View source for Biology:Australopithecus anamensis

{{short description|Extinct hominin from Pliocene east Africa}}
{{Speciesbox
| image = Australopithecus afarensis Cleveland Museum.jpg <!-- image filename mistakenly labels the skull as afarensis -->
| image_caption = Reconstructed skull at the Cleveland Museum of Natural History
| fossil_range = {{fossil range|Pliocene}}
| extinct = yes
| genus = Australopithecus
| species = anamensis
| authority = M.G. Leakey et al., 1995
| synonyms = *{{extinct}}''[[Biology:Praeanthropus|Praeanthropus]] anamensis'' <small></small>
| synonyms_ref = 
| subdivision_ranks = 
| subdivision = 
}}

'''''Australopithecus anamensis''''' is a hominin [[Biology:Species|species]] that lived approximately between 4.2 and 3.8 million years ago<ref>RFI Afrique par Simon Rozé Publié le 28-08-2019 Modifié le 29-08-2019 à 11:00, http://www.rfi.fr/afrique/20190828-ethiopie-decouverte-plus-vieux-fossile-australopitheque</ref> and is the oldest known ''[[Biology:Australopithecus|Australopithecus]]'' species,<ref name="Haile-Selassie2010c">{{cite journal |author=Haile-Selassie, Y |date=27 October 2010 |title=Phylogeny of early Australopithecus: new fossil evidence from the Woranso-Mille (central Afar, Ethiopia)|journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=365 |issue=1556 |pages=3323–3331 |pmid=20855306 |pmc=2981958 |doi=10.1098/rstb.2010.0064}}</ref> living during the [[Earth:Plio-Pleistocene|Plio-Pleistocene]] era.<ref name=":12">{{Cite book|title=Understanding Humans: Introduction to Physical Anthropology and Archaeology|last=Lewis|first=Barry |display-authors=0 |year=2013|edition=11th|location=Belmont, CA: Wadsworth Publishing}}</ref>

Nearly one hundred [[Biology:Fossil|fossil]] specimens of ''A. anamensis'' are known from Kenya<ref name="M. G. Leakey, C. S. Feibel, I. MacDougall & A. Walker 565–571">{{cite journal |first1=Meave G. |last1=Leakey |first2=Craig S. |last2=Feibel |first3=Ian |last3=MacDougall |first4=Alan |last4=Walker |author4-link=Alan Walker (anthropologist) |date=17 August 1995 |title=New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya |journal=Nature |pmid=7637803 |volume=376 |issue=6541 |pages=565–571 |doi=10.1038/376565a0 |bibcode=1995Natur.376..565L|s2cid=4340999 }}</ref><ref name="Leakey et al., 1998">{{cite journal |first1=Meave G. |last1=Leakey |author-link=Meave G. Leakey |first2=Craig S. |last2=Feibel |first3=Ian |last3=MacDougall |author3-link=Ian McDougall (geologist) |last4=Ward |first4=Carol |first5=Alan |last5=Walker |author5-link=Alan Walker (anthropologist) |date=7 May 1998 |title=New specimens and confirmation of an early age for ''Australopithecus anamensis'' |journal=Nature |pmid=9590689 |volume=393 |issue=6680 |pages=62–66 |doi=10.1038/29972 |bibcode=1998Natur.393...62L|s2cid=4398072 }}</ref> and Ethiopia,<ref name="WhiteEtal2006nature04629">{{cite journal |first1=Tim D. |last1=White |first2=Giday |last2=WoldeGabriel |first3=Berhane |last3=Asfaw |first4=Stan |last4=Ambrose |first5=Yonas |last5=Beyene |first6=Raymond L. |last6=Bernor |first7=Jean-Renaud |last7=Boisserie |first8=Brian |last8=Currie |first9=Henry |last9=Gilbert |first10=Yohannes |last10=Haile-Selassie |first11=William K. |last11=Hart |first12=Leslea J. |last12=Hlusko |first13=F. Clark |last13=Howell |first14=Reiko T. |last14=Kono |first15=Thomas |last15=Lehmann |first16=Antoine |last16=Louchart |first17=C. Owen |last17=Lovejoy |first18=Paul R. |last18=Renne |first19=Hauro |last19=Saegusa |first20=Elisabeth S. |last20=Vrba |first21=Hank |last21=Wesselman |first22=Gen |last22=Suwa |date=13 April 2006 |title=Asa Issie, Aramis and the origin of ''Australopithecus'' |journal=Nature |pmid=16612373 |volume=440 |issue=7086 |pages=883–9 |doi=10.1038/nature04629 |bibcode=2006Natur.440..883W|s2cid=4373806 }}</ref> representing over twenty individuals. The first fossils of ''A. anamensis'' discovered, are dated to around 3.8 and 4.2 million years ago and were found in Kanapoi and Allia Bay in Northern Kenya.<ref name=":023">{{Cite journal|last1=Ward|first1=Carol|last2=Leakey|first2=Meave|last3=Walker|first3=Alan|date=1999|title=The new hominid species Australopithecus anamensis|journal=Evolutionary Anthropology: Issues, News, and Reviews|language=en|volume=7|issue=6|pages=197–205|doi=10.1002/(SICI)1520-6505(1999)7:6<197::AID-EVAN4>3.0.CO;2-T|s2cid=84278748 |issn=1520-6505}}</ref>

