Editing Australopithecus (section)

==Anatomy==
The brains of most species of ''Australopithecus'' were roughly 35% of the size of a modern human brain<ref>{{Cite web|url=http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-afarensis|title=Australopithecus afarensis|date=2010-01-25|website=The Smithsonian Institution's Human Origins Program|language=en|access-date=2020-01-09}}</ref> with an [[Brain size|endocranial volume]] average of {{cvt|466|cc}}.<ref name="Kimbel2016" />  Although this is more than the average endocranial volume of [[chimpanzee]] brains at {{cvt|360|cc}}<ref name="Kimbel2016" /> the earliest australopiths (''A. anamensis'') appear to have been within the chimpanzee range,<ref name="Nature573pp214-219" /> whereas some later australopith specimens have a larger endocranial volume than that of some early Homo fossils.<ref name="Kimbel2016" />

Most species of ''Australopithecus'' were diminutive and gracile, usually standing {{convert|1.2|to|1.4|m|abbr=on}} tall. It is possible that they exhibited a considerable degree of [[sexual dimorphism]], males being larger than females.<ref name="Beck1999">{{cite book|url= https://archive.org/details/mcdougallittellw00beck |url-access= registration |last=Beck |first=Roger B. |author2=Linda Black |author3=Larry S. Krieger |author4=Phillip C. Naylor |author5=Dahia Ibo Shabaka |title=World History: Patterns of Interaction |publisher=McDougal Littell |year=1999 |isbn=978-0-395-87274-1 }}</ref> In modern populations, males are on average a mere 15% larger than females, while in ''Australopithecus'', males could be up to 50% larger than females by some estimates. However, the degree of sexual dimorphism is debated due to the fragmentary nature of australopith remains.<ref name="Beck1999" /> One paper finds that ''A. afarensis'' had a level of dimorphism close to modern humans.<ref>Reno, Philip L., Richard S. Meindl, Melanie A. McCollum, and C. Owen Lovejoy. 2003."Sexual Dimorphism in Australopithecus Afarensis Was Similar to That of Modern Humans." Proceedings of the National Academy of Sciences 100 (16): 9404–9. https://doi.org/10.1073/pnas.1133180100.</ref>

According to A. Zihlman, ''Australopithecus'' body proportions closely resemble those of [[bonobo]]s (''Pan paniscus''),<ref>{{cite journal|vauthors=Zihlman AL, Cronin JE, Cramer DL, Sarich VM |year=1978 |title=Pygmy chimpanzee as a possible prototype for the common ancestor of humans, chimpanzees and gorillas |journal=[[Nature (journal)|Nature]] |volume=275 |issue=5682| pages=744–6 |pmid=703839 |doi=10.1038/275744a0 |bibcode=1978Natur.275..744Z |s2cid=4252525 }}</ref> leading evolutionary biologist [[Jeremy Griffith]] to suggest that bonobos may be phenotypically similar to ''Australopithecus''.<ref>{{cite book|last=Griffith|first=Jeremy |author-link=Jeremy Griffith |title=Freedom Book 1|volume= Part 8:4G| year=2013|publisher=WTM Publishing & Communications|isbn=978-1-74129-011-0|url= http://www.worldtransformation.com/freedom-book1-integration-through-love-indoctrination/| access-date=28 March 2013}}</ref> Furthermore, thermoregulatory models suggest that australopiths were fully hair covered, more like chimpanzees and bonobos, and unlike humans.<ref>{{cite journal |last1=David-Barrett |first1=T. |last2=Dunbar |first2=R.I.M. |year=2016 |title=Bipedality and Hair-loss Revisited: The Impact of Altitude and Activity Scheduling |doi=10.1016/j.jhevol.2016.02.006 |journal=[[Journal of Human Evolution]] |volume=94 |pages=72–82 |pmid=27178459 |pmc=4874949}}</ref>

[[File: Australopithecus sediba (Fundort Malapa).jpg|thumb|left|upright=1.3|Reconstruction of a largely hairless male ''[[Australopithecus sediba|A. sediba]]'' by Adrie and Alfons Kennis at the [[Neanderthal Museum]], Germany]]

