Editing Transitional fossil (section)

===''Australopithecus afarensis''===
{{main|Australopithecus afarensis|Human evolution}}
{{see also|List of human evolution fossils}}
[[File:Lucy Skeleton cropped.jpg|thumb|75px|''[[Australopithecus afarensis|A. afarensis]]'' - walking posture]]
The hominid ''Australopithecus afarensis'' represents an evolutionary transition between modern bipedal humans and their quadrupedal [[ape]] ancestors. A number of traits of the ''A. afarensis'' skeleton strongly reflect bipedalism, to the extent that some researchers have suggested that bipedality evolved long before ''A. afarensis''.<ref name="Lovejoy1988">{{cite journal |last=Lovejoy |first=C. Owen |author-link=Owen Lovejoy (anthropologist) |date=November 1988 |title=Evolution of Human walking |url=http://users.clas.ufl.edu/krigbaum/proseminar/Lovejoy_1988_SA.pdf |journal=[[Scientific American]] |volume=259 |issue=5 |pages=82–89 |doi=10.1038/scientificamerican1188-118 |issn=0036-8733 |pmid=3212438 |bibcode=1988SciAm.259e.118L }}</ref> In overall anatomy, the pelvis is far more human-like than ape-like. The [[Ilium (bone)|iliac blades]] are short and wide, the sacrum is wide and positioned directly behind the hip joint, and there is clear evidence of a strong attachment for the [[Rectus femoris muscle|knee extensors]], implying an upright posture.<ref name="Lovejoy1988" />{{rp|122}}

While the [[pelvis]] is not entirely like that of a human (being markedly wide, or flared, with laterally orientated iliac blades), these features point to a structure radically remodelled to accommodate a significant degree of [[bipedalism]]. The [[femur]] angles in toward the knee from the [[hip]]. This trait allows the foot to fall closer to the midline of the body, and strongly indicates habitual bipedal locomotion. Present-day humans, [[orangutan]]s and [[spider monkey]]s possess this same feature. The feet feature [[adducted]] big toes, making it difficult if not impossible to grasp branches with the [[hindlimb]]s. Besides locomotion, ''A. afarensis'' also had a slightly larger brain than a modern [[Common chimpanzee|chimpanzee]]<ref name="SmithsonianHuman">{{cite web |url=http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-afarensis |title=''Australopithecus afarensis'' |website=Human Evolution |publisher=[[Smithsonian Institution]]'s Human Origins Program |location=Washington, D.C. |access-date=2015-05-15}}</ref> (the closest living relative of humans) and had teeth that were more human than ape-like.<ref>{{cite journal |last1=White |first1=Tim D. |author-link1=Tim D. White |last2=Suwa |first2=Gen |last3=Simpson |first3=Scott |last4=Asfaw |first4=Berhane |author-link4=Berhane Asfaw |date=January 2000 |title=Jaws and teeth of ''Australopithecus afarensis'' from Maka, Middle Awash, Ethiopia |journal=[[American Journal of Physical Anthropology]] |volume=111 |issue=1 |pages=45–68 |doi=10.1002/(SICI)1096-8644(200001)111:1<45::AID-AJPA4>3.0.CO;2-I |issn=0002-9483 |pmid=10618588}}</ref>