Editing Australopithecus afarensis

{{Short description|Extinct hominid from the Pliocene of East Africa}}
{{Good article}}
{{Speciesbox
| fossil_range = {{nowrap|[[Zanclean]] – [[Piacenzian]]}}<br />{{Fossil range|3.9|2.9}}
| image = Reconstruction of the fossil skeleton of "Lucy" the Australopithecus afarensis.jpg
| image_caption = The partial skeleton AL 288-1 ("[[Lucy (Australopithecus)|Lucy]]")
| genus = Australopithecus
| species = afarensis
| authority = [[Donald Johanson|Johanson]], [[Timothy White (anthropologist)|White]], and [[Yves Coppens|Coppens]], 1978<ref name=Johanson1978>{{cite journal|last1=Johanson|first1=Donald C.|author-link=Donald Johanson|last2=White|first2=Tim D.|author-link2=Timothy White (anthropologist)|last3=Coppens|first3=Yves|author-link3=Yves Coppens|title=A New Species of the Genus ''Australopithecus'' (Primates: Hominidae) from the Pliocene of Eastern Africa|journal=Kirtlandia|date=1978|volume=28|pages=1–14|url=https://www.biodiversitylibrary.org/page/51811016}}</ref>
| synonyms = {{collapsible list|title=Synonyms|
* ''Praeanthropus africanus''<br /><small>(Weinert, 1950)</small>
* ''Australopithecus aethiopicus''<br /><small>Tobias, 1980</small>
* ''Homo aethiopicus''<br /><small>(Tobias, 1980)</small>
* ''Homo antiquus''<br /><small>[[Walter Ferguson|Ferguson]], 1984</small>
* ''Afaranthropus antiquus''<br /><small>([[Walter Ferguson|Ferguson]], 1984)</small>
* ''Homo hadar''<br /><small>Bonde and Westergaard, 2004</small>
* ''[[A. bahrelghazali]]''?<br /><small>[[Michel Brunet (paleontologist)|Brunet]] et al., 1996</small>
* ''[[A. deyiremeda]]''?<br /><small>[[Yohannes Haile-Selassie|Haile-Selassie]] et al., 2015</small>
}}
}}
'''''Australopithecus afarensis''''' is an [[extinct]] [[species]] of [[australopithecine]] which lived from about 3.9–2.9 million years ago (mya) in the [[Pliocene]] of [[East Africa]]. The first [[fossil]]s were discovered in the 1930s, but major fossil finds would not take place until the 1970s. From 1972 to 1977, the International Afar Research Expedition—led by anthropologists [[Maurice Taieb]], [[Donald Johanson]] and [[Yves Coppens]]—unearthed several hundreds of [[hominin]] specimens in [[Hadar, Ethiopia|Hadar]], [[Ethiopia]], the most significant being the exceedingly well-preserved skeleton AL 288-1 ("[[Lucy (Australopithecus)|Lucy]]") and the site [[AL 333]] ("the First Family"). Beginning in 1974, [[Mary Leakey]] led an expedition into [[Laetoli]], [[Tanzania]], and notably recovered [[fossil trackway]]s. In 1978, the species was first [[species description|described]], but this was followed by arguments for splitting the wealth of specimens into different species given the wide range of variation which had been attributed to [[sexual dimorphism]] (normal differences between males and females). ''A. afarensis'' probably descended from ''[[A. anamensis]]'' and is hypothesised to have given rise to ''[[Homo]]'', though the latter is debated.

''A. afarensis'' had a tall face, a delicate brow ridge, and [[prognathism]] (the jaw jutted outwards). The jawbone was quite robust, similar to that of [[gorilla]]s. The living size of ''A. afarensis'' is debated, with arguments for and against marked size differences between males and females. Lucy measured perhaps {{cvt|105|cm|ftin}} in height and {{cvt|25–37|kg}}, but she was rather small for her species. In contrast, a presumed male was estimated at {{cvt|165|cm|ftin}} and {{cvt|45|kg}}. A perceived difference in male and female size may simply be [[sampling bias]]. The leg bones as well as the Laetoli fossil trackways suggest ''A. afarensis'' was a competent [[biped]], though somewhat less efficient at walking and slower at running than humans. The arm and shoulder bones have some similar aspects to those of [[orangutan]]s and gorillas, which has variously been interpreted as either evidence of partial tree-dwelling ([[arboreal]]ity), or [[basal (phylogenetics)|basal]] traits inherited from the [[chimpanzee–human last common ancestor]] with no adaptive functionality.

''A. afarensis'' was probably a [[generalist and specialist species|generalist]] [[omnivore]] of both [[C3 carbon fixation|C<sub>3</sub>]] forest plants and [[C4 carbon fixation|C<sub>4</sub>]] [[Crassulacean acid metabolism|CAM]] savanna plants—and perhaps creatures which ate such plants—and was able to exploit a variety of different food sources. Similarly, ''A. afarensis'' appears to have inhabited a wide range of habitats with no real preference, inhabiting open grasslands or woodlands, shrublands, and lake- or riverside forests. Potential evidence of [[stone tool]] use would indicate meat was also a dietary component. Marked sexual dimorphism in primates typically corresponds to a [[Polygyny in animals|polygynous]] society and low dimorphism to [[Monogamy in animals|monogamy]], but the group dynamics of early hominins is difficult to predict with accuracy. Early hominins may have fallen prey to the large carnivores of the time, such as [[big cat]]s and [[hyena]]s.

==Taxonomy==
===Research history===
Beginning in the 1930s, some of the most ancient [[hominin]] remains of the time dating to 3.8–2.9 million years ago were recovered from East Africa. Because ''[[Australopithecus africanus]]'' fossils were commonly being discovered throughout the 1920s and '40s in South Africa, these remains were often provisionally classified as ''Australopithecus'' [[species affinis|aff.]] ''africanus''.<ref name=Johanson1978/> The first to identify a human fossil was German explorer [[Ludwig Kohl-Larsen]] in 1939 by the headwaters of the Gerusi River (near [[Laetoli]], Tanzania), who encountered a [[maxilla]].<ref>{{cite book|first=V.|last=Morell|year=2011|title=Ancestral Passions: The Leakey Family and the Quest for Humankind's Beginnings|publisher=Simon and Schuster|page=445|isbn=978-1-4391-4387-2}}</ref> In 1948, German palaeontologist [[Edwin Hennig]] proposed classifying it into a new [[genus]], "''Praeanthropus''", but he failed to give a species name. In 1950, German anthropologist [[Hans Weinert]] proposed classifying it as ''Meganthropus africanus'', but this was largely ignored. In 1955, M.S. Şenyürek proposed the combination ''Praeanthropus africanus''.<ref name=Johanson1978/> Major collections were made in [[Laetoli]], Tanzania, on an expedition beginning in 1974 directed by British palaeoanthropologist [[Mary Leakey]], and in [[Hadar, Ethiopia|Hadar]], Ethiopia, from 1972 to 1977 by the International Afar Research Expedition (IARE) formed by French geologist [[Maurice Taieb]], American palaeoanthropologist [[Donald Johanson]] and Breton anthropologist [[Yves Coppens]]. These fossils were remarkably well preserved and many had associated skeletal aspects.<ref name=Kimbel2009>{{cite journal|first1=W. H.|last1=Kimbel|first2=L. K.|last2=Delezene|year=2009|title="Lucy" Redux: A Review of Research on ''Australopithecus afarensis''|journal=American Journal of Physical Anthropology|volume=49|doi=10.1002/ajpa.21183|pmid=19890859|pages=2–48|doi-access=free}}</ref>{{rp|5}} In 1973, the IARE team unearthed the first [[knee joint]], [[AL 129-1]], and showed the earliest example at the time of [[bipedalism]]. On 24 November 1974, Johanson and graduate student Tom Gray discovered the extremely well-preserved skeleton AL 288–1, commonly referred to as "[[Lucy (Australopithecus)|Lucy]]" (named after the 1967 [[The Beatles|Beatles]] song ''[[Lucy in the Sky with Diamonds]]'' which was playing on their [[tape recorder]] that evening).<ref name=Johanson1990>{{cite book|first=D.|last=Johanson|author-link=Donald Johanson|year=1990|chapter=Prologue|title=Lucy: The Beginnings of Humankind|publisher=Simon and Schuster|isbn=978-0-671-72499-3}}</ref> In 1975, the IARE recovered 216 specimens belonging to 13 individuals, [[AL 333]] "the First Family" (though the individuals were not necessarily related).<ref>{{cite journal|first=D. C.|last=Johanson|author-link=Donald Johanson|year=2004|title=Lucy, Thirty Years Later: An Expanded View of ''Australopithecus afarensis''|journal=Journal of Anthropological Research|volume=60|issue=4|doi=10.1086/jar.60.4.3631138|jstor=3631138|pages=465–486|s2cid=159745450}}</ref>{{rp|471–472}} In 1976, Leakey and colleagues discovered [[fossil trackway]]s, and preliminarily classified Laetoli remains into ''[[Homo]]'' spp., attributing ''Australopithecus''-like traits as evidence of them being [[transitional fossil]]s.<ref>{{cite journal|first1=M.|last1=Leakey|author-link=Mary Leakey|first2=R. H.|last2=Ray|first3=G. H.|last3=Curtis|first4=R. E.|last4=Drake|first5=M. K.|last5=Jackes|first6=T. D.|last6=White|author6-link=Tim D. White|year=1976|title=Fossil hominids from the Laetolil Beds|journal=Nature|volume=262|issue=5568|pages=460–466|doi=10.1038/262460a0|pmid=822342|bibcode=1976Natur.262..460L|hdl=2027.42/62755|s2cid=4151505|hdl-access=free}}</ref>

