title: Cortical structure of hallucal metatarsals and locomotor adaptations in hominoids.
abstract: Diaphyseal morphology of long bones, in part, reflects in vivo loads experienced during the lifetime of an individual. The first metatarsal, as a cornerstone structure of the foot, presumably expresses diaphyseal morphology that reflects loading history of the foot during stance phase of gait. Human feet differ substantially from those of other apes in terms of loading histories when comparing the path of the center of pressure during stance phase, which reflects different weight transfer mechanisms. Here we use a novel approach for quantifying continuous thickness and cross-sectional geometric properties of long bones in order to test explicit hypotheses about loading histories and diaphyseal structure of adult chimpanzee, gorilla, and human first metatarsals. For each hallucal metatarsal, 17 cross sections were extracted at regularly-spaced intervals (2.5% length) between 25% and 65% length. Cortical thickness in cross sections was measured in one degree radially-arranged increments, while second moments of area were measured about neutral axes also in one degree radially-arranged increments. Standardized thicknesses and second moments of area were visualized using false color maps, while penalized discriminant analyses were used to evaluate quantitative species differences. Humans systematically exhibit the thinnest diaphyseal cortices, yet the greatest diaphyseal rigidities, particularly in dorsoplantar regions. Shifts in orientation of maximum second moments of area along the diaphysis also distinguish human hallucal metatarsals from those of chimpanzees and gorillas. Diaphyseal structure reflects different loading regimes, often in predictable ways, with human versus non-human differences probably resulting both from the use of arboreal substrates by non-human apes and by differing spatial relationships between hallux position and orientation of the substrate reaction resultant during stance. The novel morphological approach employed in this study offers the potential for transformative insights into form-function relationships in additional long bones, including those of extinct organisms (e.g., fossils).
authors: Evolutionary Studies Institute, University of the Witwatersrand, Wits, South Africa; Department of Geology and Palaeontology, Georgian National Museum, Tbilisi, Georgia.
authors: Tea
authors: T
authors: Jashashvili
authors: School of Statistics and Actuarial Science, University of the Witwatersrand, Wits, South Africa.
authors: Mark R
authors: MR
authors: Dowdeswell
authors: Institut des Sciences de l'Evolution de Montpellier-UMR 5554, Montpellier, France.
authors: Renaud
authors: R
authors: Lebrun
authors: Evolutionary Studies Institute, University of the Witwatersrand, Wits, South Africa; Department of Anthropology, Indiana University, Bloomington, Indiana, United States of America.
authors: Kristian J
authors: KJ
authors: Carlson
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D016002:Discriminant Analysis; D006214:Hallux / Q000033:anatomy & histology*; D015186:Hominidae / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D008124:Locomotion; D008682:Metatarsal Bones / Q000033:anatomy & histology*
references: J Bone Joint Surg Am. 1999 Sep;81(9):1236-44
references: 10505520
references: J Hum Evol. 2000 Feb;38(2):269-90
references: 10656779
references: J Hum Evol. 2000 Sep;39(3):297-325
references: 10964531
references: J Biomech. 2002 May;35(5):621-8
references: 11955501
references: Am J Phys Anthropol. 2002 Dec;119(4):305-42
references: 12448016
references: Am J Phys Anthropol. 2003 Apr;120(4):373-83
references: 12627532
references: J Anat. 1954 Jan;88(1):25-30
references: 13129168
references: Nature. 1964 Mar 7;201:969-70
references: 14191606
references: Am J Phys Anthropol. 2004 Feb;123(2):156-71
