the american geologist edward hitchcock (1763–1864) published in 1840 the first tree of life based on paleontology in his "elementary geology". on the vertical axis are paleontological periods. hitchcock made a separate tree for plants (left) and animals (right). the plant and animal trees are not connected at the bottom of the chart. furthermore, each tree starts with multiple origins. however, they were not "evolutionary" trees, because hitchcock believed that a deity was the agent of change.