[[File:LH 4 Replica 03.jpg|thumb|left|The [[holotype]] [[LH 4]]]]
In 1978, Johanson, [[Tim D. White]] and Coppens classified the hundreds of specimens collected thus far from both Hadar and Laetoli into a single new species, ''A. afarensis'', and considered the apparently wide range of variation a result of [[sexual dimorphism]]. The [[specific name (zoology)|specific name]] honours the [[Afar Region]] of Ethiopia where the majority of the specimens had been recovered from and replaces Weinert's ''africanus'', which was already [[Homonym (biology)|preoccupied]] by ''Australopithecus africanus''. They later selected the jawbone [[LH 4]] as the [[holotype specimen]] because of its preservation quality and because White had already fully described and illustrated it the year before.<ref name=Johanson1978/>

[[File:Afarensis east Africa.jpg|thumb|left|200px|Locations of ''A. afarensis'' sites]]
''A. afarensis'' is known only from [[East Africa]]. Beyond Laetoli and the Afar Region, the species has been recorded in Kenya at [[Koobi Fora]] and possibly [[Lothagam]]; and elsewhere in Ethiopia at Woranso-Mille, Maka, Belohdelie, [[Ledi-Geraru]] and Fejej.<ref name=Behrensmeyer2013/><ref name=Delson2004/> The [[frontal bone]] fragment BEL-VP-1/1 from the [[Middle Awash]],<ref>{{citation |title=Facts about the Oromo of East Africa |date=May 26, 1995 |url=https://www.africa.upenn.edu/Articles_Gen/Oromo.html |archive-url=https://web.archive.org/web/20210128081800/https://www.africa.upenn.edu/Articles_Gen/Oromo.html |access-date=April 6, 2021 |archive-date=January 28, 2021 |url-status=live}}</ref> Afar Region, Ethiopia, dating to 3.9 million years ago has typically been assigned to ''A. anamensis'' based on age, but may be assignable to ''A. afarensis'' because it exhibits a [[synapomorphy and apomorphy|derived]] form of [[postorbital constriction]]. This would mean ''A. afarensis'' and ''A. anamensis'' coexisted for at least 100,000 years.<ref name=Haile2019/> In 2005, a second adult specimen preserving both skull and body elements, AL 438–1, was discovered in Hadar.<ref>{{cite journal|first1=M. S. M.|last1=Drapeau|first2=C. V.|last2=Ward|first3=W. H.|last3=Kimbel|first4=D. C.|last4=Johanson|author4-link=Donald Johanson|first5=Y.|last5=Rak|year=2005|title=Associated Cranial and Forelimb Remains Attributed to ''Australopithecus afarensis'' From Hadar, Ethiopia|journal=Journal of Human Evolution|volume=48|issue=6|pages=593–642|doi=10.1016/j.jhevol.2005.02.005|pmid=15927662|bibcode=2005JHumE..48..593D }}</ref> In 2006, an infant partial skeleton, [[DIK-1-1]], was unearthed at [[Dikika]], Afar Region.<ref name=Alamseged2006>{{cite journal|first1=Z.|last1=Alamseged|first2=F.|last2=Spoor|first3=W. H.|last3=Kimbel|first4=R.|last4=Bobe|first5=D.|last5=Geraads|first6=D.|last6=Reed|first7=J. G.|last7=Wynn|year=2006|title=A juvenile early hominin skeleton from Dikika, Ethiopia|journal=Nature|volume=443|issue=7109|pages=296–301|doi=10.1038/nature05047|pmid=16988704|bibcode=2006Natur.443..296A|s2cid=4418369}}</ref> In 2015, an adult partial skeleton, [[KSD-VP-1/1]], was recovered from Woranso-Mille.<ref name=Haile2015/>{{rp|1–4}}

For a long time, ''A. afarensis'' was the oldest known African [[great ape]] until the 1994 description of the 4.4-million-year-old ''[[Ardipithecus ramidus]]'',<ref name="Suwa_2009">{{cite journal | title=The ''Ardipithecus ramidus skull'' and its implications for hominid origins | journal=Science | last1=Suwa | first1=G | date=2 October 2009| volume=326 | issue=5949 | pages=68, 68e1–68e7 | doi=10.1126/science.1175825 | last2=Asfaw | first2=B. | last3=Kono | first3=R. T. | last4=Kubo | first4=D. | last5=Lovejoy | first5=C. O. | last6=White | first6=T. D. | pmid=19810194|bibcode = 2009Sci...326...68S | s2cid=19725410 |display-authors=et al.| url=http://doc.rero.ch/record/211453/files/PAL_E4442.pdf }}</ref> and a few earlier or contemporary taxa have been described since, including the 4-million-year-old ''A. anamensis'' in 1995,<ref>{{cite journal |first1=M. G. |last1=Leakey |author-link=Meave G. Leakey |first2=C. S. |last2=Feibel |first3=I. |last3=MacDougall |first4=A. |author3-link=Ian McDougall (geologist) |last4=Walker |author4-link=Alan Walker (anthropologist) |year=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> the 3.5-million-year-old ''[[Kenyanthropus platyops]]'' in 2001,<ref>{{cite journal|last1=Leakey|first1=M. G.|author-link=Meave Leakey|display-authors=et al.|year=2001|title=New hominin genus from eastern Africa shows diverse middle Pliocene lineages|journal=Nature|volume=410|issue=6827|pages=433–440|bibcode=2001Natur.410..433L|doi=10.1038/35068500|pmid=11260704|s2cid=4409453}}</ref> the 6-million-year-old ''[[Orrorin tugenensis]]'' in 2001,<ref>{{cite journal |last1=Senut |first1=B. |last2=Pickford |first2=M. |last3=Gommery |first3=D.|last4=Mein |first4=P. |last5=Cheboi |first5=K. |last6=Coppens |first6=Y.|author6-link=Yves Coppens |title=First hominid from the Miocene (Lukeino Formation, Kenya) |journal=Comptes Rendus de l'Académie des Sciences, Série IIA |year= 2001 |volume=332 |issue=2 |pages=137–144 |doi=10.1016/S1251-8050(01)01529-4 |bibcode=2001CRASE.332..137S |s2cid=14235881 }}</ref> and the 7- to 6-million-year-old ''Sahelanthropus tchadensis'' in 2002.<ref name=klages>{{cite journal |last1=Brunet |first1=M. |last2=Guy |first2=F. |last3=Pilbeam |first3=D. |author3-link=David Pilbeam|last4=Mackaye |first4=H. T.|display-authors=et al.|year=2002 |title=A new hominid from the Upper Miocene of Chad, Central Africa |journal=[[Nature (journal)|Nature]] |volume=418 |issue=6894| pages=145–151 |doi=10.1038/nature00879 |pmid=12110880|bibcode=2002Natur.418..145B|s2cid=1316969 |url=http://doc.rero.ch/record/13388/files/PAL_E190.pdf }}</ref> Bipedalism was once thought to have evolved in australopithecines, but it is now thought to have begun evolving much earlier in habitually arboreal primates. The earliest claimed date for the beginnings of an upright spine and a primarily vertical body plan is 21.6 million years ago in the [[Early Miocene]] with ''[[Morotopithecus bishopi]]''.<ref>{{cite journal|title=Homeotic Evolution in the Mammalia: Diversification of Therian Axial Seriation and the Morphogenetic Basis of Human Origins |journal = PLOS ONE|volume = 2|issue = 10|pages = e1019|first=Aaron G. |last=Filler |date=October 10, 2007 |doi=10.1371/journal.pone.0001019 |pmid = 17925867|pmc = 2000357 |bibcode = 2007PLoSO...2.1019F|doi-access = free}}</ref>
{{clear}}

===Classification===
''A. afarensis'' is now a widely accepted species, and it is now generally thought that ''Homo'' and ''Paranthropus'' are [[sister taxa]] deriving from ''Australopithecus'', but the classification of ''Australopithecus'' species is in disarray. ''Australopithecus'' is considered a [[evolutionary grade|grade taxon]] whose members are united by their similar physiology rather than close relations with each other over other hominin genera. It is unclear how any ''Australopithecus'' species relate to each other,<ref name="McNulty2016">{{cite journal|first=K. P.|last=McNulty|year=2016|title=Hominin Taxonomy and Phylogeny: What's In A Name?|journal=Nature Education Knowledge|volume=7|issue=1|page=2|url=https://www.nature.com/scitable/knowledge/library/hominin-taxonomy-and-phylogeny-what-s-in-142102877/}}</ref> but it is generally thought that a population of ''[[A. anamensis]]'' evolved into ''A. afarensis''.<ref name="Haile2019">{{cite journal|last1=Haile-Selassie|first1=Y.|author1-link=Yohannes Haile-Selassie|last2=M. Melillo|first2=S.|last3=Vazzana|first3=A.|last4=Benazzi|first4=S.|last5=T.|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="McNulty2016"/><ref name="Kimbel">{{cite journal |last1=Kimbel |first1=W. H. |last2=Lockwood |first2=C. A. |first3=C. V. |last3=Ward |first4=M. G. |last4=Leakey |author4-link=Meave G. Leakey |first5=Y. |last5=Rake |first6=D. C. |last6=Johanson |author6-link=Donald 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|bibcode=2006JHumE..51..134K }}</ref>

