Editing Bipedalism (section)

===Provisioning model===
One theory on the origin of bipedalism is the behavioral model presented by [[Owen Lovejoy (anthropologist)|C. Owen Lovejoy]], known as "male provisioning".<ref name="Price">{{Cite book |author1=T. Douglas Price |author2=Gary M. Feinman |year=2003 |title=Images of the Past, 5th edition |page=[https://archive.org/details/imagesofpast0005pric/page/68 68] |location=Boston, MA |publisher=McGraw Hill |isbn=978-0-07-340520-9 |url=https://archive.org/details/imagesofpast0005pric/page/68}}</ref> Lovejoy theorizes that the [[evolution]] of bipedalism was linked to monogamy. In the face of long inter-birth intervals and low reproductive rates typical of the apes, early [[hominid]]s engaged in pair-bonding that enabled greater parental effort directed towards rearing offspring. Lovejoy proposes that male provisioning of food would improve the offspring survivorship and increase the pair's reproductive rate. Thus the male would leave his mate and offspring to search for food and return carrying the food in his arms walking on his legs. This model is supported by the reduction ("feminization") of the male canine teeth in early hominids such as ''[[Sahelanthropus tchadensis]]''<ref>{{Cite journal |vauthors=Brunet M, Guy F, Pilbeam D, Mackaye HT, Likius A |title=A new hominid from the Upper Miocene of Chad, Central Africa |journal=Nature |date=11 July 2002 |volume=418 |pages=145–151 |doi=10.1038/nature00879 |pmid=12110880 |issue=6894 |display-authors=etal |bibcode=2002Natur.418..145B |s2cid=1316969|url=http://doc.rero.ch/record/13388/files/PAL_E190.pdf }}</ref> and ''[[Ardipithecus ramidus]]'',<ref>{{Cite journal |vauthors=Suwa G, Kono RT, Simpson SW, Asfaw B, Lovejoy CO, White TD |title=Paleobiological implications of the ''Ardipithecus ramidus'' dentition |journal=Science |date=2 October 2009 |volume=326 |issue=5949 |pages=94–99 |doi=10.1126/science.1175824 |pmid=19810195 |bibcode=2009Sci...326...94S |s2cid=3744438 |url=http://doc.rero.ch/record/211460/files/PAL_E4443.pdf |url-status=live |archive-date=2022-10-09 |archive-url=https://ghostarchive.org/archive/20221009/http://doc.rero.ch/record/211460/files/PAL_E4443.pdf}}</ref> which along with low body size dimorphism in ''Ardipithecus''<ref>{{cite journal |vauthors=White TD |title=Ardipithecus ramidus and the paleobiology of early hominids |display-authors=et al |journal=Science |date=2009 |volume=326 |issue=5949 |pages=75–86|doi=10.1126/science.1175802 |pmid=19810190 |bibcode=2009Sci...326...75W |s2cid=20189444 }}</ref> and ''Australopithecus'',<ref>{{cite journal |vauthors=Reno PL |title=An enlarged postcranial sample confirms Australopithecus afarensis dimorphism was similar to modern humans |display-authors=et al |journal=Philos Trans R Soc Lond B Biol Sci |date=2010 |volume=365 |issue=1556 |pages=3355–3363|doi=10.1098/rstb.2010.0086 |pmid=20855309 |pmc=2981962 }}</ref><ref>{{cite journal |vauthors=Harmon E |title=Size and shape variation in the proximal femur of Australopithecus africanus |journal=J Hum Evol |date=2009 |volume=56 |issue=6 |pages=551–559|doi=10.1016/j.jhevol.2009.01.002 |pmid=19446306 |bibcode=2009JHumE..56..551H }}</ref><ref>{{cite journal |vauthors=Reno PL, Lovejoy CO |title=From Lucy to Kadanuumuu: Balanced analyses of ''Australopithecus'' afarensisassemblages confirm only moderate skeletal dimorphism |journal=PeerJ |date=2015 |volume=3 |at=e925 |doi=10.7717/peerj.925|pmid=25945314 |pmc=4419524 |doi-access=free }}</ref> suggests a reduction in inter-male antagonistic behavior in early hominids.<ref name="ReferenceB">{{cite journal |vauthors=Lovejoy CO |title=Reexamining human origins in light of Ardipithecus ramidus |journal=Science |date=2009 |volume=326 |issue=5949 |pages=74e1–8 |doi=10.1126/science.1175834 |pmid=19810200 |bibcode=2009Sci...326...74L |s2cid=42790876 |url=http://doc.rero.ch/record/211449/files/PAL_E4439.pdf }}</ref> In addition, this model is supported by a number of modern human traits associated with concealed ovulation (permanently enlarged breasts, lack of [[sexual swelling]]) and low sperm competition (moderate sized testes, low sperm mid-piece volume) that argues against recent adaptation to a polygynous reproductive system.<ref name="ReferenceB"/>

However, this model has been debated, as others have argued that early bipedal hominids were instead polygynous. Among most monogamous primates, males and females are about the same size. That is [[sexual dimorphism]] is minimal, and other studies have suggested that ''[[Australopithecus afarensis]]'' males were nearly twice the weight of females. However, Lovejoy's model posits that the larger range a provisioning male would have to cover (to avoid competing with the female for resources she could attain herself) would select for increased male body size to limit predation risk.<ref>{{Cite journal |vauthors=Lovejoy CO |title=The Origin of Man |journal=Science |year=1981 |volume=211 |issue=4480 |pages=341–350 |doi=10.1126/science.211.4480.341 |pmid=17748254 |bibcode=1981Sci...211..341L}}</ref> Furthermore, as the species became more bipedal, specialized feet would prevent the infant from conveniently clinging to the mother{{snd}} hampering the mother's freedom<ref>{{cite book |author1=Keith Oatley |author2=Dacher Keltner |author3=Jennifer M. Jenkins |title=Understanding Emotion |year=2006 |edition=2nd |page=235}}</ref> and thus make her and her offspring more dependent on resources collected by others. Modern monogamous primates such as gibbons tend to be also territorial, but fossil evidence indicates that ''Australopithecus afarensis'' lived in large groups. However, while both gibbons and hominids have reduced canine sexual dimorphism, female gibbons enlarge ('masculinize') their canines so they can actively share in the defense of their home territory. Instead, the reduction of the male hominid canine is consistent with reduced inter-male aggression in a pair-bonded though group living primate.