Bipedalism is a hallmark of humans, and as such has been the focus of extensive paleoanthropological research. Numerous studies have shown that many of the characteristics unique to human body form can be explained as adaptations for efficient bipedal locomotion. However, there also appears to be some degree of plasticity in skeletal form as it relates to bipedalism, with aspects of knee shape in particular being a response to the biomechanical stresses of upright walking.
The peculiar dependence of knee form on juvenile locomotor behavior speaks to the value of considering the evolution of bipedalism from an ontogenetic prospective. Under the direction of Dr. Tim Weaver of UC Davis, and Dr. Zeray Alemseged of the University of Chicago, graduate student Peter Stamos is studying human, extant ape, and early hominin knee growth trajectories. Utilizing three-dimensional geometric morphometrics, the study will consider juvenile knee form, knee ontogeny, and the interplay between ontogeny and biomechanical stress in an attempt to make inferences about the locomotor behavior of early hominins.
Life history theory is concerned with the pace and ways in which an organism allocates resources to growth, development, and reproduction. The study of life history is important in paleoanthropology because the life history pattern exhibited by modern humans is unique among primates. In particular, modern humans are characterized by an extended juvenile period, large adolescent growth-spurt, and incredibly long post-reproductive life-span. These characteristics, which are typical of a “slow” life-history, are contrasted by a young weaning age and short interbirth interval in humans, characteristics more typical of animals with “fast” life-histories. Because of these unique aspects of human life histories, and the implications they have for the development of human cognition and culture, trying to decipher the evolutionary development of human life history is of paramount interest to anthropologists.
Peter Stamos' research into primate locomotor ontogeny aims to give insight into the life history patterns of our early ancestors. Namely, the research will attempt to determine when locomotor independence was achieved in young Australopithecus afarensis individuals.