In 1979, Johanson and White proposed that ''A. afarensis'' was the last common ancestor between ''Homo'' and ''[[Paranthropus]]'', supplanting ''A. africanus'' in this role.<ref>{{cite journal|first1=D. C.|last1=Johanson|author-link=Donald Johanson|first2=T. D.|last2=White|author2-link=Tim D. White|year=1979|title=A Systematic Assessment of Early African Hominids|journal=Science|volume=203|issue=4378|pages=321–330|doi=10.1126/science.104384|pmid=104384|bibcode=1979Sci...203..321J}}</ref> Considerable debate of the validity of this species followed, with proposals for [[synonym (taxonomy)|synonymising]] them with ''A. africanus'' or recognising multiple species from the Laetoli and Hadar remains. In 1980, South African palaeoanthropologist [[Phillip V. Tobias]] proposed reclassifying the Laetoli specimens as ''A. africanus afarensis'' and the Hadar specimens as ''A. afr. aethiopicus''.<ref>{{Cite journal|last=Tobias|first=Phillip V.|date=1980|title="Australopithecus afarensis" and A. africanus: Critique and an alternative hypothesis|journal=Palaeontologia Africana|s2cid=81551249}}</ref> The skull KNM-ER 1470 (now ''[[H. rudolfensis]]'') was at first dated to 2.9 million years ago, which cast doubt on the ancestral position of both ''A. afarensis'' or ''A. africanus'', but it has been re-dated to about 2 million years ago.<ref name=Delson2004>{{cite book|first1=E.|last1=Delson|first2=I.|last2=Tattersall|author2-link=Ian Tattersall|first3=J.|last3=Van Couvering|first4=A. S.|last4=Brooks|year=2004|title=Encyclopedia of Human Evolution and Prehistory|edition=2nd|publisher=Routledge|pages=118–120|isbn=978-1-135-58228-9}}</ref> Several ''Australopithecus'' species have since been postulated to represent the ancestor to ''Homo'', but the 2013 discovery of the earliest ''Homo'' specimen, [[LD 350-1]], 2.8 million years old (older than almost all other ''Australopithecus'' species) from the Afar Region could potentially affirm ''A. afarensis''{{'}} ancestral position.<ref name="Villmoare2015">{{cite journal|first1=B.|last1=Villmoare|first2=W. H.|last2=Kimbel|first3=C.|last3=Seyoum|display-authors=et al.|year=2015|title=Early ''Homo'' at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia|journal=Science|volume=347|issue=6228|pages=1352–1355|doi=10.1126/science.aaa1343|doi-access=free|pmid=25739410|bibcode=2015Sci...347.1352V}}</ref> However, ''A. afarensis'' is also argued to have been too derived (too specialised), due to resemblance in jaw anatomy to the robust australopithecines, to have been a human ancestor.<ref name="Rak2007"/>

Palaeoartist [[Walter Ferguson]] has proposed splitting ''A. afarensis'' into "''H. antiquus''", a [[relict population|relict]] [[dryopithecine]] "''Ramapithecus''" (now ''[[Kenyapithecus]]'') and a subspecies of ''A. africanus''. His recommendations have largely been ignored.<ref name=White1994>{{Cite journal|last1=White |first1=T. D.|author-link=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|bibcode=1994Natur.371..306W|issue=6495|s2cid=4347140}}</ref><ref name=Delson2004/> In 2003, Spanish writer [[Camilo José Cela Conde]] and evolutionary biologist [[Francisco J. Ayala]] proposed reinstating "''Praeanthropus''" including ''A. afarensis'' alongside ''[[Sahelanthropus]]'', ''[[A. anamensis]]'', ''[[A. bahrelghazali]]'' and ''[[A. garhi]]''.<ref name="Cela-CondeAyala2003">{{Cite journal | last1 = Cela-Conde | first1 = C. J.|author1-link=Camilo José Cela Conde| last2 = Ayala | first2 = F. J. |author2-link=Francisco J. Ayala| title = Genera of the human lineage | doi = 10.1073/pnas.0832372100 | journal = Proceedings of the National Academy of Sciences | volume = 100 | issue = 13 | pages = 7684–7689 | year = 2003 | pmid = 12794185| pmc = 164648 | bibcode = 2003PNAS..100.7684C| doi-access = free}}</ref> In 2004, Danish biologist Bjarne Westergaard and geologist Niels Bonde proposed splitting off "''Homo hadar''" with the 3.2-million-year-old partial skull AL 333–45 as the holotype, because a foot from the First Family was apparently more humanlike than that of Lucy. In 2011, Bonde agreed with Ferguson that Lucy should be split into a new species, though erected a new genus as "''Afaranthropus antiquus''".<ref>{{cite book|first=N.|last=Bonde|year=2011|title=The Symbolic Species Evolved|chapter=Hominid Diversity and 'Ancestor' Myths|publisher=Springer Nature|isbn=978-94-007-2336-8}}</ref>

In 1996, a 3.6-million-year-old jaw from [[Koro Toro]], Chad, originally classified as ''A. afarensis'' was split off into a new species as ''[[A. bahrelghazali]]''.<ref>{{cite journal|first1=M.|last1=Brunet|author-link=Michel Brunet (paleontologist)|first2=A.|last2=Beauvilain|first3=Y.|last3=Coppens|author3-link=Yves Coppens|last4=Heintz |first4=É. |last5=Moutaye |first5=A. H. E |last6=Pilbeam |first6=D. |author6-link=David Pilbeam|year=1996 |url=https://afanporsaber.com/wp-content/uploads/2017/09/Australopithecus-bahrelghazali-une-nouvelle-esp%C3%A8ce-dHominid%C3%A9-ancien-de-la-r%C3%A9gion-de-Koro-Toro-Tchad.pdf |title=''Australopithecus bahrelghazali'', une nouvelle espèce d'Hominidé ancien de la région de Koro Toro (Tchad) |journal=Comptes Rendus des Séances de l'Académie des Sciences |volume=322 |pages=907–913}}</ref> In 2015, some 3.5- to 3.3-million-year-old jaw specimens from the Afar Region (the same time and place as ''A. afarensis'') were classified as a new species as ''[[A. deyiremeda]]'', and the recognition of this species would call into question the species designation of fossils currently assigned to ''A. afarensis''.<ref>{{Cite journal|doi=10.1038/nature14448|pmid=26017448|title=New species from Ethiopia further expands Middle Pliocene hominin diversity|journal=Nature|volume=521|issue=7553|pages=483–488|year=2015|last1=Haile-Selassie|first1=Y|author1-link=Yohannes Haile-Selassie|last2=Gibert|first2=L.|last3=Melillo|first3=S. M.|last4=Ryan|first4=T. M.|last5=Alene|first5=M.|last6=Deino|first6=A.|last7=Levin|first7=N. E.|last8=Scott|first8=G.|last9=Saylor|first9=B. Z.|bibcode=2015Natur.521..483H|s2cid=4455029}}</ref> However, the validity of ''A. bahrelghazali'' and ''A. deyiremeda'' is debated.<ref>{{cite journal|first1=F.|last1=Spoor|first2=M. G.|last2=Leakey|author2-link=Meave Leakey|first3=P.|last3=O'Higgins|year=2016|title=Middle Pliocene hominin diversity: ''Australopithecus deyiremeda'' and ''Kenyanthropus platyops''|journal=Philosophical Transactions of the Royal Society B|volume=371|issue=1698|page=20150231|doi=10.1098/rstb.2015.0231|pmc=4920288|pmid=27298462}}</ref> Wood and Boyle (2016) stated there was "low confidence" that ''A. afarensis'', ''A. bahrelghazali'' and ''A. deyiremeda'' are distinct species, with ''[[Kenyanthropus|Kenyanthropus platyops]]'' perhaps being indistinct from the latter two.<ref name=":0">{{Cite journal|last1=Wood|first1=Bernard|last2=K. Boyle|first2=Eve|date=January 2016|title=Hominin taxic diversity: Fact or fantasy?: HOMININ TAXIC DIVERSITY|journal=American Journal of Physical Anthropology|language=en|volume=159|issue=Suppl 61|pages=37–78|doi=10.1002/ajpa.22902|pmid=26808110|doi-access=free}}</ref>
{{African hominin timeline}}
==Anatomy==
===Skull===
{{Multiple image|total_width=380|image1=BH-021-T-A-afarensis-Lucy-3qtrR-Lo.jpg|image2=Australopithecus afarensis skull - Naturmuseum Senckenberg - DSC02102.JPG|footer=Two ''A. afarensis'' skulls}}