references: 14730649
references: Am J Phys Anthropol. 2005 Jul;127(3):312-34
references: 15584067
references: Am J Phys Anthropol. 2004;Suppl 39:63-99
references: 15605390
references: J Anat. 2005 May;206(5):453-76
references: 15857366
references: Bone. 2005 Aug;37(2):253-60
references: 15963776
references: J Hum Evol. 2005 Dec;49(6):743-61
references: 16219337
references: Am J Phys Anthropol. 2006 Apr;129(4):499-511
references: 16331658
references: J Hum Evol. 2006 Apr;50(4):394-404
references: 16376413
references: Am J Phys Anthropol. 2006 Apr;129(4):484-98
references: 16425178
references: J Anat. 1935 Oct;70(Pt 1):56-67
references: 17104575
references: Am J Phys Anthropol. 2007 May;133(1):717-22
references: 17330893
references: Am J Phys Anthropol. 1991 Nov;86(3):397-413
references: 1746645
references: J Exp Biol. 2007 Sep;210(Pt 17):3117-25
references: 17704086
references: J Hum Evol. 2007 Dec;53(6):678-90
references: 17761213
references: Am J Phys Anthropol. 1991 Dec;86(4):537-47
references: 1776660
references: Gait Posture. 2008 Jul;28(1):93-100
references: 18096389
references: Homo. 2008;59(1):27-40
references: 18234199
references: J Exp Biol. 2009 Mar;212(Pt 5):713-21
references: 19218523
references: Am J Phys Anthropol. 2009 Sep;140(1):149-59
references: 19358289
references: Am J Phys Anthropol. 2009 Sep;140(1):160-72
references: 19358297
references: Am J Phys Anthropol. 2009 Oct;140(2):324-35
references: 19382178
references: Nature. 2009 May 7;459(7243):81-4
references: 19424155
references: J Exp Biol. 2009 Aug;212(Pt 15):2491-9
references: 19617443
references: Am J Phys Anthropol. 2010 Feb;141(2):245-58
references: 19672845
references: Philos Trans A Math Phys Eng Sci. 2009 Nov 13;367(1906):4237-53
references: 19805443
references: Science. 2009 Oct 2;326(5949):72e1-8
references: 19810198
references: Int J Primatol. 2008 Dec;29(6):1401-1420
references: 19816545
references: Am J Phys Anthropol. 2010 Jun;142(2):180-93
references: 19918985
references: Am J Phys Anthropol. 2010 Jun;142(2):328-34
references: 20229503
references: J Hum Evol. 2010 Dec;59(6):608-19
references: 20851457
references: Anat Rec (Hoboken). 2011 Apr;294(4):589-609
references: 21328564
references: Anat Rec (Hoboken). 2011 Sep;294(9):1433-45
references: 21809454
references: Science. 2011 Sep 9;333(6048):1417-20
references: 21903807
references: PLoS One. 2012;7(7):e41980
references: 22848680
references: J Hum Evol. 2012 Nov;63(5):741-9
references: 23036460
references: Proc Natl Acad Sci U S A. 2013 Jan 22;110(4):1237-42
references: 23277565
references: Am J Phys Anthropol. 1990 Jun;82(2):125-33
references: 2360609
references: Hum Biol. 2013 Feb-Jun;85(1-3):309-28
references: 24297231
references: J Hum Evol. 2014 Jun;71:105-18
references: 24630525
references: PLoS One. 2014 Jul 11;9(7):e102074
references: 25013970
references: Am J Phys Anthropol. 1989 Jun;79(2):225-34
references: 2742005
references: Nature. 1987 Jan 8-14;325(7000):147-9
references: 3808070
references: Folia Primatol (Basel). 1985;45(2):61-75
references: 4093079
references: Am J Phys Anthropol. 1972 Jul;37(1):93-5
references: 5039742
references: J Anat. 1979 Aug;129(Pt 1):165-76
references: 511760
references: Am J Phys Anthropol. 1983 Mar;60(3):279-317
references: 6405621
references: Foot Ankle. 1983 May-Jun;3(6):365-76
references: 6409715
references: J Anat. 1980 Sep;131(Pt 2):275-98
references: 6780500
references: J Bone Joint Surg Am. 1995 Jul;77(7):1050-7
references: 7608227
references: J Orthop Sports Phys Ther. 1995 Jun;21(6):306-16
references: 7655474
references: J Hum Evol. 1997 Jun;32(6):523-59
references: 9210017
references: J Bone Miner Res. 1997 Oct;12(10):1539-46
references: 9333113
references: Am J Phys Anthropol. 1976 May;44(3):489-505
references: 937526
references: Am J Phys Anthropol. 1998 Jun;106(2):157-67
references: 9637181