It is usually accepted that ''[[Biology:Australopithecus afarensis|A. afarensis]]'' emerged within this lineage.<ref name="Kimbel">{{cite journal |last1=Kimbel |first1=William H. |last2=Lockwood |first2=Charles A. |first3=Carol V. |last3=Ward |first4=Meave G. |last4=Leakey |author4-link=Meave G. Leakey |first5=Yoel |last5=Rake |first6=Donald C. |last6=Johanson |title=Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record |journal=Journal of Human Evolution |year=2006 |volume=51 |issue=2 |pages=134–152 |doi=10.1016/j.jhevol.2006.02.003 |pmid=16630646}}</ref> However,  ''A. anamensis'' and ''A. afarensis'' appear to have lived side by side for at least some period of time, and it is not fully settled whether the lineage that led to extant humans emerged in ''A. afarensis'', or directly in ''A. anamensis.''<ref name=Nature573pp214-219>{{cite journal|last1=Haile-Selassie|first1=Yohannes|last2=Melillo|first2=Stephanie M.|last3=Vazzana|first3=Antonino|last4=Benazzi|first4=Stefano|last5=Ryan|first5=Timothy M.|title=A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia|journal=Nature|volume=573|issue=7773|pages=214–219|year=2019|doi=10.1038/s41586-019-1513-8|pmid=31462770|bibcode=2019Natur.573..214H|hdl=11585/697577|s2cid=201656331|hdl-access=free}}</ref><ref name="Price">{{Cite web|url=https://www.science.org/content/article/stunning-ancient-skull-shakes-human-family-tree|title=Stunning ancient skull shakes up human family tree|last1=Price|first1=Michael|date=2019-08-28|website=Science {{!}} AAAS|language=en|access-date=2019-10-29}}</ref><ref>{{Cite news|url=https://www.irishtimes.com/news/science/skull-discovery-a-game-changer-in-understanding-of-human-evolution-1.4001736|title=Skull discovery 'a game changer' in understanding of human evolution|newspaper=The Irish Times|language=en|access-date=2019-10-29}}</ref>
Fossil evidence determines that ''Australopithecus anamensis'' is the earliest hominin species in the [[Biology:Turkana Basin|Turkana Basin]],<ref name="pnas.org">{{cite journal |last1=Cerling |first1=Thure E. |first2=Fredrick Kyalo |last2=Manthi |first3=Emma N. |last3=Mbua |first4=Louise N. |last4=Leakey |author4-link=Louise N. Leakey |first5=Meave G. |last5=Leakey |author5-link=Meave G. Leakey |first6=Richard E. |last6=Leakey |author6-link=Richard E. Leakey |first7=Francis H. |last7=Brown |first8=Frederick E. |last8=Grine |first9=John A. |last9=Hart |first10=Prince |last10=Kalemeg |first11=Hélène |last11=Roche |first12=Kevin T. |last12=Uno |first13=Bernard A. |last13=Wood |title=Stable isotope-based diet reconstructions of Turkana Basin hominins |journal=Proceedings of the National Academy of Sciences of the United States of America |date=June 25, 2013 |volume=110 |issue=26 |pages=10501–10506 |doi=10.1073/pnas.1222568110 |bibcode = 2013PNAS..11010501C |pmid=23733966 |pmc=3696807|doi-access=free }}</ref> but likely co-existed with ''afarensis'' towards the end of its existence.<ref name=Nature573pp214-219/><ref name="TC-20190904">{{cite web |last=Hanegraef |first=Hester |title=How the skull of humanity's oldest known ancestor is changing our understanding of evolution |url=https://theconversation.com/how-the-skull-of-humanitys-oldest-known-ancestor-is-changing-our-understanding-of-evolution-122926 |date=4 September 2019 |work=The Conversation |access-date=8 September 2019 }}</ref> ''A. anamensis'' and ''A. afarensis'' may be treated as a single grouping.<ref>{{Cite journal|last1=Du|first1=Andrew|last2=Rowan|first2=John|last3=Wang|first3=Steve C.|last4=Wood|first4=Bernard A.|last5=Alemseged|first5=Zeresenay|date=2020-01-01|title=Statistical estimates of hominin origination and extinction dates: A case study examining the Australopithecus anamensis–afarensis lineage|journal=Journal of Human Evolution|volume=138|pages=102688|doi=10.1016/j.jhevol.2019.102688|pmid=31759257|issn=0047-2484|doi-access=free}}</ref>

