This chapter examines how scientific interest in Charles Darwin's evolutionary trees declined and then increased in the twentieth century. As the nineteenth century drew to a close, the reality of evolution became firmly established among scientists. Darwin deserves credit for the overused idea of a paradigm shift—evolution was a scientific “fact,” but not so for his theory of natural selection. Intellectual retreat from Darwin's natural selection can be attributed in part to his failure to provide an adequate hypothesis of inheritance or the source of variation on which his natural selection was to act. This chapter explores how the still emerging field of vertebrate paleontology and the ideas of evolutionary mechanisms that accompanied them affected visual representations of evolution in trees. In particular, it looks at the so-called bone wars between Edward Drinker Cope and Othniel Charles Marsh in the United States, Henry Fairfield Osborn's aristogenetic trees, and the rise of neocreationism. It also considers the contributions of William King Gregory, Alfred Sherwood Romer, and George Gaylord Simpson in visualizing biological order.