Editing Australopithecus afarensis (section)

===Torso===

DIK-1-1 preserves an oval [[hyoid bone]] (which supports the [[tongue]]) more similar to those of chimpanzees and gorillas than the bar-shaped hyoid of humans and orangutans. This would suggest the presence of [[Larynx|laryngeal]] [[air sac]]s characteristic of non-human African apes (and large [[gibbon]]s).<ref name=Alamseged2006/> Air sacs may lower the risk of hyperventilating when producing faster extended call sequences by rebreathing exhaled air from the air sacs. The loss of these in humans could have been a result of speech and resulting low risk of hyperventilating from normal vocalisation patterns.<ref>{{cite journal|first1=G.|last1=Hewitt|first2=A.|last2=MacLarnon|first3=K. E.|last3=Jones|year=2002|title=The Functions of Laryngeal Air Sacs in Primates: A New Hypothesis|journal=Folia Primatologica|volume=73|issue=2–3|pages=70–94|doi=10.1159/000064786|pmid=12207055|s2cid=17329870}}</ref>

It was previously thought that the australopithecines' spine was more like that of non-human apes than humans, with weak [[neck vertebra]]e. However, the thickness of the neck vertebrae of KSD-VP-1/1 is similar to that of modern humans. Like humans, the series has a bulge and achieves maximum girth at C5 and 6, which in humans is associated with the [[brachial plexus]], responsible for nerves and muscle innervation in the arms and hands. This could perhaps speak to advanced motor functions in the hands of ''A. afarensis'' and competency at precision tasks compared to non-human apes, possibly implicated in stone tool use or production.<ref>{{cite journal|first=M. R.|last=Meyer|year=2015|title=The Spinal Cord in Hominin Evolution|journal=eLS|doi=10.1002/9780470015902.a0027058|url=https://www.researchgate.net/publication/306232081|pages=1–6|isbn=9780470015902}}</ref><ref name=Haile2015/>{{rp|63–111}} However, this could have been involved in head stability or posture rather than dexterity. A.L. 333-101 and A.L. 333-106 lack evidence of this feature. The neck vertebrae of KDS-VP-1/1 indicate that the [[nuchal ligament]], which stabilises the head while distance running in humans and other cursorial creatures, was either not well developed or absent.<ref name=Haile2015/>{{rp|92–95}} KSD-VP-1/1, preserving (among other skeletal elements) six rib fragments, indicates that ''A. afarensis'' had a bell-shaped [[ribcage]] instead of the barrel shaped ribcage exhibited in modern humans. Nonetheless, the constriction at the upper ribcage was not so marked as exhibited in non-human great apes and was quite similar to humans.<ref name=Haile2015/>{{rp|143–153}} Originally, the [[vertebral centra]] preserved in Lucy were interpreted as being the [[thoracic vertebrae|T]]6, T8, T10, T11 and [[lumbar vertebrae|L]]3, but a 2015 study instead interpreted them as being T6, T7, T9, T10 and L3.<ref>{{cite journal|first1=M. R.|last1=Meyer|first2=S. A.|last2=Williams|first3=M. P.|last3=Smith|first4=G. J.|last4=Sawyer|year=2015|title=Lucy's back: Reassessment of fossils associated with the A.L. 288-1 vertebral column|journal=Journal of Human Evolution|volume=84|pages=174–180|doi=10.1016/j.jhevol.2015.05.007|pmid=26058822|bibcode=2015JHumE..85..174M |s2cid=10410978 }}</ref> DIK-1-1 shows that australopithecines had twelve thoracic vertebrae like modern humans instead of thirteen like non-human apes.<ref>{{cite journal|first1=C. V.|last1=Ward|first2=T. K.|last2=Nalley|first3=F.|last3=Spoor|first4=P.|last4=Tafforeau|first5=Z.|last5=Alemseged|year=2017|title=Thoracic Vertebral Count and Thoracolumbar Transition in ''Australopithecus afarensis''|journal=Proceedings of the National Academy of Sciences|volume=114|issue=23|pages=6000–6004|doi=10.1073/pnas.1702229114|pmc=5468642|pmid=28533391|bibcode=2017PNAS..114.6000W |doi-access=free}}</ref> Like humans, australopiths likely had five lumbar vertebrae, and this series was likely long and flexible in contrast to the short and inflexible non-human great ape lumbar series.<ref name=Haile2015>{{cite book|first1=Y.|last1=Haile-Selassie|author1-link=Yohannes Haile-Selassie|first2=D. F.|last2=Su|year=2015|title=The Postcranial Anatomy of Australopithecus afarensis: New Insights from KSD-VP-1/1|series=Vertebrate Paleobiology and Paleoanthropology|publisher=Springer|doi=10.1007/978-94-017-7429-1|isbn=978-94-017-7429-1|s2cid=133164058}}</ref>{{rp|143–153}}