Preliminary analysis of the sole upper [[Biology:Skull|cranial]] fossil indicates ''A. anamensis'' had a smaller cranial capacity (estimated 365-370 [[Biology:Brain size#Cranial capacity|c.c.]]) than ''A. afarensis''.<ref name=Nature573pp214-219/>
{{Human timeline}}
== Discovery ==
[[File:Australopithecus anamensis bone (University of Zurich).JPG|thumb|left|''A. anamensis'' bone at the University of Zürich]]
The first fossilized specimen of the species, although not recognized as such at the time, was a single fragment of [[Biology:Humerus|humerus]] (arm bone) found in Pliocene strata in the Kanapoi region of West Lake Turkana by a [[Organization:Harvard University|Harvard University]] research team in 1965.<ref name="The new hominid species"/> Bryan Patterson and William W. Howells's initial paper on the bone was published in ''Science'' in 1967; their initial analysis suggested an ''Australopithecus'' specimen and an age of 2.5 million years.<ref>{{cite journal|last1=Patterson|first1=B.|last2=Howells|first2=W. W.|title=Hominid Humeral Fragment from Early Pleistocene of Northwestern Kenya|journal=Science|date=1967|volume=156|issue=3771|pages=64–66|doi=10.1126/science.156.3771.64|pmid=6020039|bibcode=1967Sci...156...64P|s2cid=19423095}}</ref> Patterson and colleagues subsequently revised their estimation of the specimen's age to 4.0–4.5 mya based on faunal correlation data.<ref>{{cite journal|last1=Patterson|first1=B|last2=Behrensmeyer|first2=AK|last3=Sill|first3=WD|title=Geology and Fauna of a New Pliocene Locality in North-western Kenya|journal=Nature|date=1970|volume=226|issue=5249|pages=918–921|doi=10.1038/226918a0|pmid=16057594|bibcode=1970Natur.226..918P|s2cid=4185736}}</ref><ref name="The new hominid species">{{cite journal|last1=Ward|first1=C|last2=Leaky|first2=M|last3=Walker|first3=A|title=The new hominid species ''Australopithecus anamensis''|journal=Evolutionary Anthropology|date=1999|volume=7|issue=6|pages=197–205|doi=10.1002/(sici)1520-6505(1999)7:6<197::aid-evan4>3.0.co;2-t|s2cid=84278748}}</ref>