''A. afarensis'' had a tall face, a delicate brow ridge, and [[prognathism]] (the jaw jutted outwards). One of the biggest skulls, AL 444–2, is about the size of a female gorilla skull.<ref>{{cite book|first1=W. H.|last1=Kimbel|first2=Y.|last2=Yak|first3=D. C.|last3=Johanson|author3-link=Donald Johanson|chapter=A. L. 444-2: the skull as a whole|title=The skull of Australopithecus afarensis|date=11 March 2004|publisher=Oxford University Press|isbn=978-0-19-803569-5}}</ref> The first relatively complete jawbone was discovered in 2002, AL 822–1. This specimen strongly resembles the deep and robust gorilla jawbone. However, unlike gorillas, the strength of the [[sagittal crest|sagittal]] and [[nuchal lines|nuchal]] crests (which support the [[temporalis muscle]] used in biting) do not vary between sexes. The crests are similar to those of chimpanzees and female gorillas.<ref name="Rak2007">{{cite journal|first1=Y.|last1=Rak|first2=A.|last2=Ginzburg|first3=E.|last3=Geffen|year=2007|title=Gorilla-like anatomy on ''Australopithecus afarensis'' mandibles suggests ''Au. afarensis'' link to robust australopiths|journal=Proceedings of the National Academy of Sciences|volume=104|issue=16|pages=6568–6572|doi=10.1073/pnas.0606454104|pmid=17426152|bibcode=2007PNAS..104.6568R|pmc=1871826|doi-access=free}}</ref> Compared to earlier hominins, the [[incisor]]s of ''A. afarensis'' are reduced in breadth, the [[canine tooth|canines]] reduced in size and lost the honing mechanism which continually sharpens them, the [[premolar]]s are [[molar (tooth)|molar]]-shaped, and the molars are taller.<ref>{{cite journal|first1=C. V.|last1=Ward|first2=J. M.|last2=Plavcan|first3=F. K.|last3=Manthi|year=2010|title=Anterior dental evolution in the ''Australopithecus anamensis''–''afarensis'' lineage|journal=Philosophical Transactions of the Royal Society B|volume=365|issue=1556|pages=3333–3344|doi=10.1098/rstb.2010.0039|pmc=2981954|pmid=20855307}}</ref> The molars of australopiths are generally large and flat with thick [[tooth enamel|enamel]], which is ideal for crushing hard and brittle foods.<ref>{{cite journal|first1=M. F.|last1=Teaford|first2=P. S.|last2=Ungar|year=2000|title=Diet and the evolution of the earliest human ancestors|journal=Proceedings of the National Academy of Sciences|volume=97|issue=25|pages=13506–13511|doi=10.1073/pnas.260368897|pmid=11095758|bibcode=2000PNAS...9713506T|pmc=17605|doi-access=free}}</ref>

The brain volume of Lucy was estimated to have been 365–417 cc, specimen AL 822-1 about 374–392 cc, AL 333-45 about 486–492 [[cubic centimetre|cc]], and AL 444-2 about 519–526 cc. This would make for an average of about 445 cc. The brain volumes of the infant (about 2.5 years of age) specimens DIK-1-1 and AL 333-105 are 273–277 and 310–315 cc, respectively. Using these measurements, the brain growth rate of ''A. afarensis'' was closer to the growth rate of modern humans than to the faster rate in chimpanzees. Though brain growth was prolonged, the duration was nonetheless much shorter than modern humans, which is why the adult ''A. afarensis'' brain was so much smaller. The ''A. afarensis'' brain was likely organised like non-human ape brains, with no evidence for humanlike brain configuration.<ref>{{cite journal|first1=P.|last1=Gunz|first2=S.|last2=Neubauer|first3=D.|last3=Falk|display-authors=et al.|year=2020|title=''Australopithecus afarensis'' endocasts suggest ape-like brain organization and prolonged brain growth|journal=Science Advances|volume=6|issue=14|page=eaaz4729|doi=10.1126/sciadv.aaz4729|pmid=32270044|pmc=7112758|bibcode=2020SciA....6.4729G|doi-access=free}}</ref>

===Size===
{{Multiple image|align=left|total_width=400px|image1=NHM - Australopithecus afarensis Modell 1.jpg|image2=NHM - Australopithecus afarensis Modell 2.jpg|footer=Reconstruction of a male (left) and female (right) ''A. afarensis'' at the [[Natural History Museum, Vienna]]}}
''A. afarensis'' specimens apparently exhibit a wide range of variation, which is generally explained as marked sexual dimorphism with males much bigger than females. In 1991, American anthropologist [[Henry McHenry (anthropologist)|Henry McHenry]] estimated body size by measuring the joint sizes of the leg bones and scaling down a human to meet that size. This yielded {{cvt|151|cm|ftin}} for a presumed male (AL 333–3), whereas Lucy was {{cvt|105|cm|ftin}}.<ref>{{cite journal|first=H. M.|last=McHenry|author-link=Henry McHenry (anthropologist)|year=1991|title=Femoral Lengths and Stature in Plio-Pleistocene Hominids|journal= American Journal of Physical Anthropology|volume=85|issue=2|pages=149–158|doi=10.1002/ajpa.1330850204|pmid=1882979}}</ref> In 1992, he estimated that males typically weighed about {{cvt|44.6|kg}} and females {{cvt|29.3|kg}} assuming body proportions were more humanlike than [[ape]]like. This gives a male to female body mass ratio of 1.52, compared to 1.22 in modern [[human]]s, 1.37 in [[chimpanzee]]s, and about 2 for [[gorilla]]s and [[orangutan]]s.<ref>{{cite journal|first=H. M.|last=McHenry|author-link=Henry McHenry (anthropologist)|year=1992|title=Body Size and Proportions in Early Hominids|journal= American Journal of Physical Anthropology|volume=87|issue=4|pages=407–431|doi=10.1002/ajpa.1330870404|pmid=1580350}}</ref> However, this commonly cited weight figure used only three presumed-female specimens, of which two were among the smallest specimens recorded for the species. It is also contested if australopiths even exhibited heightened sexual dimorphism at all, which if correct would mean the range of variation is normal body size disparity between different individuals regardless of sex. It has also been argued that the [[femoral head]] could be used for more accurate size modeling, and the femoral head size variation was the same for both sexes.<ref>{{cite journal|first1=P. L.|last1=Reno|first2=R. S.|last2=Meindl|first3=M. A.|last3=McCollum|first4=C. O.|last4=Lovejoy|author4-link=Owen Lovejoy|year=2003|title=Sexual dimorphism in ''Australopithecus afarensis'' was similar to that of modern humans|journal=Proceedings of the National Academy of Sciences|volume=100|issue=16|pages=4404–4409|doi=10.1073/pnas.1133180100|pmid=12878734|bibcode=2003PNAS..100.9404R|pmc=170931|doi-access=free}}</ref>

Lucy is one of the most complete Pliocene hominin skeletons, with over 40% preserved, but she was one of the smaller specimens of her species. Nonetheless, she has been the subject of several body mass estimates since her discovery, ranging from {{cvt|13–42|kg}} for absolute lower and upper bounds. Most studies report ranges within {{cvt|25–37|kg}}.<ref name=Brassey2017>{{cite journal |author1=Brassey, C. A. |author2=O'Mahoney, T. G. |author3=Chamberlain, A. T. |author4=Sellers, W. I. |title=A volumetric technique for fossil body mass estimation applied to ''Australopithecus afarensis'' |journal=[[Journal of Human Evolution]] |volume=115 |page=51|year=2018 |doi=10.1016/j.jhevol.2017.07.014 |pmid=28838563 |bibcode=2018JHumE.115...47B |url=https://e-space.mmu.ac.uk/618976/2/deleted_HUMEV-T-16-00432R3.pdf }}</ref>

For the five makers of the Laetoli fossil trackways (S1, S2, G1, G2 and G3), based on the relationship between footprint length and bodily dimensions in modern humans, S1 was estimated to have been considerably large at about {{cvt|165|cm|ftin}} tall and {{cvt|45|kg}} in weight, S2 {{cvt|145|cm|ftin}} and {{cvt|39.5|kg}}, G1 {{cvt|114|cm|ftin}} and {{cvt|30|kg}}, G2 {{cvt|142|cm|ftin}} and {{cvt|39|kg}}, and G3 {{cvt|132|cm|ftin}} and {{cvt|35|kg}}. Based on these, S1 is interpreted to have been a male, and the rest females (G1 and G3 possibly juveniles), with ''A. afarensis'' being a highly dimorphic species.<ref name=Masao2016/>

===Torso===

DIK-1-1 preserves an oval [[hyoid bone]] (which supports the [[tongue]]) more similar to those of chimpanzees and gorillas than the bar-shaped hyoid of humans and orangutans. This would suggest the presence of [[Larynx|laryngeal]] [[air sac]]s characteristic of non-human African apes (and large [[gibbon]]s).<ref name=Alamseged2006/> Air sacs may lower the risk of hyperventilating when producing faster extended call sequences by rebreathing exhaled air from the air sacs. The loss of these in humans could have been a result of speech and resulting low risk of hyperventilating from normal vocalisation patterns.<ref>{{cite journal|first1=G.|last1=Hewitt|first2=A.|last2=MacLarnon|first3=K. E.|last3=Jones|year=2002|title=The Functions of Laryngeal Air Sacs in Primates: A New Hypothesis|journal=Folia Primatologica|volume=73|issue=2–3|pages=70–94|doi=10.1159/000064786|pmid=12207055|s2cid=17329870}}</ref>

