Huxley recognized that unlike the earlier transmutational ideas of Jean-Baptiste Lamarck and Vestiges of the Natural History of Creation, Darwin's theory provided a mechanism for evolution without supernatural involvement, even if Huxley himself was not completely convinced that natural selection was the key evolutionary mechanism.
Huxley recoñeceu que, a diferenza das anteriores ideas sobre transmutación de Jean-Baptiste Lamarck e Vestiges of the Natural History of Creation, a teoría de Darwin proporcionaba un mecanismo para a evolución sen implicación sobrenatural, mesmo se o propio Huxley non estaba completamente convencido de que a selección natural era o mecanismo evolutivo clave.