There is a tendency in nature to the continued progression of certain classes of varieties further and further from the original type.
Alfred Russel WallaceCivilisation has ever accompanied emigration and conquest - the conflict of opinion, of religion, or of race
Alfred Russel WallaceOn the spiritual theory, man consists essentially of a spiritual nature or mind intimately associated with a spiritual body or soul, both of which are developed in and by means of a material organism
Alfred Russel WallaceMars, therefore, is not only uninhabited by intelligent beings such as Mr. Lowell postulates, but is absolutely uninhabitable.
Alfred Russel WallaceWhy do some die and some live? The answer was clearly, that on the whole the best fitted live. From the effects of disease the most healthy escaped; from enemies, the strongest, swiftest, or the most cunning; from famine, the best hunters or those with the best digestion; and so on. Then it suddenly flashed upon me that this self-acting process would necessarily improve the race, because in every generation the inferior would inevitably be killed off and the superior would remain-that is, the fittest would survive.
Alfred Russel Wallace