |volume=303 |issue=5663 |pages=1503–1505 |doi=10.1126/science.1092978 |pmid=15001775 |bibcode = 2004Sci...303.1503H |s2cid=30387762}}</ref> ''A. kadabba'' is considered to have been the direct ancestor of ''A. ramidus'', making ''Ardipithecus'' a [[chronospecies]].<ref name=Lovejoy2014>{{cite journal|first=C. O.|last=Lovejoy|author-link=Owen Lovejoy (anthropologist)|year=2014|title=''Ardipithecus'' and Early Human Evolution in Light of Twenty-First-Century Developmental Biology|journal=Journal of Anthropological Research|volume=70|issue=3|pages=337–363|doi=10.3998/jar.0521004.0070.301|jstor=24394231|s2cid=84197134}}</ref>

The exact [[affinity (taxonomy)|affinities]] of ''Ardipithecus'' have been debated. White, in 1994, considered ''A. ramidus'' to have been more closely related to [[human]]s than chimpanzees, though noting it to be the most [[ape]]-like fossil hominin to date.<ref name=White1994/> In 2001, French paleontologist [[Brigitte Senut]] and colleagues aligned it more closely to [[chimpanzee]]s,<ref>{{cite journal|first1=B.|last1=Senut|first2=M.|last2=Pickford|first3=D.|last3=Gommery|display-authors=et al.|year=2001|title=Premier hominidé du Miocène (formation de Lukeino, Kenya)|trans-title=First hominid from the Miocene (Lukeino Formation, Kenya)|language=fr|journal=Comptes Rendus de l'Académie des Sciences|volume=332|issue=2|pages=137–144|doi=10.1016/S1251-8050(01)01529-4|bibcode=2001CRASE.332..137S|s2cid=14235881 }}</ref> but this has been refuted.<ref name=Haile2001/> In 2009, White and colleagues reaffirmed the position of ''Ardipithecus'' as more closely related to modern humans based on dental similarity, a short [[base of the skull]], and adaptations to [[biped]]ality.<ref name="AndThePaleobiology"/> In 2011, primatologist [[Esteban Sarmiento]] said that there is not enough evidence to assign ''Ardipithecus'' to [[Hominini]] (comprising both humans and chimps),<ref name=Sarmiento2011/> but its closer affinities to humans have been reaffirmed in following years.<ref>{{cite journal|first1=W. H.|last1=Kimbel|first2=G.|last2=Suwa|author-link2=Gen Suwa|first3=B.|last3=Asfaw|author-link3=Berhane Asfaw|first4=Y.|last4=Rak|first5=T. D.|last5=White|author-link5=Tim D. White|year=2014|title=''Ardipithecus ramidus'' and the evolution of the human cranial base|journal=Proceedings of the National Academy of Sciences|volume=111|issue=3|pages=948–953|doi=10.1073/pnas.1322639111|pmc=3903226|pmid=24395771|bibcode=2014PNAS..111..948K|doi-access=free}}</ref> White and colleagues consider it to have been closely related to or the ancestor of the temporally close ''[[Australopithecus anamensis]]'', which was the ancestor to ''[[Au. afarensis]]''.<ref name=White2015/>

{{African hominin timeline}}

Before the discovery of ''Ardipithecus'' and other pre-''Australopithecus'' hominins, it was assumed that the [[chimpanzee–human last common ancestor]] and preceding apes appeared much like modern-day [[chimpanzee]]s, [[orangutan]]s and [[gorilla]]s, which would have meant these three changed very little over millions of years. Their discovery led to the postulation that modern great apes, much like humans, evolved several specialized adaptations to their environment (have highly derived [[synapomorphy and apomorphy|morphologies]]), and their ancestors were comparatively poorly adapted to [[suspensory behavior]] or knuckle walking, and did not have such a specialized diet. Also, the origins of bipedality were thought to have occurred due to a switch from a forest to a savanna environment, but the presence of bipedal pre-''Australopithecus'' hominins in [[woodland]]s has called this into question,<ref name=Lovejoy2009c/> though they inhabited wooded corridors near or between savannas. It is also possible that ''Ardipithecus'' and pre-''Australopithecus'' were random offshoots of the hominin line.<ref name=Cerling2010/>

