Book Summary:
Multicellular animals first appear in the fossil record during the Late Neoproterozoic, and show a considerable proliferation during the Cambrian, i.e., the “Cambrian Explosion.” While the fossil record implies an origin for most animal phyla during this time, molecular clocks have consistently suggested a much deeper history of animals, extending back approximately 1000 million years before present (Ma). The disparity between fossil and molecular times is confounded by an incomplete understanding of the relationships among different animal phyla, and of the relatedness of animals to the other multicellular eukaryotes (fungi and plants). This thesis research uses genomic data to reconstruct phylogenetic relationships and estimate divergence times among animals and between animals and other eukaryote groups. Different molecular clock methods, such as global and local clocks, are utilized and the consistency of divergence time estimates is examined. A new technique is also proposed for the assembly of orthologous protein datasets from complete eukaryote genomes. In general, this thesis establishes a more robust timeline for eukaryotic evolution during the Proterozoic Eon of Earth's history (2500–545 Ma), allowing correlations between biological and geologic events to be made. |