Doctoral Dissertation Research: The shape of hands and feet and the transition to upright walking

Duke University, Durham NC

Investigators

Abstract

Researchers have long hypothesized that the transition to upright walking on two legs (bipedalism) in humans was facilitated in our distant, non-primate ancestors by an increased reliance on the hind limb while walking on four legs. As a pivotal part of our evolutionary trajectory, it is proposed that once our ancestors’ hands were freed from involvement in walking, they were able to be used for other purposes such as tool use, grooming, and carrying. Previous research on the transition to upright walking in human ancestors has largely focused on non-human primates. To better understand whether the relationship between reliance on hind limbs while walking on four legs and the emergence of bipedalism is unique to human evolution, this doctoral dissertation research project casts a broad comparative net and includes a comparison between primates and carnivores. This project offers opportunities for undergraduate students to gain exposure to STEM-discipline focused ideas and research questions, and to receive transferable technical training and experience. This project tests the hypothesis that the development of a dominant limb is associated with morphological and functional diversification of the non-dominant limb. This project tests this and related hypotheses in three ways: (1) testing if increased reliance on the hind limb allows for diversification of the forelimb by tracking co-variation of hand and foot bones across an expansive sample of extant primate taxa; (2) assessing the effect of limb dominance on functional diversity in an independent mammalian clade (Carnivora) that is thought not to have been characterized by hind limb dominance during its early evolution; and (3) conducting a large-scale comparison of primate and mammalian carnivoran hand and foot bones to track rates of shape variation across both orders. Understanding the ways that the bones of the hands and feet of these groups have evolved helps to elucidate a better understanding of the underlying processes that took place in primates millions of years ago shaping the trajectory of modern human evolution. The broad perspective used in this study is innovative and informative for better understanding of the evolution of bipedalism in humans. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.