Ledogar publishes on craniofacial feeding biomechanics

Dr. Justin Ledogar, Assistant Professor in East Tennessee State University’s College of Public Health, is lead author of an article recently published in the journal Proceedings of the Royal Society B: Biological Sciences. The article, “Mechanical compensation in the evolution of the early hominin feeding apparatus,” aims to better understand evolutionary trends in craniofacial strength and feeding biomechanics in australopiths. Co-authors include faculty from Washington University in St. Louis and the University of Chicago.

The australopiths, a group of extinct hominins from the Plio-Pleistocene of Africa, are characterized by derived traits in their crania that are hypothesized to strengthen the facial skeleton against feeding loads and increase the efficiency of bite force production. Within this group, the crania of “robust” australopiths are further thought to be stronger and more efficient than those of “gracile” australopiths.

The study uses a computer-aided engineering technique called finite element analysis to simulate biting mechanics in an early “gracile” australopith species called Australopithecus afarensis, the same species that includes the famous “Lucy” fossils. The results were then compared to a sample of previously-analyzed species, including more recent “gracile” australopiths, a “robust” australopith, and a sample of modern chimpanzees.

Results of the comparisons show that some “gracile” australopith crania are as strong as that of a “robust” australopith, and the strength of “gracile” australopith crania overlaps substantially with that of chimpanzee crania. The authors conclude that the evolution of cranial traits that increased the efficiency of bite force production in australopiths may have simultaneously weakened the face, leading to the compensatory evolution of additional traits that reinforced the facial skeleton. The evolution of facial form in early hominins can therefore be thought of as an interplay between the need to increase the efficiency of bite force production and the need to maintain the structural integrity of the face.