It was previously thought that the australopithecines' spine was more like that of non-human apes than humans, with weak [[neck vertebra]]e. However, the thickness of the neck vertebrae of KSD-VP-1/1 is similar to that of modern humans. Like humans, the series has a bulge and achieves maximum girth at C5 and 6, which in humans is associated with the [[brachial plexus]], responsible for nerves and muscle innervation in the arms and hands. This could perhaps speak to advanced motor functions in the hands of ''A. afarensis'' and competency at precision tasks compared to non-human apes, possibly implicated in stone tool use or production.<ref>{{cite journal|first=M. R.|last=Meyer|year=2015|title=The Spinal Cord in Hominin Evolution|journal=eLS|doi=10.1002/9780470015902.a0027058|url=https://www.researchgate.net/publication/306232081|pages=1–6|isbn=9780470015902}}</ref><ref name=Haile2015/>{{rp|63–111}} However, this could have been involved in head stability or posture rather than dexterity. A.L. 333-101 and A.L. 333-106 lack evidence of this feature. The neck vertebrae of KDS-VP-1/1 indicate that the [[nuchal ligament]], which stabilises the head while distance running in humans and other cursorial creatures, was either not well developed or absent.<ref name=Haile2015/>{{rp|92–95}} KSD-VP-1/1, preserving (among other skeletal elements) six rib fragments, indicates that ''A. afarensis'' had a bell-shaped [[ribcage]] instead of the barrel shaped ribcage exhibited in modern humans. Nonetheless, the constriction at the upper ribcage was not so marked as exhibited in non-human great apes and was quite similar to humans.<ref name=Haile2015/>{{rp|143–153}} Originally, the [[vertebral centra]] preserved in Lucy were interpreted as being the [[thoracic vertebrae|T]]6, T8, T10, T11 and [[lumbar vertebrae|L]]3, but a 2015 study instead interpreted them as being T6, T7, T9, T10 and L3.<ref>{{cite journal|first1=M. R.|last1=Meyer|first2=S. A.|last2=Williams|first3=M. P.|last3=Smith|first4=G. J.|last4=Sawyer|year=2015|title=Lucy's back: Reassessment of fossils associated with the A.L. 288-1 vertebral column|journal=Journal of Human Evolution|volume=84|pages=174–180|doi=10.1016/j.jhevol.2015.05.007|pmid=26058822|bibcode=2015JHumE..85..174M |s2cid=10410978 }}</ref> DIK-1-1 shows that australopithecines had twelve thoracic vertebrae like modern humans instead of thirteen like non-human apes.<ref>{{cite journal|first1=C. V.|last1=Ward|first2=T. K.|last2=Nalley|first3=F.|last3=Spoor|first4=P.|last4=Tafforeau|first5=Z.|last5=Alemseged|year=2017|title=Thoracic Vertebral Count and Thoracolumbar Transition in ''Australopithecus afarensis''|journal=Proceedings of the National Academy of Sciences|volume=114|issue=23|pages=6000–6004|doi=10.1073/pnas.1702229114|pmc=5468642|pmid=28533391|bibcode=2017PNAS..114.6000W |doi-access=free}}</ref> Like humans, australopiths likely had five lumbar vertebrae, and this series was likely long and flexible in contrast to the short and inflexible non-human great ape lumbar series.<ref name=Haile2015>{{cite book|first1=Y.|last1=Haile-Selassie|author1-link=Yohannes Haile-Selassie|first2=D. F.|last2=Su|year=2015|title=The Postcranial Anatomy of Australopithecus afarensis: New Insights from KSD-VP-1/1|series=Vertebrate Paleobiology and Paleoanthropology|publisher=Springer|doi=10.1007/978-94-017-7429-1|isbn=978-94-017-7429-1|s2cid=133164058}}</ref>{{rp|143–153}}

===Upper limbs===
[[File:Lucy Skeleton.jpg|left|thumb|"[[Lucy (Australopithecus)|Lucy]]" skeleton]]
Like other australopiths, the ''A. afarensis'' skeleton exhibits a mosaic anatomy with some aspects similar to modern humans and others to non-human great apes. The pelvis and leg bones clearly indicate weight-bearing ability, equating to habitual bipedalism, but the upper limbs are reminiscent of orangutans, which would indicate [[arboreal]] locomotion. However, this is much debated, as tree-climbing adaptations could simply be basal traits inherited from the great ape [[last common ancestor]] in the absence of major selective pressures at this stage to adopt a more humanlike arm anatomy.<ref>{{cite journal|first1=J.|last1=Arias-Martorell|first2=J. M.|last2=Potau|first3=G.|last3=Bello-Hellegouarch|first4=A.|last4=Pérez-Pérez|year=2015|title=Like Father, Like Son: Assessment of the Morphological Affinities of A.L. 288–1 (''A. afarensis''), Sts 7 (''A. africanus'') and Omo 119–73–2718 (''Australopithecus'' sp.) through a Three-Dimensional Shape Analysis of the Shoulder Joint|journal=PLOS ONE|volume=10|issue=2|page=e0117408|doi=10.1371/journal.pone.0117408|pmc=4317181|pmid=25651542|bibcode=2015PLoSO..1017408A|doi-access=free}}</ref>

The shoulder joint is somewhat in a shrugging position, closer to the head, like in non-human apes.<ref name=Green2012/> Juvenile modern humans have a somewhat similar configuration, but this changes to the normal human condition with age; such a change does not appear to have occurred in ''A. afarensis'' development. It was once argued that this was simply a byproduct of being a small-bodied species, but the discovery of the similarly sized ''[[H. floresiensis]]'' with a more or less human shoulder configuration and larger ''A. afarensis'' specimens retaining the shrugging shoulders show this to not have been the case. The [[spine of scapula|scapular spine]] (reflecting the strength of the back muscles) is closer to the range of gorillas.<ref name=Green2012>{{Cite journal | last1 = Green | first1 = D. J. | last2 = Alemseged | first2 = Z. | doi = 10.1126/science.1227123 | title = ''Australopithecus afarensis'' Scapular Ontogeny, Function, and the Role of Climbing in Human Evolution | journal = Science | volume = 338 | issue = 6106 | pages = 514–517 | year = 2012 | pmid =  23112331|bibcode = 2012Sci...338..514G | s2cid = 206543814 }}</ref>

The forearm of ''A. afarensis'' is incompletely known, yielding various brachial indexes ([[radius (bone)|radial]] length divided by [[humeral]] length) comparable to non-human great apes at the upper estimate and to modern humans at the lower estimate. The most complete [[ulna]] specimen, AL 438–1, is within the range of modern humans and other African apes. However, the L40-19 ulna is much longer, though well below that exhibited in orangutans and gibbons. The AL 438-1 [[metacarpals]] are proportionally similar to those of modern humans and orangutans.<ref>{{cite journal|first1=M. S. M.|last1=Drapeau|first2=C. V.|last2=Ward|year=2007|title=Forelimb Segment Length Proportions in Extant Hominoids and ''Australopithecus afarensis''|journal=American Journal of Physical Anthropology|volume=132|issue=3|pages=327–343|doi=10.1002/ajpa.20533|pmid=17154362}}</ref> The ''A. afarensis'' hand is quite humanlike, though there are some aspects similar to orangutan hands which would have allowed stronger flexion of the fingers, and it probably could not handle large spherical or cylindrical objects very efficiently. Nonetheless, the hand seems to have been able to have produced a [[precision grip]] necessary in using [[stone tool]]s.<ref>{{cite journal|first=M. W.|last=Marzke|year=1983|title=Joint functions and grips of the ''Australopithecus afarensis'' hand, with special reference to the region of the capitate|journal=Journal of Human Evolution|volume=12|issue=2|pages=197–211|doi=10.1016/S0047-2484(83)80025-6|bibcode=1983JHumE..12..197M }}</ref> However, it is unclear if the hand was capable of producing stone tools.<ref>{{cite journal|first1=M.|last1=Domalain|first2=A.|last2=Bertin|first3=G.|last3=Daver|year=2017|title=Was ''Australopithecus afarensis'' able to make the Lomekwian stone tools? Towards a realistic biomechanical simulation of hand force capability in fossil hominins and new insights on the role of the fifth digit|journal=Comptes Rendus Palevol|volume=16|issue=5–6|pages=572–584|doi=10.1016/j.crpv.2016.09.003|bibcode=2017CRPal..16..572D |doi-access=free}}</ref>

===Lower limbs===
The australopith pelvis is [[pelvis#Caldwell–Moloy classification|platypelloid]] and maintains a relatively wider distance between the [[hip socket]]s and a more oval shape. Despite being much smaller, Lucy's [[pelvic inlet]] is {{cvt|132|mm}} wide, about the same breadth as that of a modern human woman. These were likely adaptations to minimise how far the [[centre of mass]] drops while walking upright in order to compensate for the short legs (rotating the hips may have been more important for ''A. afarensis''). Likewise, later ''Homo'' could reduce relative pelvic inlet size probably due to the elongation of the legs. Pelvic inlet size may not have been due to fetal head size (which would have increased [[birth canal]] and thus pelvic inlet width) as an ''A. afarensis'' newborn would have had a similar or smaller head size compared to that of a newborn chimpanzee.<ref name=Gruss2015/><ref>{{cite journal|first=Y.|last=Rak|year=1991|title=Lucy's pelvic anatomy: its role in bipedal gait|journal=Journal of Human Evolution|volume=20|issue=4|pages=283–290|doi=10.1016/0047-2484(91)90011-J|bibcode=1991JHumE..20..283R }}</ref> It is debated if the platypelloid pelvis provided poorer leverage for the [[hamstring]]s or not.<ref name=Gruss2015>{{cite journal|first1=L. T.|last1=Gruss|first2=D.|last2=Schmitt|year=2015|title=The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation|journal=Philosophical Transactions of the Royal Society B|volume=370|issue=1663|page=20140063|pmc=4305164|pmid=25602067|doi=10.1098/rstb.2014.0063}}</ref>