==Description==
[[File:Ardipithecus Gesamt1.jpg|thumb|left|Reconstruction of ''Ardipithecus'' skeleton]]
Assuming subsistence was primarily sourced from climbing in trees, ''A. ramidus'' may not have exceeded {{cvt|35–60|kg}}. "Ardi," a larger female specimen, was estimated to have stood {{cvt|117–124|cm|ftin|sigfig=1}} and weighed {{cvt|51|kg}} based on comparisons with large-bodied female apes.<ref>{{cite journal|first1=C. O.|last1=Lovejoy|author-link1=Owen Lovejoy (anthropologist)|first2=G.|last2=Suwa|author-link2=Gen Suwa|first3=S. W.|last3=Simpson|first4=J. H.|last4=Matternes|first5=T. D.|last5=White|author-link5=Tim D. White|year=2009|title=The Great Divides: ''Ardipithecus ramidus'' Reveals the Postcrania of Our Last Common Ancestors with African Apes|journal=Science|volume=326|issue=5949|pages=73–106|doi=10.1126/science.1175833|bibcode=2009Sci...326..100L|pmid=19810199|s2cid=19629241}}</ref> Unlike the later ''Australopithecus'' but much like chimps and humans, males and females were about the same size.<ref name=White2015/>

''A. ramidus'' had a small brain, measuring {{cvt|300–350|cc}}. This is slightly smaller than a modern [[bonobo]] or chimp brain, but much smaller than the brain of ''[[Australopithecus]]—''about {{cvt|400|–|550|cc}}—and roughly 20% the size of the modern human brain. Like chimps, the ''A. ramidus'' face was much more pronounced ([[Prognathism|prognathic]]) than modern humans.<ref name="Suwa_2009">{{cite journal | title=The ''Ardipithecus ramidus'' skull and its implications for hominid origins | journal=Science | last1=Suwa | first1=G.|author-link1=Gen Suwa|year= 2009| volume=326 | issue=5949 | pages=68, 68e1–68e7 | doi=10.1126/science.1175825 | last2=Asfaw | first2=B. |author-link2=Berhane Asfaw| last3=Kono | first3=R. T. | last4=Kubo | first4=D. | last5=Lovejoy | first5=C. O.|author-link5=Owen Lovejoy (anthropologist)| last6=White | first6=T. D. |author-link6=Tim D. White| pmid=19810194|bibcode = 2009Sci...326...68S | s2cid=19725410 |display-authors=etal| url=http://doc.rero.ch/record/211453/files/PAL_E4442.pdf }}</ref> The size of the upper [[canine tooth]] in ''A. ramidus'' males was not distinctly different from that of females (only 12% larger), in contrast to the [[sexual dimorphism]] observed in chimps where males have significantly larger and sharper upper canines than females.<ref name=White2015/><ref name="Suwa_2009b">{{cite journal | title=Paleobiological implications of the ''Ardipithecus ramidus'' dentition | journal=Science | year=2009| last1=Suwa | first1=G. |author-link1=Gen Suwa| volume=326 | issue=5949 | pages=69, 94–99 | doi=10.1126/science.1175824 | last2=Kono | first2=R. T. | last3=Simpson | first3=S. W. | last4=Asfaw | first4=B. |author-link4=Berhane Asfaw| last5=Lovejoy | first5=C. O. |author-link5=Owen Lovejoy (anthropologist)| last6=White | first6=T. D. |author-link6=Tim D. White| pmid=19810195|bibcode = 2009Sci...326...94S | s2cid=3744438 |display-authors=etal| url=http://doc.rero.ch/record/211460/files/PAL_E4443.pdf }}</ref>

