DOI: 10.5061/dryad.j0zpc86k6
title: Finite element models presented from: Bite force production and the origin of Homo

description: The divergence of Homo from gracile australopiths has been
 described as a trend of decreasing dentognathic size and robusticity,
 precipitated by stone tool use and/or a shift to softer foods, including
 meat. Yet, mechanical evidence supporting this narrative is sparse, and
 isotopic and archaeological data have led to the suggestion that a shift
 away from a gracile australopith-like diet would not have occurred in the
 most basal members of Homo but rather only with the appearance of H.
 erectus, implying that the origin of our genus is not rooted in dietary
 change. Here, we provide mechanical evidence that H. habilis exhibits an
 australopith-like pattern of facial strain during biting but, unlike most
 australopiths, was not suited for a diet that required forceful processing
 by the molar teeth. H. habilis was at elevated risk of distractive jaw
 joint forces during those bites, constraining muscle recruitment so as to
 avoid generating uncomfortable/dangerous levels of tension in the joint.
 Modern humans have similar limitations. This suggests that selection on
 skeletal traits favouring forceful postcanine processing wereas relaxed by
 the earliest stages in the evolution of our genus, implying that dietary
 or food processing changes played an important role in the emergence of
 Homo. The divergence of Homo from gracile australopiths has been
 described as a trend of decreasing dentognathic size and robusticity,
 precipitated by stone tool use and/or a shift to softer foods, including
 meat. Yet, mechanical evidence supporting this narrative is sparse, and
 isotopic and archaeological data have led to the suggestion that a shift
 away from a gracile australopith-like diet would not have occurred in the
 most basal members of Homo but rather only with the appearance of H.
 erectus, implying that the origin of our genus is not rooted in dietary
 change. Here, we provide mechanical evidence that H. habilis exhibits an
 australopith-like pattern of facial strain during biting but, unlike most
 australopiths, was not suited for a diet that required forceful processing
 by the molar teeth. H. habilis was at elevated risk of distractive jaw
 joint forces during those bites, constraining muscle recruitment so as to
 avoid generating uncomfortable/dangerous levels of tension in the joint.
 Modern humans have similar limitations. This suggests that selection on
 skeletal traits favouring forceful postcanine processing wereas relaxed by
 the earliest stages in the evolution of our genus, implying that dietary
 or food processing changes played an important role in the emergence of
 Homo.
description: # Finite element models presented in: Bite force production and the origin
 of Homo by Ledogar et al. Dataset DOI:
 [10.5061/dryad.j0zpc86k6](10.5061/dryad.j0zpc86k6) ## Description of the
 data and file structure README file accompanying the Finite Element Models
 presented in “BITE FORCE PRODUCTION AND THE ORIGIN OF *HOMO*” by Ledogar
 et al. Cranial finite element models are provided for four fossil hominin
 specimens (KNM-ER 1813, AL 444-2, MH1, OH5, Sts 5), six specimens of *Pan
 troglodytes* (PC1-, PC1+, PC2-, PC2+, PC3-, PC3+), and seven specimens of
 modern *Homo sapiens* (BERG, GRGL, KSAN1, KSAN2, MALP, TIGA, WAFR). Each
 of these 18 models has been subjected to two loading conditions, one
 simulating a maximal bite on the third premolar (P3), and one on the
 second molar (M2). For each bite case, we subjected each FEM to
 isometrically scaled muscle forces derived from a chimpanzee (*Pan
 troglodytes*) simulating a maximal bite (all muscles contracting at peak
 activity). FEMs of modern humans and *Homo habilis* were loaded a second
 time using isometrically scaled muscle forces derived from a modern human
 (*Homo sapiens*). ### Files and variables #### File:
 Ledogar\_et\_al\_FEMs.zip **Description:**  Two files have been uploaded
 for each loading condition.  One file, in .st7 format, consists of the
 finite element model. The other file, in .LSA format, consists of the
 results corresponding that loading condition. These files open in Strand7
 software. These files can be reformatted for conversion to other file
 types for use in other finite element analysis software. The names of the
 files indicate the specimen, loading condition (P3 or M2 bite), muscle
 forces (chimpanzee or human), and file type. For example, KNM-ER
 1813_P3_chimpanzee forces.st7 is the file containing the finite element
 model of specimen KNM-ER 1813 that simulates a bite on the P3 using
 isometrically scaled muscle forces derived from a chimpanzee. To view the
 results corresponding to this model, open the file in Strand7 software,
 open the results window and select KNM-ER 1813_P3_chimpanzee forces.LSA.
 Additionally, we have provided models as NASTRAN files. These files
 preserve the geometry of the models and details on loading conditions.
 They do not preserve the material properties, which as described in our
 paper change as gradients throughout the model. Additionally, results
 (.LSA) files cannot be opened when using these files outside of Strand7.
 However, the models can be imported into non-proprietary software and
 analyzed by other researchers who don’t have access to Strand7. ##
 Code/software n/a ## Access information n/a