In 1994, the London-born Kenyan [[Biology:Paleoanthropology|paleoanthropologist]] Meave Leakey and archaeologist Alan Walker excavated the Allia Bay site and uncovered several additional fragments of the hominid, including one complete lower jaw bone which closely resembles that of a [[Biology:Common chimpanzee|common chimpanzee]] ''(Pan troglodytes)'' but whose teeth bear a greater resemblance to those of a [[Biology:Human|human]]. Based on the limited postcranial evidence available, ''A. anamensis'' appears to have been habitually bipedal, although it retained some primitive features of its upper limbs.<ref>{{cite journal|last1=C.V.|first1=Warda|s2cid=41320275|title=Morphology of ''Australopithecus anamensis'' from Kanapoi and Allia Bay, Kenya|doi=10.1006/jhev.2001.0507|pmid=11599925|volume=41|issue=4|journal=Journal of Human Evolution|pages=255–368|year=2001}}</ref>

In 1995, Meave Leakey and her associates, taking note of differences between ''[[Biology:Australopithecus afarensis|Australopithecus afarensis]]'' and the new finds, assigned them to a new species, ''A. anamensis'', deriving its name from the [[Social:Turkana language|Turkana]] word ''anam'', meaning "lake".<ref name="M. G. Leakey, C. S. Feibel, I. MacDougall & A. Walker 565–571"/>
Although the excavation team did not find hips, feet or legs, Meave Leakey believes that ''Australopithecus anamensis'' often climbed trees. [[Biology:Tree climbing|Tree climbing]] was one behavior retained by early hominins until the appearance of the first ''[[Biology:Homo|Homo]]'' species about 2.5 million years ago. ''A. anamensis'' shares many traits with ''Australopithecus afarensis'' and may well be its direct predecessor. Fossil records for ''A. anamensis'' have been dated to between 4.2 and 3.9 million years ago,<ref name=McHenry2009>{{Cite book|year=2009|last=McHenry|first=Henry M|chapter=Human Evolution|pages=[https://archive.org/details/evolutionfirstfo00mich/page/256 256–280]|editor1=Michael Ruse|editor2=Joseph Travis|title=Evolution: The First Four Billion Years|publisher=Harvard University Press |isbn=978-0-674-03175-3|chapter-url-access=registration|chapter-url=https://archive.org/details/evolutionfirstfo00mich|url=https://archive.org/details/evolutionfirstfo00mich/page/256}} (see pp.263-265)</ref> with findings in the 2000s from stratigraphic sequences dating to about 4.1–4.2 million years ago.<ref name="WhiteEtal2006nature04629"/> Specimens have been found between two layers of [[Earth:Volcanic ash|volcanic ash]], dated to 4.17 and 4.12 million years, coincidentally when ''A. afarensis'' appears in the fossil record.<ref name="Leakey et al., 1998" />

The fossils (twenty one in total) include [[Biology:Maxilla|upper and]] lower jaws, cranial fragments, and the upper and lower parts of a leg bone ([[Biology:Tibia|tibia]]). In addition to this, the aforementioned fragment of [[Biology:Humerus|humerus]] found in 1965 at the same site at Kanapoi has now been assigned to this species.

