PRINCIPAL COMPONENTS ANALYSIS OF MASS EXTINCTIONS USING THE PALEOBIOLOGY DATABASE

Mass extinction events are one of the most studied topics in paleontology. Throughout Earth’s history, paleontologists have identified five major mass extinctions, collectively known as the “Big Five.” The Big Five mass extinctions include the Ordovician-Silurian extinction, the Late Devonian extinction, the Permian-Triassic, the Triassic-Jurassic, and the Cretaceous-Paleogene extinction events. These mass extinctions have greatly influenced the evolutionary history of life on Earth. This study examines which organisms were susceptible to extinction and which taxa flourished following an extinction. We used the statistical procedure known as principal components analysis (PCA). This procedure transforms a number of (possibly) correlated variables into a smaller number of uncorrelated variables called principal components. The raw data for this research was retrieved from the Paleobiology Database, which contains information on origin and extinction of many taxa at any time period. The raw data were normalized and inserted into the statistical software PAST. The initial phase of research analyzed organisms throughout the Phanerozoic to determine the best base taxon (phylum, class, or order) and temporal resolution to analyze the “Big Five.” Class-level analysis produced the clearest results, and stage-level resolution produced the most detailed findings. Following this phase, research focused on a series of trials with different groups of taxa, different focus on taxa that went extinct, that survived, or that originated, and different time spans. Initial results align with previous work on extinction and broad faunal groups, which suggests some value to the technique. Further work suggests connections across taxa, some of which have easy explanations related to habitat, lifestyle, and global events, but others of which are unexpected. Comparison of taxa found during each mass extinction reveals linkages that persist at other times, such as a connection between many arthropod taxa and some brachiopods.