the world's organisms goes back to Aristotle's biology. In his History of Animals, where he ranked animals over plants based on their ability to move and sense, and graded the animals by their reproductive mode, live birth being "higher" than laying cold eggs, and possession of blood, warm-blooded mammals and birds again being "higher" than "bloodless" invertebrates.

Aristotle's non-religious concept of higher and lower organisms was taken up by