[[File:Australopithecus anamensis 5476.JPG|thumb|left|''A. anamensis'' jaws and limbs]]
In 2006, a new ''A. anamensis'' find was officially announced, extending the range of ''A. anamensis'' into northeast Ethiopia. Specifically, one site known as Asa Issie provided 30 ''A. anamensis'' fossils.<ref name="Ward, Manthi">{{cite journal|last1=Ward|first1=Carol|last2=Manthi|first2=Frederick|title=New Fossils of Australopithecus Anamensis from Kanapoi, Kenya and Evolution Within the A. Anamensis-Afarensis Lineage|journal=Journal of Vertebrate Paleontology|date=September 2008|volume=28|issue=Sup 003|page=157A|doi=10.1080/02724634.2008.10010459|s2cid=220405736 }}</ref> These new fossils, sampled from a woodland context, include the largest hominid [[Biology:Canine tooth|canine tooth]] yet recovered and the earliest ''Australopithecus'' [[Biology:Femur|femur]].<ref name="WhiteEtal2006nature04629"/> The find was in an area known as [[History:Middle Awash|Middle Awash]], home to several other more modern ''Australopithecus'' finds and only six miles (9.7 kilometers) away from the discovery site of ''[[Biology:Ardipithecus ramidus|Ardipithecus ramidus]]'', the most modern species of ''[[Biology:Ardipithecus|Ardipithecus]]'' yet discovered. ''Ardipithecus'' was a more primitive hominid, considered the next known step below ''Australopithecus'' on the evolutionary tree. The ''A. anamensis'' find is dated to about 4.2 million years ago, the ''Ar. ramidus'' find to 4.4 million years ago, placing only 200,000 years between the two species and filling in yet another blank in the pre-''Australopithecus'' hominid evolutionary timeline.<ref name="New fossil links up human evolution">{{cite journal| first=Seth|last=Borenstein| journal=USA Today|title=New fossil links up human evolution}}</ref>

In 2010 journal articles were published by Yohannes Haile-Selassie and others describing the discovery of around 90 fossil specimens in the time period 3.6 to 3.8 million years ago (mya), in the Afar area of Ethiopia, filling in the time gap between ''A. anamensis'' and ''[[Biology:Australopithecus afarensis|Australopithecus afarensis]]'' and showing a number of features of both. This supported the idea (proposed for instance by Kimbel et al. in 2006<ref name="Kimbel"/>) that ''A. anamensis'' and ''A. afarensis'' were in fact one evolving species (i.e. a [[Biology:Chronospecies|chronospecies]] resulting from [[Biology:Anagenesis|anagenesis]]),<ref name="Haile-Selassie2010c"/> but in August 2019, scientists from the same Haile-Selassie team announced the discovery of a nearly intact skull for the first time, and dated to 3.8 mya, of ''A. anamensis'' in Ethiopia. This discovery also indicated that an earlier forehead bone fossil from 3.9 mya was ''A. afarensis'' and therefore the two species over-lapped and could not be a chronospecies (noting that this does not prevent A. afarensis being descended from ''A. anamensis'', but would be descended from only part of the ''A. anamensis'' population).<ref name=Nature573pp214-219/><ref name="GZM-20190828">{{cite news |last=Dvorsky |first=George |title=Incredible Fossil Discovery Finally Puts a Face on an Elusive Early Hominin |url=https://gizmodo.com/incredible-fossil-discovery-finally-puts-a-face-on-an-e-1837657550 |date=28 August 2019 |work=Gizmodo |access-date=28 August 2019 }}</ref> The skull itself was found by Afar herder Ali Bereino in 2016.<ref name="nationalgeographic.com">Greshko, Michael, ''[https://web.archive.org/web/20190828220516/https://www.nationalgeographic.com/science/2019/08/unprecedented-fossil-skull-reveals-face-of-human-ancestor/ 'Unprecedented' skull reveals face of human ancestor]'', National Geographic, August 28, 2019</ref> Other scientists (e.g. Alemseged, Kimbel, Ward, White) cautioned that one forehead bone fossil, which they viewed as not conclusively ''A. afarensis'', should not be taken as disproving the possibility of anagenesis yet.<ref name="Price"/><ref name="GZM-20190828"/>

