Editing Australopithecus afarensis (section)

===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>