There is no fundamental difference between man and animals in their ability to feel pleasure and pain, happiness, and misery.
Charles DarwinOn seeing the marsupials in Australia for the first time and comparing them to placental mammals: “An unbeliever . . . might exclaim 'Surely two distinct Creators must have been at work'”
Charles DarwinIt is scarcely possible to doubt that the love of man has become instinctive in the dog.
Charles DarwinThe several difficulties here discussed, namely our not finding in the successive formations infinitely numerous transitional links between the many species which now exist or have existed; the sudden manner in which whole groups of species appear in our European formations; the almost entire absence, as at present known, of fossiliferous formations beneath the Silurian strata, are all undoubtedly of the gravest nature.
Charles Darwin