In August 2019, scientists announced the discovery of MRD-VP-1/1, a nearly intact skull, for the first time, and dated to 3.8 million years ago, of ''A. anamensis'' in Ethiopia.<ref name=":0">{{cite journal|last1=Haile-Selassie|first1=Yohannes|last2=Melillo|first2=Stephanie M.|last3=Vazzana|first3=Antonino|last4=Benazzi|first4=Stefano|last5=Timothy|first5=M. Ryan|year=2019|title=A 3.8-million-year-old hominin cranium from Woranso-Mille, Ethiopia|journal=Nature|volume=573|issue=7773|pages=214–219|doi=10.1038/s41586-019-1513-8|bibcode=2019Natur.573..214H|pmid=31462770|hdl=11585/697577|s2cid=201656331|hdl-access=free}}</ref><ref name="GZM-201908282">{{cite news|url=https://gizmodo.com/incredible-fossil-discovery-finally-puts-a-face-on-an-e-1837657550|title=Incredible Fossil Discovery Finally Puts a Face on an Elusive Early Hominin|last=Dvorsky|first=George|date=28 August 2019|work=Gizmodo|access-date=28 August 2019}}</ref> The skull itself was found by Afar herder Ali Bereino in 2016.<ref name="nationalgeographic.com"/>  This skull is important in supplementing the evolutionary lineage of [[Biology:Hominini|hominins]].  The skull has a unique combination of derived and ancestral characteristics.<ref name=":0" />  It was determined that the cranium is older than ''[[Biology:Australopithecus afarensis|A. afarensis]]'' through analyzing that the cranial capacity is much smaller and the face is very [[Medicine:Prognathism|prognathic]], both of which indicate that it is earlier than ''[[Biology:Australopithecus afarensis|A. afarensis]]''.<ref name=":0" />  Known as the MRD cranium, it is that of a male who was at an "advanced developmental age" determined by the worn down post-canine teeth.<ref name=":0" />  The teeth show mesiodistal elongation, which differs from ''[[Biology:Australopithecus afarensis|A. afarensis]].''<ref name=":0" />  Similar to other [[Biology:Australopithecus|australopiths]], however, it has a narrow upper face with no forehead and a large mid-face with broad [[Biology:Zygomatic bone|zygomatic]] bones.<ref name=":0" />  Before this new discovery, it was widely believed that ''Australopithecus anamensis'' and ''[[Biology:Australopithecus afarensis|Australopithecus afarensis]]'' evolved one right after the other in a single lineage.<ref name=":0" />  However, with the discovery of MRD, it suggests that ''[[Biology:Australopithecus afarensis|A. afarensis]]'' did not result from [[Biology:Anagenesis|anagenesis]], but that the two hominin species lived side by side for at least 100,000 years.<ref name=":0" /><ref>{{Cite web|url=https://www.cnn.com/2019/08/28/world/early-human-skull-discovery-australopithecus-anamensis-scn/index.html|title=Revealing the new face of a 3.8-million-year-old early human ancestor|website=CNN|date=28 August 2019}}</ref>

==Environment==
''Australopithecus anamensis'' was found in Kenya, specifically at Allia Bay, East Turkana. Through analysis of stable isotope data, it is believed that their environment had more closed woodland canopies surrounding Lake Turkana than are present today. The greatest density of woodlands at Allia Bay was along the ancestral Omo River. There was believed to be more open savanna in the basin margins or uplands. Similarly at Allia Bay, it is suggested that the environment was much wetter. While it is not definitive, it also could have been possible that nut or seed-bearing trees could have been present at Allia Bay, however more research is needed.<ref>{{cite journal |last1=Schoeninger |first1=Margaret|last2=Reeser |first2=Holly |last3=Hallin |first3=Kris |title=Paleoenvironment of ''Australopithecus anamensis'' at Allia Bay, East Turkana, Kenya: evidence from mammalian herbivore enamel stable isotopes |journal=Journal of Anthropological Archaeology |date=September 2003 |volume=22 |issue=3 |pages=200–207 |doi=10.1016/s0278-4165(03)00034-5}}</ref>

==Diet==
Studies of the microwear on ''Australopithecus anamensis'' molar fossils show a pattern of long striations. This pattern is similar to the microwear on the molars of gorillas; suggesting that ''Australopithecus anamensis'' had a similar diet to that of the modern gorilla.<ref>{{cite journal |first1=Peter S. |last1=Ungar |first2=Robert S. |last2=Scott |first3=Frederick E. |last3=Grine |first4=Mark F. |last4=Teaford |title=Molar microwear textures and the diets of ''Australopithecus anamensis'' and ''Australopithecus afarensis'' |date=20 September 2010 |doi=10.1098/rstb.2010.0033 |pmid=20855308 |volume=365 |issue=1556 |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |pages=3345–3354|pmc=2981952 }}</ref>
The microwear patterns are consistent on all ''Australopithecus anamensis'' molar fossils regardless of location or time. This shows that their diet largely remained the same no matter what their environment.