[[File:Resti di australopithecus afarensis detto selam, di tre anni circa, da dikika (afar), 3,3 milioni di anni fa.jpg|thumb|upright=1.5|[[DIK-1-1]] skeleton; notice the diverging left big toe bone]]
The [[heel bone]] of ''A. afarensis'' adults and modern humans have the same adaptations for bipedality, indicating a developed grade of walking. The big toe is not dextrous as is in non-human apes (it is adducted), which would make walking more energy efficient at the expense of arboreal locomotion, no longer able to grasp onto tree branches with the feet.<ref name=Latimer&Lovejoy1989>{{cite journal | last1=Latimer | first1=B. | last2=Lovejoy | first2=C. O. | title=The calcaneus of ''Australopithecus afarensis'' and its implications for the evolution of bipedality | journal=American Journal of Physical Anthropology |volume=78 |issue=3 |pages=369–386 |year=1989 |doi=10.1002/ajpa.1330780306 |pmid=2929741 }}</ref> However, the foot of the infantile specimen DIK-1-1 indicates some mobility of the big toe, though not to the degree in non-human primates. This would have reduced walking efficiency, but a partially dextrous foot in the juvenile stage may have been important in climbing activities for food or safety, or made it easier for the infant to cling onto and be carried by an adult.<ref>{{cite journal|first1=J. M.|last1=DeSilva|first2=C. M.|last2=Gill|first3=T. C.|last3=Prang|display-authors=et al.|year=2018|title=A nearly complete foot from Dikika, Ethiopia and its implications for the ontogeny and function of ''Australopithecus afarensis''|journal=Science Advances|volume=4|issue=7|page=eaar7723|doi=10.1126/sciadv.aar7723|pmid=29978043|pmc=6031372|bibcode=2018SciA....4.7723D }}</ref>

==Palaeobiology==
===Diet and technology===
''A. afarensis'' was likely a [[generalist and specialist species|generalist]] [[omnivore]]. [[Isotope analysis#Carbon-13|Carbon isotope analysis]] on teeth from Hadar and Dikika 3.4–2.9 million years ago suggests a widely ranging diet between different specimens, with forest-dwelling specimens showing a preference for [[C3 carbon fixation|C<sub>3</sub> forest plants]], and bush- or [[grassland]]-dwelling specimens a preference for [[C4 carbon fixation|C<sub>4</sub>]] [[Crassulacean acid metabolism|CAM]] savanna plants. C<sub>4</sub> CAM sources include grass, seeds, roots, underground [[storage organ]]s, [[succulents]] and perhaps creatures which ate those, such as [[termite]]s. Thus, ''A. afarensis'' appears to have been capable of exploiting a variety of food resources in a wide range of habitats. In contrast, the earlier ''A. anamensis'' and ''Ar. ramidus'', as well as modern savanna chimpanzees, target the same types of food as forest-dwelling counterparts despite living in an environment where these plants are much less abundant. Few modern primate species consume C<sub>4</sub> CAM plants.<ref>{{cite journal|first1=J. G.|last1=Wynn|first2=M.|last2=Sponheimer|first3=W. H.|last3=Kimbel|display-authors=et al.|year=2013|title=Diet of ''Australopithecus afarensis'' from the Pliocene Hadar Formation, Ethiopia|journal=Proceedings of the National Academy of Sciences|volume=110|issue=26|pages=10495–10500|doi=10.1073/pnas.1222559110|pmid=23733965|pmc=3696813|bibcode=2013PNAS..11010495W|doi-access=free}}</ref> The dental anatomy of ''A. afarensis'' is ideal for consuming hard, brittle foods, but microwearing patterns on the molars suggest that such foods were infrequently consumed, probably as fallback items in leaner times.<ref>{{cite journal|first=P.|last=Ungar|year=2004|title=Dental topography and diets of ''Australopithecus afarensis'' and early ''Homo''|journal=Journal of Human Evolution|volume=46|issue=5|pages=605–622|doi=10.1016/j.jhevol.2004.03.004|pmid=15120268|bibcode=2004JHumE..46..605U }}</ref>

In 2009 at Dikika, Ethiopia, a rib fragment belonging to a cow-sized [[ungulate|hoofed animal]] and a partial femur of a goat-sized juvenile [[bovid]] was found to exhibit cut marks, and the former some crushing, which were initially interpreted as the oldest evidence of butchering with stone tools. If correct, this would make it the oldest evidence of sharp-edged stone tool use at 3.4 million years old, and would be attributable to ''A. afarensis'' as it is the only species known within the time and place.<ref>{{cite journal|first1=S. P.|last1=McPherron|first2=Z.|last2=Alemseged|first3=C. W.|last3=Marean|display-authors=et al.|year=2010|title=Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia|journal=Nature|volume=466|issue=7308|pages=857–860|doi=10.1038/nature09248|pmid=20703305|bibcode=2010Natur.466..857M|s2cid=4356816}}</ref> However, because the fossils were found in a [[sandstone]] unit (and were modified by abrasive sand and gravel particles during the fossilisation process), the attribution to hominin activity is weak.<ref>{{cite journal|first1=M.|last1=Domínguez-Rodrigo|first2=T. R.|last2=Pickering|first3=H. T.|last3=Bunn|year=2010|title=Configurational approach to identifying the earliest hominin butchers|journal=Proceedings of the National Academy of Sciences|volume=107|issue=49|pages=20929–20934|doi=10.1073/pnas.1013711107|pmid=21078985|pmc=3000273|bibcode=2010PNAS..10720929D|doi-access=free}}</ref>

===Society===
It is highly difficult to speculate with accuracy the group dynamics of early hominins.<ref>{{cite journal|first=J. J.|last=Werner|year=2012|title=Mating Behavior in ''Australopithecus'' and Early ''Homo'': A Review of the Diagnostic Potential of Dental Dimorphism|journal=University of Western Ontario Journal of Anthropology|volume=22|issue=1|pages=11–19|url=https://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=1307&context=totem}}</ref> ''A. afarensis'' is typically reconstructed with high levels of sexual dimorphism, with males much larger than females. Using general trends in modern primates, high sexual dimorphism usually equates to a [[Polygyny in animals|polygynous]] society due to intense male–male competition over females, like in the [[harem (zoology)|harem]] society of gorillas. However, it has also been argued that ''A. afarensis'' had much lower levels of dimorphism, and so had a multi-male kin-based society like chimpanzees. Low dimorphism could also be interpreted as having had a [[Monogamy in animals|monogamous]] society with strong male–male competition. Contrarily, the canine teeth are much smaller in ''A. afarensis'' than in non-human primates, which should indicate lower aggression because canine size is generally positively correlated with male–male aggression.<ref>{{cite journal|first=C. S.|last=Larsen|year=2003|title=Equality for the sexes in human evolution? Early hominid sexual dimorphism and implications for mating systems and social behavior|journal=Proceedings of the National Academy of Sciences|volume=100|issue=16|pages=9103–9104|doi=10.1073/pnas.1633678100|pmc=170877|pmid=12886010|bibcode=2003PNAS..100.9103L|doi-access=free}}</ref><ref>{{Cite journal| last1=Reno| first1=P. L.| last2=Lovejoy| first2=C. O.|author2-link=Owen Lovejoy|year=2015| title=From Lucy to Kadanuumuu: balanced analyses of ''Australopithecus afarensis'' assemblages confirm only moderate skeletal dimorphism| journal=PeerJ| volume=3| pages=e925|doi=10.7717/peerj.925|issn=2167-8359|pmc=4419524|pmid=25945314| doi-access=free}}</ref><ref>{{Cite journal| last=Lovejoy|first=C. O.|author-link=Owen Lovejoy|year=2009| title=Reexamining human origins in light of ''Ardipithecus ramidus''| journal=Science |volume=326|issue=5949|pages=74e1–8|issn=1095-9203|pmid=19810200|bibcode=2009Sci...326...74L|doi=10.1126/science.1175834|s2cid=42790876|url=http://doc.rero.ch/record/211449/files/PAL_E4439.pdf}}</ref>

===Birth===
[[File:A Visual Comparison of the Pelvis and Bony Birth Canal Vs. the Size of Infant Skull in Primate Species.png|thumb|left|upright=1.2|Diagram comparing birthing mechanisms of a chimpanzee (left), ''A. afarensis'' (middle) and a modern human (right)]]
The platypelloid pelvis may have caused a different birthing mechanism from modern humans, with the [[neonate]] entering the inlet facing laterally (the head was transversally orientated) until it exited through the [[pelvic outlet]]. This would be a non-rotational birth, as opposed to a fully rotational birth in humans. However, it has been suggested that the shoulders of the neonate may have been obstructed, and the neonate could have instead entered the inlet transversely and then rotated so that it exited through the outlet oblique to the main axis of the pelvis, which would be a semi-rotational birth. By this argument, there may not have been much space for the neonate to pass through the birth canal, causing a difficult [[childbirth]] for the mother.<ref>{{cite journal|first1=J. M.|last1=DeSilva|first2=N. M.|last2=Laudicina|first3=K. R.|last3=Rosenberg|first4=K. R.|last4=Trevathan|year=2017|title=Neonatal Shoulder Width Suggests a Semirotational, Oblique Birth Mechanism in ''Australopithecus afarensis''|journal=The Anatomical Record|volume=300|issue=5|pages=890–899|doi=10.1002/ar.23573|pmid=28406564|doi-access=free}}</ref>

