Editing Australopithecus afarensis (section)

===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>