The earliest dietary isotope evidence in Turkana Basin hominin species comes from the ''Australopithecus anamensis''. This evidence suggests that their diet consisted primarily of C3 resources, possibly however with a small amount of C4 derived resources. Within the next 1.99- to 1.67-Ma time period, at least two distinctive hominin taxa shifted to a higher level of C4 resource consumption. At this point, there is no known cause for this shift in diet. One should recognize that this research does not by itself indicate a plant-based diet, because the isotopes can be ingested by eating animals and insects that fed on C3 and C4 resources.<ref name="pnas.org"/>

''A. anamensis'' had thick, long, and narrow jaws with their side teeth arranged in parallel lines.<ref name=":22">{{Cite web|url=http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-anamensis|title=Australopithecus anamensis|date=2010-02-11|website=The Smithsonian Institution's Human Origins Program|language=en|access-date=2019-11-10}}</ref>  The palate, rows of teeth, and other characteristics of A. ''anamensis'' dentition suggests that they were omnivores and their diets were composed heavily on fruit, similar to [[Biology:Chimpanzee|chimpanzee]]s.<ref name=":023"/> These characteristics came from ''Ar. ramidus'', who were thought to have preceded ''A. anamensis''.  Evidence of a dietary shift was also found, suggesting the consumption of harder foods.<ref name=":023"/> This was indicated by thicker enamel in teeth and more intense molar crowns.<ref name=":023"/>

== Relation to other hominin species ==
''Australopithecus anamensis'' is the intermediate species between ''Ardipithecus ramidus'' and ''Australopithecus afarensis'' and has multiple shared traits with humans and other apes.<ref name=":22"/><ref name=":023"/> Fossil studies of the wrist morphology of ''A. anamensis'' have suggested knuckle-walking, which is a derived trait shared with other African apes. The ''A. anamensis'' hand portrays robust phalanges and metacarpals, and long middle phalanges. These characteristics show that the ''A. anamensis'' likely engaged in arboreal living but were largely bipedal, although not in an identical way to ''[[Biology:Homo|Homo]]''.<ref>{{Cite journal|url=https://www.nature.com/articles/35006045|title=Evidence that Humans Evolved from a Knuckle-walking Ancestor|last=Richmond|first=Brian|date=23 March 2000|journal=Nature|volume=404|issue=6776|pages=382–385|doi=10.1038/35006045|pmid=10746723|bibcode=2000Natur.404..382R|s2cid=4303978}}</ref>

All ''Australopithecus'' were bipedal, small-brained, and had large teeth.<ref name=":12"/> ''A. anamensis'' is often confused with ''Australopithecus afarensis'' due to their similar bone structure and their habitation of woodland areas.<ref>{{Cite web|url=https://www.britannica.com/topic/Australopithecus|title=Australopithecus - Australopithecus afarensis and Au. garhi|website=Encyclopedia Britannica|language=en|access-date=2019-11-10}}</ref>  These similarities include thick tooth enamel, which is a shared derived trait of all ''Australopithecus'' and shared with most Miocene hominoids.<ref name=":023" />  Tooth size variability in ''A. anamensis'' suggests that there was significant body size variation.<ref name=":023" />  In relation to their diet, ''A. anamensis'' has similarities with their predecessor ''[[Biology:Ardipithecus ramidus|Ardipithecus ramidus]]''.<ref name=":023" />  ''A. anamensis'' sometimes had much larger canines than later ''Australopithecus'' species.<ref name=":023" /> ''A. anamensis'' and ''A. afarensis'' have similarities in the [[Biology:Humerus|humerus]] and the [[Biology:Tibia|tibia]].<ref name=":023" /> They both have human-like features and matching sizes.<ref name=":023" /> It has also been found that the bodies of ''A. anamensis'' are somewhat larger than those of ''A. afarensis''.<ref name=":023" /> Based on additional ''afarensis'' collections from the Hadar, Ethiopia site, the ''A. anamensis'' radius is similar to that of ''afarensis'' in the lunate and [[Biology:Scaphoid bone|scaphoid]] surfaces.<ref name=":023" /> Additional findings suggest that ''A. anamensis'' have long arms compared to modern humans.<ref name=":023" />