''A. ramidus'' feet are better suited for walking than chimps. However, like non-human great apes, but unlike all previously recognized human ancestors, it had a grasping big toe adapted for locomotion in the trees (an [[arboreal]] lifestyle), though it was likely not as specialized for grasping as it is in modern great apes.<ref name="AndThePaleobiology"/><ref name=Lovejoy2009b/> Its [[tibia]]l and [[tarsus (skeleton)|tarsal]] lengths indicate a leaping ability similar to bonobos.<ref name=Sarmiento2011>{{cite journal|first1=E. E.|last1=Sarmiento|author-link1=Esteban Sarmiento|first2=D. J.|last2=Meldrum|year=2011|title=Behavioral and phylogenetic implications of a narrow allometric study of ''Ardipithecus ramidus''|journal=HOMO|volume=62|issue=2|pages=75–108|doi=10.1016/j.jchb.2011.01.003|pmid=21388620}}</ref> It lacks any characters suggestive of specialized [[suspensory behaviour|suspension]], vertical climbing, or [[knuckle walking]]; and it seems to have used a method of locomotion unlike any modern great ape, which combined arboreal [[palmigrade|palm walking]] clambering and a form of bipedality more primitive than ''Australopithecus''. The discovery of such unspecialized locomotion led American anthropologist [[Owen Lovejoy (anthropologist)|Owen Lovejoy]] and colleagues to postulate that the chimpanzee–human last common ancestor used a similar method of locomotion.<ref name="AndThePaleobiology"/><ref>{{cite journal|first1=C. O.|last1=Lovejoy|author-link1=Owen Lovejoy (anthropologist)|first2=S. W.|last2=Simpson|first3=T. D.|last3=White|author-link3=Tim D. White|first4=B.|last4=Asfaw|author-link4=Berhane Asfaw|first5=G.|last5=Suwa|author-link5=Gen Suwa|year=2009|title=Careful Climbing in the Miocene: The Forelimbs of ''Ardipithecus ramidus'' and Humans Are Primitive|journal=Science|volume=326|issue=5949|pages=70–70e8|doi=10.1126/science.1175827|pmid=19810196|bibcode=2009Sci...326...70L|s2cid=37251630|url=http://doc.rero.ch/record/211452/files/PAL_E4441.pdf}}</ref>

The upper pelvis (distance from the [[sacrum]] to the [[hip joint]]) is shorter than in any known ape. It is inferred to have had a long [[lumbar vertebra]]l series, and [[lordosis]] (human curvature of the spine), which are adaptations for bipedality. However, the legs were not completely aligned with the torso (were anterolaterally displaced), and ''Ardipithecus'' may have relied more on its [[quadriceps]] than [[hamstrings]] which is more effective for climbing than walking.<ref name=Lovejoy2014/><ref name=Lovejoy2009a>{{cite journal|first1=C. O.|last1=Lovejoy|author-link1=Owen Lovejoy (anthropologist)|first2=G.|last2=Suwa|author-link2=Gen Suwa|first3=L.|last3=Spurlock|first4=B.|last4=Asfaw|author-link4=Berhane Asfaw|first5=T. D.|last5=White|author-link5=Tim D. White|year=2009|title=The Pelvis and Femur of ''Ardipithecus ramidus'': The Emergence of Upright Walking|journal=Science|volume=326|issue=5949|pages=71–71e6|doi=10.1126/science.1175831|pmid=19810197|bibcode=2009Sci...326...71L|s2cid=19505251|url=http://doc.rero.ch/record/211462/files/PAL_E4444.pdf}}</ref> However, it lacked [[foot arch]]es and had to adopt a flat-footed stance. These would have made it less efficient at walking and running than ''Australopithecus'' and ''Homo''. It may not have employed a bipedal gait for very long time intervals.<ref name="White2015">{{cite journal|first1=T. D.|last1=White|author-link1=Tim D. White|first2=C. O.|last2=Lovejoy|first3=B.|last3=Asfaw|author-link3=Berhane Asfaw|first4=J. P.|last4=Carlson|first5=G.|last5=Suwa|author-link5=Gen Suwa|year=2015|title=Neither chimpanzee nor human, ''Ardipithecus'' reveals the surprising ancestry of both|journal=Proceedings of the National Academy of Sciences|volume=112|issue=16|pages=4877–4884|doi=10.1073/pnas.1403659111|pmc=4413341|pmid=25901308|bibcode=2015PNAS..112.4877W|doi-access=free}}</ref> It may have predominantly used palm walking on the ground,<ref>{{cite journal|first=T. C.|last=Prang|year=2019|title=The African ape-like foot of ''Ardipithecus ramidus'' and its implications for the origin of bipedalism|journal=eLife|volume=8|pages=e44433|doi=10.7554/eLife.44433|pmc=6491036|pmid=31038121 |doi-access=free }}</ref> Nonetheless, ''A. ramidus'' still had specialized adaptations for bipedality, such as a robust [[fibularis longus]] muscle used in pushing the foot off the ground while walking ([[plantarflexion]]),<ref name=Lovejoy2009b>{{cite journal|first1=C. O.|last1=Lovejoy|first2=B.|last2=Latimar|first3=G.|last3=Suwa|author-link3=Gen Suwa|first4=B.|last4=Asfaw|author-link4=Berhane Asfaw|first5=T. D.|last5=White|author-link5=Tim D. White|year=2011|title=Combining Prehension and Propulsion: The Foot of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=72–72e8|doi=10.1126/science.1175832|pmid=19810198|s2cid=26778544|url=http://doc.rero.ch/record/211468/files/PAL_E4445.pdf}}</ref> the big toe (though still capable of grasping) was used for pushing off, and the legs were aligned directly over the ankles instead of bowing out like in non-human great apes.<ref>{{cite journal|first1=S. W.|last1=Simpson|first2=N. E.|last2=Levin|first3=J.|last3=Quade|first4=M. J.|last4=Rogers|first5=S.|last5=Semaw|year=2019|title=''Ardipithecus ramidus'' postcrania from the Gona Project area, Afar Regional State, Ethiopia|journal=Journal of Human Evolution|volume=129|pages=1–45|doi=10.1016/j.jhevol.2018.12.005|pmid=30904038|s2cid=85500710|doi-access=free|bibcode=2019JHumE.129....1S }}</ref>

