"For countless ages the fruit of this tree underwent the gradual changes of evolution, passing by degrees from true plant life to a combination of plant and animal. In the first stages the fruit of the tree possessed only the power of independent muscular action, while the stem remained attached to the parent plant; later a brain developed in the fruit, so that hanging there by their long stems they thought and moved as individuals.
"Then, with the development of perceptions came a comparison of them; judgments were reached and compared, and thus reason and the power to reason were born upon Barsoom.
"Ages passed. Many forms of life came and went upon the Tree of Life, but still all were attached to the parent plant by stems of varying lengths. At length the fruit tree consisted in tiny plant men, such as we now see reproduced in such huge dimensions in the Valley Dor, but still hanging to the limbs and branches of the tree by the stems which grew from the tops of their heads.