Cranial base flexion and H. erectus skulls.

Abstract

Our hypothesis about the role of cranial base flexion in the evolution of modern human cranial form is mischaracterized by Ann Gibbons in her article “Java skull offers new view of Homo erectus (News of the Week, 28 Feb., p. 1293). The highly flexed cranial base angle of the new H. erectus skull from Java, Sm 4, is extremely interesting but would not be expected to have a simple relationship to aspects of overall cranial shape such as neurocranial globularity (the three-dimensional roundedness of the cranial vault) because of substantial interactions that occur between the cranial base and both the brain and the face ([1][1]). Indeed, other hominid species such as Paranthropus boisei are known to have flexed cranial bases without globular skulls or retracted faces ([2][2]). Our study ([3][3]), which focused solely on the evolutionary transformation of modern humans from archaic Homo (and thus did not include any H. erectus skulls), proposed that increased cranial base flexion in combination with a large brain and a smaller face contributes to facial retraction and neurocranial globularity. So far, we know of no archaic Homo crania with a large brain and a flexed cranial base in the range of modern H. sapiens. Sm 4 has a flexed cranial base (141°) but also has a small brain (1006 cm3) and a presumably large face. As midsagittal flexion alone does not play a decisive role in either facial retraction, facial projection, or neurocranial globularity, we would not expect Sm 4 to have either a globular neurocranium or a retracted face. Contrary to what was reported, our hypothesis would require modification only if additional H. erectus skulls were found with very flexed cranial bases combined with large brains and small faces, but which did not have globular cranial vaults and retracted faces. 1. [↵][4]1. D. E. Lieberman, 2. C. F. Ross, 3. M. J. Ravosa , Yrbk. Phys. Anthropol. 43, 117 (2000). [OpenUrl][5] 2. [↵][6]1. F. Spoor , S. Afr. J. Sci. 93, 182 (1997). [OpenUrl][7][GeoRef][8][Web of Science][9] 3. [↵][10]1. D. E. Lieberman, 2. B. M. McBratney, 3. G. E. Krovitz , Proc. Natl. Acad. Sci. U.S.A. 99, 1134 (2002). [OpenUrl][11][Abstract/FREE Full Text][12] [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #xref-ref-1-1 View reference 1 in text [5]: {openurl}?query=rft.jtitle%253DYrbk.%2BPhys.%2BAnthropol.%26rft.volume%253D43%26rft.spage%253D117%26rft.atitle%253DYRBK%2BPHYS%2BANTHROPOL%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [6]: #xref-ref-2-1 View reference 2 in text [7]: {openurl}?query=rft.jtitle%253DSouth%2BAfrican%2BJournal%2Bof%2BScience%26rft.stitle%253DSouth%2BAfrican%2BJournal%2Bof%2BScience%26rft.volume%253D93%26rft.issue%253D4%26rft.spage%253D182%26rft.epage%253D186%26rft.atitle%253DBasicranial%2Barchitecture%2Band%2Brelative%2Bbrain%2Bsize%2Bof%2BSts%2B5%2B%2528Australopithecus%2Bafricanus%2529%2Band%2Bother%2BPlio-Pleistocene%2Bhominids%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [8]: /lookup/external-ref?access_num=1998006784&link_type=GEOREF [9]: /lookup/external-ref?access_num=A1997XM63800028&link_type=ISI [10]: #xref-ref-3-1 View reference 3 in text [11]: {openurl}?query=rft.jtitle%253DProc.%2BNatl.%2BAcad.%2BSci.%2BU.S.A.%26rft_id%253Dinfo%253Adoi%252F10.1073%252Fpnas.022440799%26rft_id%253Dinfo%253Apmid%252F11805284%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [12]: /lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6NDoicG5hcyI7czo1OiJyZXNpZCI7czo5OiI5OS8zLzExMzQiO3M6NDoiYXRvbSI7czoyNDoiL3NjaS8zMDAvNTYxNy8yNDkuMy5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=