==Paleobiology==
[[File:Modell eines Schädels des Pan troglodytes (Schimpanse, weiblich).jpg|thumb|Chimp skull (note the large canines and elongated face)]]
The reduced canine size and reduced skull robustness in ''A. ramidus'' males (about the same size in males and females) is typically correlated with reduced male–male conflict, increased parental investment, and [[Monogamy in animals|monogamy]].<ref name=Lovejoy2014/><ref name="AndThePaleobiology">{{cite journal |last1=White |first1=T. D.|author-link1=Tim D. White |last2=Asfaw|first2=B.|author-link2=Berhane Asfaw|last3=Beyene|first3=Y.|last4=Haile-Selassie|first4=Y.|author-link4=Yohannes Haile-Selassie|last5=Lovejoy|first5=C. O.|author-link5=Owen Lovejoy (anthropologist)|last6=Suwa|first6=G.|author-link6=Gen Suwa|last7=WoldeGabriel|first7= G.|s2cid=20189444|author-link7=Giday WoldeGabriel|year=2009 |title=''Ardipithecus ramidus'' and the Paleobiology of Early Hominids |journal=[[Science (journal)|Science]] |volume=326 |issue=5949 |pages=75–86 |doi=10.1126/science.1175802 |pmid=19810190|bibcode = 2009Sci...326...75W }}</ref> Because of this, it is assumed that ''A. ramidus'' lived in a society similar to bonobos and [[ateline]] monkeys<ref name="Suwa_2009b"/> due to a process of [[self-domestication#in humans|self domestication]] (becoming more and more docile which allows for a more gracile build). Because a similar process is thought to have occurred with the comparatively docile bonobos from more aggressive chimps, ''A. ramidus'' society may have seen an increase in maternal care and female mate selection compared to its ancestors.<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> Alternatively, it is possible that increased male size is a derived trait instead of basal (it evolved later rather than earlier), and is a specialized adaptation in modern great apes as a response to a different and more physically exerting lifestyle in males than females rather than being tied to interspecific conflict.<ref name=Lovejoy2009c>{{cite journal|first=C. O.|last=Lovejoy|year=2009|title=Reexamining Human Origins in Light of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=74–74e8|doi=10.1126/science.1175834|bibcode=2009Sci...326...74L|pmid=19810200|s2cid=42790876|url=http://doc.rero.ch/record/211449/files/PAL_E4439.pdf}}</ref>

Australian anthropologists Gary Clark and [[Maciej Henneberg]] 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, as a means of non-violently dealing with conflict. 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 name="Clark & Henneberg 2015"/><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>