== Physical characteristics ==
Based on fossil evidence, ''A. anamensis'' expresses high degrees of [[Biology:Sexual dimorphism|sexual dimorphism]].<ref name=":02">{{Cite journal |last=Welker |first=Barbara Helm |date=2017-06-13 |title=10. Australopithecus anamensis |url=https://milnepublishing.geneseo.edu/the-history-of-our-tribe-hominini/chapter/australopithecus-anamensis/ |language=en}}</ref> Although considered to be the more primitive of the australopiths, ''A. anamensis'' had parts of the knee, tibia, and elbow that were different from apes, which indicates bipedalism as the species' form of locomotion.<ref name=":02" /> Specifically, the tibia bone of ''A. anamensis'' has a more expansive upper end with bone.<ref name=":13">{{Cite web |title=Australopithecus anamensis |url=http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-anamensis |access-date=2022-02-11 |website=The Smithsonian Institution's Human Origins Program |language=en}}</ref>

In addition to the modified body parts that indicate bipedalism, ''A. anamensis'' fossils show evidence of tree climbing. Archeology finds indicate that ''A. anamensis'' had long forearms, as well as modified features of the wrist bone.<ref name=":13"/> Both the forearms and finger bones of ''A. anamensis'' indicate a potential of utilizing the upper limbs as support when operating in trees or on the ground.<ref name=":23">{{Cite book |last=Sawyer |first=G.J. |title=The Last Human: A Guide to Twenty-Two Species of Extinct Humans |publisher=Yale University Press |year=2007 |isbn=978-0-300-10047-1 |pages=51}}</ref> Forearm bones belonging to ''A. anamensis'' have been found to be 265 millimeters to 277 millimeters in length.<ref name=":23" /> The curved proximal hand phalanx of A. anamensis in the fossil record that contains strong ridges is indicative of its potential ability to climb.<ref>{{Cite journal |last1=McHenry |first1=Henry M. |last2=Coffing |first2=Katherine |date=2000-10-21 |title=Australopithecus to Homo: Transformations in Body and Mind |url=https://www.annualreviews.org/doi/10.1146/annurev.anthro.29.1.125 |journal=Annual Review of Anthropology |volume=29 |issue=1 |pages=125–146 |doi=10.1146/annurev.anthro.29.1.125 |issn=0084-6570}}</ref>

Fossil evidence reveals that ''A. anamensis'' had a somewhat wide jaw joint that was flat from front to back, which resembles a curvature similar to those seen in great apes.<ref name=":34">{{Cite book |last=Sawyer |first=G.J. |title=The Last Human: A Guide to Twenty-Two Species of Extinct Humans |publisher=Yale University Press |year=2007 |isbn=978-0-300-10047-1 |pages=50}}</ref> Furthermore, the ear canal of A. anamensis fossils are narrow in diameter. The ear canal most resembles that of chimpanzees and is contrasting to the wide ear canals of both later ''Australopithecus'' and ''Homo.''<ref name=":34" />

The first lower premolar of ''A. anamensis'' is characterized by a singular large cusp. Additionally, ''A. anamensis'' has a narrow first milk molar that contains a large dominant cusp with minimum surface area, which may have been used for crushing.<ref name=":34" />

== See also ==
* [[Biology:List of human evolution fossils|List of human evolution fossils]]

==References==
{{Reflist|2}}

==External links==
* [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – Smithsonian, National Museum of Natural History (August 2016).
{{Human Evolution}}
{{Taxonbar|from=Q310520}}

{{DEFAULTSORT:Australopithecus Anamensis}}
[[Category:Australopithecus]]
[[Category:Pliocene primates]]

{{Sourceattribution|Australopithecus anamensis}}