I believe that animals have descended from at most only four or five progenitors, and plants from an equal or lesser number.

There is no fundamental difference between man and animals in their ability to feel pleasure and pain, happiness, and misery.

Man selects only for his own good: Nature only for that of the being which she tends.

There is continuity between humans and other animals in their emotional lives; there are transitional stages among species, not large gaps; and the differences among many animals are differences in degree rather than in kind

I do not believe, as we shall presently see, that all our dogs have descended from any one wild species; but, in the case of some other domestic races, there is presumptive, or even strong, evidence in favour of this view.

The great variability of all the external differences between the races of man, likewise indicates that they cannot be of much importance; for if important, they would long ago have been either fixed and preserved, or eliminated.