[[File:Nut cracking Ardipithecus.png|thumb|left|upright=1.1|Hypothetical restoration of a female ''Ardipithecus'' using a hammer and anvil to crack open a nut]]
American primatologist [[Craig Stanford]] postulated that ''A. ramidus'' behaved similarly to chimps, which frequent both the trees and the ground, have a [[polygyny in animals|polygynous]] society, hunt cooperatively, and are the most [[tool use by animals|technologically advanced non-human]].<ref>{{cite journal|first=C. B.|last=Stanford|author-link=Craig Stanford|year=2012|title=Chimpanzees and the Behavior of ''Ardipithecus ramidus''|journal=Annual Review of Anthropology|volume=41|pages=139–149|doi=10.1146/annurev-anthro-092611-145724}}</ref> However, Clark and Henneberg concluded that ''Ardipithecus'' cannot be compared to chimps, having been too similar to humans.<ref name="Clark & Henneberg 2015"/> According to French paleoprimatologist [[Jean-Renaud Boisserie]], the hands of ''Ardipithecus'' would have been dextrous enough to handle basic tools, though it has not been associated with any tools.<ref name=Boisserie2010>{{cite journal|first=J.-R.|last=Boisserie|year=2010|title=''Ardipithecus ramidus'' and the birth of humanity|journal=Annales d'Éthiopie|volume=25|pages=271–281|url=https://www.persee.fr/doc/ethio_0066-2127_2010_num_25_1_1420|doi=10.3406/ethio.2010.1420}}</ref>

The teeth of ''A. ramidus'' indicate that it was likely a generalized [[omnivore]] and [[frugivore|fruit eater]] which predominantly consumed [[C3 plant]]s in woodlands or [[gallery forest]]s. The teeth lacked adaptations for abrasive foods.<ref name="AndThePaleobiology"/><ref name=Sarmiento2011/><ref name="Suwa_2009b"/> Lacking the speed and agility of chimps and baboons, meat intake by ''Ardipithecus'', if done, would have been sourced from only what could have been captured by limited pursuit, or from scavenging carcasses.<ref>{{cite journal|first1=K.|last1=Sayers|first2=C. O.|last2=Lovejoy|author-link2=Owen Lovejoy (anthropologist)|year=2014|title=Blood, Bulbs, and Bunodonts: On Evolutionary Ecology and the Diets of ''Ardipithecus'', ''Australopithecus'', and Early ''Homo''|journal=Quarterly Review of Biology|volume=89|issue=4|pages=319–357|pmc=4350785|pmid=25510078|doi=10.1086/678568}}</ref>

The second-to-fourth digit ratios of ''A. ramidus'' are low, consistent with high androgenisation and a disposition towards polygyny.<ref>{{Cite journal |last=Nelson |first=Emma |last2=Rolian |first2=Campbell |last3=Cashmore |first3=Lisa |last4=Shultz |first4=Susanne |date=3 November 2010 |title=Digit ratios predict polygyny in early apes, Ardipithecus , Neanderthals and early modern humans but not in Australopithecus |url=https://royalsocietypublishing.org/doi/10.1098/rspb.2010.1740 |journal=[[Proceedings of the Royal Society B: Biological Sciences]] |language=en |volume=278 |issue=1711 |pages=1556–1563 |doi=10.1098/rspb.2010.1740 |issn=0962-8452 |pmc=3081742 |pmid=21047863 |access-date=10 July 2024}}</ref>

