This paper challenges the prevailing monophyletic theory of evolution—the idea that all life shares a single common ancestor—by rigorously testing its compatibility with empirical data. The author employs five key tests: protein phylogenies, structural and numerical mutations, gene mutations, chromosome number and DNA quantity, and the fossil record. He argues that none of these tests provide sufficient empirical support for the monophyletic hypothesis, finding instead that the data suggest "fixity of kinds," with significant breeding gaps between major groups of organisms. Ultimately, the paper advocates for a polyphyletic interpretation of life's history, calling for a more balanced presentation of both monophyletic and polyphyletic viewpoints in scientific literature and education.