Doctoral Dissertation Improvement: Morphological Integration and Evolution of the Hominoid Vertebral Column

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

The living apes share a number of derived skeletal morphologies of the trunk and limbs, features that distinguish them from many other primates and mammals in general. Traditionally, many of these morphologies have been associated with the use of upright trunk posture. Whether this fundamental shift occurred once in the common ancestor of all apes or whether it evolved independently in multiple lineages remains contentious. Parallelism, independent evolution through identical genetic or developmental pathways, is complicated and notoriously difficult to detect. The problem of parallelism in understanding locomotor evolution amongst apes is profound because it underlies the understanding of when major changes in locomotion occurred and which behaviors were the necessary precursors to human bipedalism. This problem is also encountered in the fossil record where certain fossils confound the understanding of hominoid evolution and the number of times that upright trunk posture has evolved. The vertebral column plays a central role in posture and locomotion and its orientation characterizes the main types of body plans among mammals. This study seeks to test the hypothesis of parallel evolution by employing quantitative evolutionary methods to identify patterns of integration and potential constraints on evolvable morphologies. These methods will be used to resolve longstanding controversies concerning the number of times that orthogrady has evolved in living and fossil hominoids. The intellectual merit of this study includes its contribution toward a synthesis of models and theories in the fields of evolutionary and developmental biology. This work is part of a larger research project that aims to quantify patterns of morphological integration in the entire primate postcranial skeleton. Broader impacts of this work include facilitation of graduate research training for one student, and collaboration among faculty and graduate students at the University of Illinois as well as at other academic institutions.