===Gait===
{{Multiple image|direction=vertical|image1=Laetoli footprints S1 and S2.jpg|image2=Test-pit L8 at Laetoli Site S.jpg|footer=Overview of the S1 trackway (above) and image of the L8 test-pit (below)}}
The Laetoli fossil trackway, generally attributed to ''A. afarensis'', indicates a rather developed grade of bipedal locomotion, more efficient than the bent-hip–bent-knee (BHBK) gait used by non-human great apes (though earlier interpretations of the gait include a BHBK posture or a shuffling movement). Trail A consists of short, broad prints resembling those of a two-and-a-half-year-old child, though it has been suggested this trail was made by the extinct bear ''[[Agriotherium|Agriotherium africanus]]''. G1 is a trail consisting of four cycles likely made by a child. G2 and G3 are thought to have been made by two adults.<ref name=Sellers2005/> In 2015, two more trackways were discovered made by one individual, named S1, extending for a total of {{cvt|32|m}}. In 2015, a single footprint from a different individual, S2, was discovered.<ref name=Masao2016>{{cite journal|first1=F. T.|last1=Masao|first2=E. B.|last2=Ichumbaki|first3=M.|last3=Cherin|display-authors=et al.|year=2016|title=New footprints from Laetoli (Tanzania) provide evidence for marked body size variation in early hominins|journal=eLife|volume=5|page=e19568|doi=10.7554/eLife.19568|pmc=5156529|pmid=27964778 |doi-access=free }}</ref>

The shallowness of the toe prints would indicate a more [[anatomical terms of motion#Flexion and extension|flexed]] limb posture when the foot hit the ground and perhaps a less arched foot, meaning ''A. afarensis'' was less efficient at bipedal locomotion than humans.<ref>{{cite journal|first1=K. G.|last1=Hatala|first2=B.|last2=Demes|first3=B. G.|last3=Richmond|year=2016|title=Laetoli footprints reveal bipedal gait biomechanics different from those of modern humans and chimpanzees|journal=Proceedings of the Royal Society B|volume=283|issue=1836|doi=10.1098/rspb.2016.0235|page=20160235|pmid=27488647|pmc=5013756}}</ref> Some tracks feature a {{cvt|100|mm}} long drag mark probably left by the heel, which may indicate the foot was lifted at a low angle to the ground. For push-off, it appears weight shifted from the heel to the side of the foot and then the toes. Some footprints of S1 either indicate asymmetrical walking where weight was sometimes placed on the anterolateral part (the side of the front half of the foot) before toe-off, or sometimes the upper body was rotated mid-step. The angle of gait (the angle between the direction the foot is pointing in on touchdown and median line drawn through the entire trackway) ranges from 2–11° for both right and left sides. G1 generally shows wide and asymmetrical angles, whereas the others typically show low angles.<ref name=Masao2016/>

The speed of the track makers has been variously estimated depending on the method used, with G1 reported at 0.47, 0.56, 0.64, 0.7 and 1&nbsp;m/s (1.69, 2, 2.3, 2.5 and 3.6&nbsp;km/h; 1.1, 1.3, 1.4, 1.6 and 2.2&nbsp;mph); G2/3 reported at 0.37, 0.84 and 1&nbsp;m/s (1.3, 2.9 and 3.6&nbsp;km/h; 0.8, 1.8 and 2.2&nbsp;mph);<ref name=Sellers2005>{{cite journal|first1=W. I.|last1=Sellers|first2=G. M.|last2=Cain|first3=W.|last3=Wang|first4=R. H.|last4=Crompton|year=2005|title=Stride lengths, speed and energy costs in walking of ''Australopithecus afarensis'': using evolutionary robotics to predict locomotion of early human ancestors|journal=Journal of the Royal Society Interface|volume=2|issue=5|doi=10.1098/rsif.2005.0060|pages=431–441|pmid=16849203|pmc=1618507}}</ref><ref name=Masao2016/> and S1 at {{cvt|0.51 or 0.93|m/s|km/h mph}}.<ref name=Masao2016/> For comparison, modern humans typically walk at {{cvt|1–1.7|m/s|km/h mph}}.<ref name=Sellers2005/>

The average step distance is {{cvt|568|mm|ft|2}}, and stride distance {{cvt|1139|mm|ft|2}}. S1 appears to have had the highest average step and stride length of, respectively, {{cvt|505–660|mm2}} and {{cvt|1044–1284|mm|ft|2}} whereas G1–G3 averaged, respectively, 416, 453 and 433&nbsp;mm (1.4, 1.5 and 1.4&nbsp;ft) for step and 829, 880 and 876&nbsp;mm (2.7, 2.9 and 2.9&nbsp;ft) for stride.<ref name=Masao2016/>

''A. afarensis'' was also capable of bipedal running with absolute speeds of {{convert|1.74|-|4.97|m/s|km/h mph|sp=us}}, slower than modern humans with maximum running speeds up to {{convert|7.9|m/s|km/h mph|sp=us}}, and its running energetics was similar to those of mammals and birds of similar body size. It has been suggested that the bipedal gait evolved specifically to improve running rather than to just enhance walking.<ref>{{Cite journal|last1=Bates |first1=K. T. |last2=McCormack |first2=S. |last3=Donald |first3=E. |last4=Coatham |first4=S. |last5=Brassey |first5=C. A. |last6=Charles |first6=J. |last7=O'Mahoney |first7=T. |last8=van Bijlert |first8=P. A. |last9=Sellers |first9=W. I. |year=2024 |title=Running performance in ''Australopithecus afarensis'' |journal=Current Biology |volume=35 |issue=1 |pages=224–230.e4 |doi=10.1016/j.cub.2024.11.025 |doi-access=free |pmid=39701094 }}</ref>

===Pathology===
Australopithecines, in general, seem to have had a high incidence rate of vertebral pathologies, possibly because their vertebrae were better adapted to withstand suspension loads in climbing than compressive loads while walking upright.<ref name=Haile2015/>{{rp|95–97}} Lucy presents marked thoracic [[kyphosis]] (hunchback) and was diagnosed with [[Scheuermann's disease]], probably caused by overstraining her back, which can lead to a hunched posture in modern humans due to irregular curving of the spine. Because her condition presented quite similarly to that seen in modern human patients, this would indicate a basically human range of locomotor function in walking for ''A. afarensis''. The original straining may have occurred while climbing or swinging in the trees, though, even if correct, this does not indicate that her species was maladapted for arboreal behaviour, much like how humans are not maladapted for bipedal posture despite developing [[arthritis]].<ref>{{cite journal|first1=D. C.|last1=Cook|first2=J. E.|last2=Buikstra|first3=C. J.|last3=DeRousseau|first4=D. C.|last4=Johanson|author4-link=Donald Johanson|title=Vertebral Pathology in the Afar Australopithecines|journal=American Journal of Physical Anthropology|volume=60|issue=1|pages=83–101|doi=10.1002/ajpa.1330600113|year=1983|pmid=6408925}}</ref> KSD-VP-1/1 seemingly exhibits compensatory action by the neck and lumbar vertebrae (gooseneck) consistent with thoracic kyphosis and Scheuermann's disease, but thoracic vertebrae are not preserved in this specimen.<ref name=Haile2015/>{{rp|95–97}}

In 2010, KSD-VP-1/1 presented evidence of a [[valgus deformity]] of the left ankle involving the [[fibula]], with a bony ring developing on the fibula's joint surface extending the bone an additional {{cvt|5–10|mm}}. This was probably caused by a [[fibular fracture]] during childhood which improperly healed in a [[nonunion]].<ref name=Haile2015/>{{rp|162–163}}

In 2016, palaeoanthropologist John Kappelman argued that the fracturing exhibited by Lucy was consistent with a [[proximal humerus fracture]], which is most often caused by falling in humans. He then concluded she died from falling out of a tree, and that ''A. afarensis'' slept in trees or climbed trees to escape predators. However, similar fracturing is exhibited in many other creatures in the area, including the bones of [[antelope]], [[elephant]]s, [[giraffe]]s and [[rhino]]s, and may well simply be [[taphonomic bias]] (fracturing was caused by fossilisation).<ref>{{cite journal|first=A.|last=Gibbons|year=2016|title=Did famed human ancestor 'Lucy' fall to her death?|journal=Science|doi=10.1126/science.aah7237}}</ref> Lucy may also have been killed in an animal attack or a [[mudslide]].<ref>{{cite journal|first1=P.|last1=Charlier|first2=Y.|last2=Coppens|author2-link=Yves Coppens|first3=A.|last3=Augias|display-authors=et al.|year=2018|title=Mudslide and/or animal attack are more plausible causes and circumstances of death for AL 288 ('Lucy'): A forensic anthropology analysis|journal=Medico-Legal Journal|volume=86|issue=3|pages=139–142|doi=10.1177/0025817217749504|pmid=29313437|s2cid=20995655}}</ref>

The 13 AL 333 individuals are thought to have been deposited at about the same time as one another, bear little evidence of carnivore activity, and were buried on a {{cvt|7|m|adj=on}} stretch of a hill. In 1981, anthropologists James Louis Aronson and Taieb suggested they were killed in a [[flash flood]]. British archaeologist [[Paul Pettitt]] considered natural causes unlikely and, in 2013, speculated that these individuals were purposefully hidden in tall grass by other hominins (funerary caching).<ref>{{cite book|first=P.|last=Pettitt|author-link=Paul Pettitt|year=2013|title=The Palaeolithic Origins of Human Burial|publisher=Routledge|pages=44–45|isbn=978-1-136-69910-8}}</ref> This behaviour has been documented in modern primates, and may be done so that the recently deceased do not attract predators to living grounds.<ref>{{cite journal|first1=P.|last1=Pettitt|author-link=Paul Pettitt|first2=J. R.|last2=Anderson|year=2019|title=Primate thanatology and hominoid mortuary archeology|journal=Primates|volume=61|issue=1|page=10|doi=10.1007/s10329-019-00769-2|pmid=31646398|pmc=6971134|doi-access=free}}</ref>