The fossil record seems to indicate that ''Australopithecus'' is ancestral to ''Homo'' and modern humans. It was once assumed that large brain size had been a precursor to bipedalism, but the discovery of ''Australopithecus'' with a small brain but developed bipedality upset this theory. Nonetheless, it remains a matter of controversy as to how bipedalism first emerged. The advantages of bipedalism were that it left the hands free to grasp objects (e.g., carry food and young), and allowed the eyes to look over tall grasses for possible food sources or predators, but it is also argued that these advantages were not significant enough to cause the emergence of bipedalism.{{citation needed|date=May 2020}} Earlier fossils, such as ''[[Orrorin tugenensis]]'', indicate bipedalism around six million years ago, around the time of the split between humans and chimpanzees indicated by genetic studies. This suggests that erect, straight-legged walking originated as an adaptation to tree-dwelling.<ref>{{cite journal|last1=Thorpe |first1=SK |last2=Holder |first2=RL |last3=Crompton |first3=RH. |year=2007 |title=Origin of human bipedalism as an adaptation for locomotion on flexible branches |journal=[[Science (journal)|Science]] |volume=316 |issue=5829| pages=1328–31 |pmid=17540902 |doi=10.1126/science.1140799|bibcode=2007Sci...316.1328T |s2cid=85992565 }}</ref> Major changes to the pelvis and feet had already taken place before ''Australopithecus''.<ref>{{cite journal |author=Lovejoy, C. O. |title=Evolution of Human walking |journal=[[Scientific American]] |volume=259 |issue=5 |pages=82–89 |year=1988 |doi=10.1038/scientificamerican1188-118 |pmid=3212438|bibcode=1988SciAm.259e.118L }}</ref> It was once thought that humans descended from a [[knuckle-walking]] ancestor,<ref name="Rich01">{{cite journal |pmid=11786992 |last1=Richmond |first1=BG |last2=Begun |first2=DR |last3=Strait |first3=DS |title=Origin of human bipedalism: The knuckle-walking hypothesis revisited |journal=[[American Journal of Physical Anthropology]] |volume=Suppl 33 |year=2001 |pages=70–105 |doi=10.1002/ajpa.10019|doi-access=free }}</ref> but this is not well-supported.<ref name="Kivell">{{cite journal|last1=Kivell |first1=TL |last2=Schmitt |first2=D. |date=Aug 2009 |title=Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=106 |issue=34| pages=14241–6 |doi=10.1073/pnas.0901280106 |pmc=2732797 |pmid=19667206 |bibcode=2009PNAS..10614241K |doi-access=free }}</ref>

Australopithecines have thirty-two teeth, like modern humans. Their molars were parallel, like those of great apes, and they had a slight pre-canine gap (diastema). Their canines were smaller, like modern humans, and with the teeth less interlocked than in previous hominins. In fact, in some australopithecines, the canines are shaped more like incisors.<ref name="Kay1985">Kay, R.F., 1985, 'DENTAL EVIDENCE FOR THE DIET OF ''AUSTRALOPITHECUS''<nowiki/>', ''[[Annual Review of Anthropology]]'', 14, pp. 315-341.</ref> The molars of ''Australopithecus'' fit together in much the same way those of humans do, with low crowns and four low, rounded cusps used for crushing. They have cutting edges on the crests.<ref name="Kay1985" /> However, australopiths generally evolved a larger postcanine dentition with thicker enamel.<ref name="evolutionthe1st4billionyears">{{cite book |title=Evolution: The First Four Billion Years |author=McHenry, H. M. |chapter=Human Evolution |editor=Michael Ruse |editor2=Joseph Travis |year=2009 |publisher=The Belknap Press of Harvard University Press |location=Cambridge, Massachusetts |isbn=978-0-674-03175-3 |pages=[https://archive.org/details/evolutionfirstfo00mich/page/261 261–265] |chapter-url=https://archive.org/details/evolutionfirstfo00mich/page/261 }}</ref> Australopiths in general had thick [[tooth enamel|enamel]], like ''Homo'', while other great apes have markedly thinner enamel.<ref name="Kay1985" /> Robust australopiths wore their molar surfaces down flat, unlike the more gracile species, who kept their crests.<ref name="Kay1985" />