No one says that if it is natural it is also morally good. And the pear tree (not spelled "pair") is totally indifferent to you. If you were starving it would have no qualms about not producing fruit one season. Nature is quite beautiful and wondrous but virtue ( or a lack of) is our alone. If you find no room for Darwin, who you have not refuted with you "pair" tree, you do not understand nature.