Certain Quote by Alfred Russel Wallace

“All organisms vary. It is in the highest degree improbable that any given variety should have exactly the same relations to surrounding conditions as…

— Thomas Henry Huxley

As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence,…

— Charles Darwin

Hereafter we shall be compelled to acknowledge that the only distinction between species and well-marked varieties is, that the latter are known, or believed…

— Charles Darwin

Splitting and gradual divergence of genera is exemplified very well and in a large variety of organisms.

— George Gaylord Simpson

If we look round the world, there seem to be not above six distinct varieties in the human species, each of which is strongly…

— Oliver Goldsmith

Transitional forms are generally lacking at the species level, but they are abundant between larger groups.

— Stephen Jay Gould

It is now firmly established that ontogeny does not repeat phylogeny

— George Gaylord Simpson

I have called this principle, by which each slight variation, if useful, is preserved, by the term of Natural Selection.

— Charles Darwin

But just in proportion as this process of extermination has acted on an enormous scale, so must the number of intermediate varieties, which have…

— Charles Darwin

The evolution of cultures appears to follow the pattern of the evolution of species. The many different forms of culture which arise correspond to…

— B. F. Skinner

Why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms.

— Charles Darwin

In general, the more one augments the number of divisions of the productions of nature, the more one approaches the truth, since in nature…

— Georges-Louis Leclerc, Comte de Buffon