==Palaeoecology==
''A. afarensis'' was extremely adaptable in its environmental preferences.<ref>{{Cite journal |last=Bedaso |first=Zelalem K. |last2=Wynn |first2=Jonathan G. |last3=Alemseged |first3=Zeresenay |last4=Geraads |first4=Denis |date=January 2013 |title=Dietary and paleoenvironmental reconstruction using stable isotopes of herbivore tooth enamel from middle Pliocene Dikika, Ethiopia: Implication for Australopithecus afarensis habitat and food resources |url=https://www.sciencedirect.com/science/article/pii/S0047248412001649?casa_token=IZ46CjY4Gv8AAAAA:VWmJ3z1bX717bIAJlHufl2DNpPuKu1ySAaKc8Dwy3u4OdVH55zkFZQba8da9w2hG2jv12CmvnYs |journal=[[Journal of Human Evolution]] |language=en |volume=64 |issue=1 |pages=21–38 |doi=10.1016/j.jhevol.2012.05.015 |access-date=29 November 2024 |via=Elsevier Science Direct|url-access=subscription }}</ref> It does not appear to have had a preferred environment and it inhabited a wide range of habitats such as open grasslands or woodlands, shrublands, and lake- or riverside forests.<ref name="Behrensmeyer2013">{{cite book |last1=Behrensmeyer |first1=A. K. |title=The Paleobiology of ''Australopithecus'' |last2=Reed |first2=K. E. |author-link2=Kaye Reed |publisher=Springer Science and Business Media |year=2013 |isbn=978-94-007-5919-0 |editor1-last=Reed |editor1-first=K. E. |editor-link=Kaye Reed |pages=53–54 |chapter=Reconstructing the Habitats of Australopithecus: Paleoenvironments, Site Taphonomy, and Faunas |editor2-last=Fleagle |editor2-first=J. G. |editor3-last=Leakey |editor3-first=R. E. |editor3-link=Richard Leakey}}</ref> Likewise, the animal assemblage varied widely from site to site. The Pliocene of East Africa was warm and wet compared to the preceding [[Miocene]], with the [[dry season]] lasting about four months based on floral, faunal, and geological evidence. The extended [[rainy season]] would have made more desirable foods available to hominins for most of the year.<ref>{{cite book |last1=Reed |first1=K. E. |author-link=Kaye Reed |title=Evolution of the Human Diet: The Known, the Unknown, and the Unknowable |last2=Rector |first2=A. L. |publisher=Oxford University Press |year=2006 |isbn=978-0-19-534601-5 |chapter=African Pliocene Palaeoecology}}</ref> During the Late Pliocene around 4–3 million years ago, Africa featured a greater diversity of large carnivores than today, and australopithecines likely fell prey to these dangerous creatures, including [[hyena]]s, ''[[Panthera]]'', [[Acinonyx|cheetah]]s, and the [[saber-toothed cats]]: ''[[Megantereon]]'', ''[[Dinofelis]]'', ''[[Homotherium]]'' and ''[[Machairodus]]''.<ref>{{cite book|first1=D.|last1=Hart|first2=R.|last2=Sussman|year=2011|chapter=The Influence of Predation on Primate and Early Human Evolution: Impetus for Cooperation|title=Origins of Altruism and Cooperation|pages=19–40|publisher=Springer Science and Business Media|doi=10.1007/978-1-4419-9520-9_3|isbn=978-1-4419-9519-3}}</ref> The extinct hyena ''[[Chasmaporthetes]]'' is believed to have eaten ''A. afarensis'', while it was an unlikely prey item for the species ''Crocuta venustula''.<ref>{{Cite journal |last1=Robinson |first1=Joshua R. |last2=Lazagabaster |first2=Ignacio A. |last3=Rowan |first3=John |last4=Lewis |first4=Margaret E. |last5=Werdelin |first5=Lars |last6=Campisano |first6=Christopher J. |last7=Reed |first7=Kaye E. |date=May 2025 |title=Palaeoecology of the Pliocene large carnivore guild at Hadar, Lower Awash Valley, Ethiopia |url=https://www.sciencedirect.com/science/article/pii/S0047248425000065?casa_token=GddfMOel-pEAAAAA:Xy6Ek24opWhwQgCuX3VgpnUihb95cGbp4ozmHykhU0gKaptOMnvw67hgWngZqOhMwZI7RMdkjgc |journal=[[Journal of Human Evolution]] |language=en |volume=202 |pages=103653 |doi=10.1016/j.jhevol.2025.103653 |access-date=10 April 2025 |via=Elsevier Science Direct}}</ref>

Australopithecines and early ''Homo'' likely preferred cooler conditions than later ''Homo'', as there are no australopithecine sites that were below {{cvt|1000|m}} in elevation at the time of deposition. This would mean that, like chimpanzees, they often inhabited areas with an average diurnal temperature of {{cvt|25|C}}, dropping to {{cvt|10|or|5|C}} at night.<ref name=David2016>{{cite journal|first1=T.|last1=Dávid-Barrett|first2=R. I. M.|last2=Dunbar|year=2016|title=Bipedality and hair loss in human evolution revisited: The impact of altitude and activity scheduling|journal=Journal of Human Evolution|volume=94|doi=10.1016/j.jhevol.2016.02.006|pmc=4874949|pmid=27178459|pages=72–82|bibcode=2016JHumE..94...72D }}</ref> At Hadar, the average temperature from 3.4 to 2.95 million years ago was about {{cvt|20.2|C}}.<ref>{{cite journal|first1=B.|last1=Raymonde|first2=R.|last2=Potts|first3=F.|last3=Chalie|first4=D.|last4=Jolly|year=2004|title=High-Resolution Vegetation and Climate Change Associated with Pliocene ''Australopithecus afarensis''|journal=Proceedings of the National Academy of Sciences|volume=101|issue=33|pages=12125–12129|doi=10.1073/pnas.0401709101|pmid=15304655|pmc=514445|bibcode=2004PNAS..10112125B|doi-access=free}}</ref>

== See also ==
{{div col|colwidth=30em}}
* ''[[Ardipithecus ramidus]]''
* ''[[Australopithecus anamensis]]''
* ''[[Australopithecus bahrelghazali]]''
* ''[[Australopithecus deyiremeda]]''
* ''[[Kenyanthropus]]''
* [[LD 350-1]]
* [[List of fossil sites]] (with link directory)
* [[List of human evolution fossils]] (with images)
* [[Lomekwi]]

{{div col end}}

==References==
{{Reflist|3}}

==Further reading==
* {{cite book|first1=W. H.|last1=Kimbel|first2=Y.|last2=Yak|first3=D. C.|last3=Johanson|author3-link=Donald Johanson|title=The skull of Australopithecus afarensis|date=11 March 2004|publisher=Oxford University Press|isbn=978-0-19-803569-5}}
* {{cite book|first=Y.|last=Rak|year=2014|chapter=''Australopithecus afarensis''|title=The Australopithecine Face|publisher=Academic Press|pages=66–74|isbn=978-1-4832-1980-6}}
* {{cite book|first1=Y.|last1=Haile-Selassie|author1-link=Yohannes Haile-Selassie|first2=D. F.|last2=Su|year=2015|title=The Postcranial Anatomy of Australopithecus afarensis: New Insights from KSD-VP-1/1|series=Vertebrate Paleobiology and Paleoanthropology|publisher=Springer|doi=10.1007/978-94-017-7429-1|isbn=978-94-017-7429-1|s2cid=133164058}}
* {{cite book|first=J. M.|last=Radice-Wood|year=1987|title=The Social Organization of Australopithecus afarensis: A Critical Assessment of Monogamy and a Counter Proposal for the Probability of Polygyny|publisher=California State University}}

==External links==
{{Commons category|Australopithecus afarensis}}
* [http://www.becominghuman.org/ Becoming Human: Paleoanthropology, Evolution and Human Origins]
* [http://www.archaeologyinfo.com/australopithecusafarensis.htm Archaeology Info]. {{Webarchive|url=https://web.archive.org/web/20110516130108/http://www.archaeologyinfo.com/australopithecusafarensis.htm |date=2011-05-16 }}.
* [http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-afarensis The Smithsonian's Human Origins Program]
* [http://humanorigins.si.edu/evidence/human-evolution-timeline-interactive Human Timeline (Interactive)] – [[Smithsonian Institution|Smithsonian]]

{{Human Evolution}}
{{Portal bar|Evolutionary biology|Paleontology}}
{{Taxonbar|from=Q107685}}
{{Authority control}}

[[Category:Australopithecus|afarensis]]
[[Category:Pliocene primates]]
[[Category:Mammals described in 1978]]
[[Category:Fossil taxa described in 1978]]
[[Category:Prehistoric Ethiopia]]
[[Category:Prehistoric Kenya]]
[[Category:Pliocene mammals of Africa]]
[[Category:Tool-using mammals]]
[[Category:Taxa named by Donald Johanson]]
[[Category:Taxa named by Tim D. White]]
[[Category:Archaeology of Eastern Africa]]