==Paleoecology==
Half of the large mammal species associated with ''A. ramidus'' at Aramis are [[spiral-horned antelope]] and [[colobine monkey]]s (namely ''[[Kuseracolobus]]'' and ''[[Pliopapio]]''). There are a few specimens of primitive [[white rhinoceros|white]] and [[black rhinoceros|black]] rhino species, and elephants, giraffes and hippo specimens are less abundant. These animals indicate that Aramis ranged from wooded grasslands to forests, but ''A. ramidus'' likely preferred the closed habitats,<ref>{{cite journal|first=T. D.|last=White|display-authors=et al.|year=2009|title=Macrovertebrate Paleontology and the Pliocene Habitat of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=67–93|doi=10.1126/science.1175822|pmid=19810193|s2cid=14837552|url=http://doc.rero.ch/record/211327/files/PAL_E4424.pdf}}</ref> specifically riverine areas as such water sources may have supported more canopy coverage.<ref>{{cite journal|first1=M. R.|last1=Gani|first2=N. D.|last2=Gani|year=2011|title=River-margin habitat of ''Ardipithecus ramidus'' at Aramis, Ethiopia 4.4 million years ago|journal=Nature Communications|volume=2|page=602|doi=10.1038/ncomms1610|pmid=22186898|bibcode=2011NatCo...2..602G|doi-access=free}}</ref> Aramis as a whole generally had less than 25% canopy cover.<ref name=Cerling2010>{{cite journal|first1=T. E.|last1=Cerling|author-link1=Thure E. Cerling|first2=N. E.|last2=Levin|first3=J.|last3=Quade|author-link3=Jay Quade|year=2010|title=Comment on the Paleoenvironment of ''Ardipithecus ramidus''|journal=Science|volume=328|issue=5982|page=1105|doi=10.1126/science.1185274|pmid=20508112|bibcode=2010Sci...328.1105C|doi-access=free}}</ref> There were exceedingly high rates of scavenging, indicating a highly competitive environment somewhat like [[Ngorongoro Crater]]. Predators of the area were the hyenas ''[[Ikelohyaena abronia]]'' and ''[[Crocuta dietrichi]]'', the bear ''[[Agriotherium]]'', the cats ''[[Dinofelis]]'' and ''[[Megantereon]]'', the dog ''[[Eucyon]]'', and crocodiles.<ref>{{cite journal|first1=A.|last1=Louchart|first2=H.|last2=Wesselman|first3=R. J.|last3=Blumenschine|display-authors=et al.|year=2009|title=Taphonomic, Avian, and Small-Vertebrate Indicators of ''Ardipithecus ramidus'' Habitat|journal=Science|volume=326|issue=5949|pages=66–66e4|doi=10.1126/science.1175823|pmid=19810192|bibcode=2009Sci...326...66L|s2cid=13825029}}</ref> [[Myrica|Bayberry]], [[Celtis|hackberry]] and [[palm tree|palm]] trees appear to have been common at the time from Aramis to the [[Gulf of Aden]]; and botanical evidence suggests a cool, humid climate.<ref>{{cite journal|first1=G.|last1=WoldeGabriel|author-link1=Giday WoldeGabriel|first2=S. H.|last2=Ambrose|first3=D.|last3=Barboni|display-authors=et al.|year=2009|title=The Geological, Isotopic, Botanical, Invertebrate, and Lower Vertebrate Surroundings of ''Ardipithecus ramidus''|journal=Science|volume=326|issue=5949|pages=65–65e5|doi=10.1126/science.1175817|pmid=19810191|bibcode=2009Sci...326...65W|osti=971297|s2cid=11646395}}</ref> Conversely, annual water deficit (the difference between water loss by [[evapotranspiration]] and water gain by precipitation) at Aramis was calculated to have been about {{cvt|1500|mm}}, which is seen in some of the hottest, driest parts of East Africa.<ref name=Cerling2010/>

[[Carbon isotope]] analyses of the herbivore teeth from the Gona Western Margin associated with ''A. ramidus'' indicate that these herbivores fed mainly on [[C4 plants]] and grasses rather than forest plants. The area seems to have featured [[bushland]] and grasslands.<ref>{{cite book|first1=N. E.|last1=Levin|first2=S. W.|last2=Simpson|first3=J.|last3=Quade|first4=T. E.|last4=Cerling|first5=S. R.|last5=Frost|year=2008|chapter=Herbivore enamel carbon isotopic composition and the environmental context of ''Ardipithecus'' at Gona, Ethiopia|title=The Geology of Early Humans in the Horn of Africa|publisher=Geological Society of America Special Paper|volume=446|pages=215–234|doi=10.1130/2008.2446(10)|isbn=9780813724461}}</ref>

==See also==
{{Div col|colwidth=30em}}
* {{annotated link|Australopithecus|''Australopithecus''}}
* {{annotated link|Ardi}}
* {{annotated link|Graecopithecus|''Graecopithecus''}}
* {{annotated link|Orrorin|''Orrorin''}}
* {{annotated link|Paranthropus|''Paranthropus''}}
* {{annotated link|Sahelanthropus|''Sahelanthropus''}}
{{div col end}}

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

==External links==
{{Wikispecies}}
{{Commons category|Ardipithecus ramidus}}

* [http://gurche.com/ardipithecus-ramidus Reconstruction] by [[John Gurche]]
* [http://humanorigins.si.edu/evidence/human-fossils/species/ardipithecus-ramidus The Smithsonian Institution's Human Origins Program]
* [https://web.archive.org/web/20130318211338/http://dsc.discovery.com/tv-shows/other-shows/videos/other-shows-discovering-ardi-videos.htm 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).

{{Human Evolution}}
{{Breakthrough of the Year}}
{{Taxonbar|from=Q312222}}

[[Category:Australopithecus fossils]]
[[Category:Fossil taxa described in 1994]]
[[Category:Miocene species first appearances]]
[[Category:Pliocene primates]]
[[Category:Prehistoric Ethiopia]]
[[Category:Transitional fossils]]
[[Category:Zanclean extinctions]]