Understanding the forces that shaped the appearance and development of modern humans has been a leading goal of biological anthropology for decades. As technology has improved, our capability to investigate key questions about the factors affecting the shape of our anatomy have advanced significantly. Here, an interdisciplinary team of anthropologists and engineers will use engineering and experimental methods to examine how the shape of the skull has evolved in order to adapt to the forces associated with feeding on different types of food items. Specifically, the researchers will take a highly interdisciplinary approach to examining whether the skulls of these early humans were well designed to crack open and chew such hard, brittle objects. Dietary adaptations are thought to have been critical factors influencing the course of early human evolution, so this research project will provide valuable insights into the functional anatomy, diet, ecology and behavior of the earliest human ancestors.
With respect to intellectual merit, this project will: (a) examine the functional and evolutionary relationships between diet and skull form, (b) test a leading hypothesis explaining the evolution of the earliest humans, (c) collect and integrate multiple types of raw data critical to an understanding of feeding biomechanics, (d) develop methods for the rapid construction of engineering models that can be applied to research questions in a wide range of disciplines, (e) integrate ecological, comparative, experimental, and engineering techniques for the investigation of evolutionary questions, and (f) rapidly disseminate data, models and findings to the scientific community.
With respect to broader impacts, this study will: (a) promote interdisciplinarity, diversity and internationalism in science, (b) collect data about skull biomechanics that are relevant to dentistry and craniofacial medicine, (c) support the research of three junior investigators each in the first year of their academic appointments, (d) support female graduate students at several universities, (e) provide support to undergraduates at a university whose student body has a high proportion of minorities, (f) provide training for international students in developing nations (Brazil, Suriname), which will ultimately support the development of scientific infrastructure and institutions in those countries, (g) provide content to an exhibit focusing on human biology and evolution at the Georgia Children?s Museum, (h) using engineering models, limit the need for, or at least increase the analytical power of, future experimental studies requiring the use of live animals, (i) generate data relevant to conservation efforts by documenting the relationship between ecology and adaptation in certain primates, (j) strengthen collaborations between anthropologists and engineers in ten universities and two countries, (k) heighten awareness in the engineering community about how their methods are applicable to evolutionary questions.
The australopiths are extinct, early human ancestors who lived in Africa between about 4.2 and 1.4 million years ago. They exhibit a number of distinct skeletal features in their faces that are thought to be adaptations for feeding on very hard or very tough foods, suggesting that diet was a major factor in shaping aspects of early human evolution. However, it has been very difficult to evaluate hypotheses about the function of the features because the facial skeleton has a very complex geometry, thereby confounding attempts to formulate and test biomechanical hypotheses. We attempted to solve this problem by using finite element analysis, a computer-based modeling technique that examines how objects of complex design (like a skull) respond to loads (such as the forces involved during feeding). We tested two fundamental hypotheses. First, we tested whether or not a relationship exists between the material properties (i.e., hardness, toughness, stiffness) of foods and variation in the mechanical strains in the facial skeleton that are caused by eating those foods. Second, we tested whether or not the distinctive facial features in australopiths are adaptations for eating hard foods. With respect to the first hypothesis, we found results suggesting that food material properties, per se, are not the most important factor driving strain patterns in the face, but rather that the manner in which were consumed may have a much more important impact. This suggests that researchers should focus attention on feeding behaviors rather than simply the hardness or toughness of foods. With respect to the second hypothesis, we found results consistent with the hypothesis that some australopith facial features are adaptions for feeding on hard foods. However, we also found some unexpected results. Primarily, we found that the most heavily built australopiths did not have faces that we demonstrably stronger than those with more lightly built faces. This suggests the key variable influencing the evolution in facial form in these species is not skeletal strength but rather the ability to produce ever increasing forces during biting. This result suggests that researchers will need to re-think the conventional wisdom regarding the biomechanics of australopithecine facial structure.
