This project investigates the evolution of the human pattern of growth and development. Unlike other primates, anatomically modern humans grow for a very long time, extending the period between birth and sexual maturation. The appearance of this distinctly human pattern of growth and development in our species' evolution, and whether or not it is shared even more widely with earlier fossil species such as Neandertals, are issues that remain controversial. In order to help resolve this problem, this project focuses on the frontal bone of the skull, and its associated browridge, as a window into changes in development. This project tests the hypothesis that major differences in frontal bone form, often used in human evolution to distinguish between different species and sexes, may actually be the result of small changes in size that manifest as themselves as significant differences in browridge shape during growth. This research helps determine whether or not modern humans are actually "scaled down" versions of Neandertals or other fossil species. A trend towards juvenilization during human evolution is expected, with modern humans following an ancestral growth pattern to a shorter endpoint.
Three-dimensional data on the browridge and frontal bone will be collected through newly-developed photometric equipment (ShapeCam). Data are taken from digital images rather than the skeletal materials themselves, increasing accuracy and volume of data while diminishing damage that may occur with traditional measurement devices. This system facilitates electronic data sharing among researchers, and aids in the preservation of fragile fossil and skeletal materials. This project will see the first significant use of the ShapeCam system in Physical Anthropology.
The broader impact of this project concerns the insights it generates on the dynamics of human growth. Understanding the evolution of prolonged human growth will help to interpret increased longevity in humans and inform evolutionary theories of aging. Identifying when and how the evolution of the human pattern of growth and development occurred also has important implications for understanding human social organizations and kinship systems. This adaptation has been related to a long period of child dependence, learning, and the acquisition of knowledge, which may have resulted in the need for humans to form stronger bonds due to intense investment in infants. In addition, a comparative understanding of growth and development has important biomedical implications and wider applications to addressing causes of variation in human growth and understanding human growth deficiencies. Graduate student training is an important component in this project.
