A rill in a barnyard and the Grand Canyon represent, in the main, stages of valley erosion that began some millions of years apart.

To put it crudely but graphically, the monkey who did not have a realistic perception of the tree branch he jumped for was soon a dead monkey-and therefore did not become one of our ancestors.

Most of the dogmatic religions have exhibited a perverse talent for taking the wrong side on the most important concepts in the material universe, from the structure of the solar system to the origin of man.

...the argument from absence of transitional types boils down to the striking fact that such types are always lacking unless they have been found.

Almost all paleontologists recognize that the discovery of a complete transition is in any case unlikely.

It remains true, as every paleontologist knows, that most new species, genera, and families, and that nearly all categories above the level of families, appear in the record suddenly and are not led up to by known, gradual completely continuous transitional sequences.

The opposition to teaching evolution is, of course, almost always given a religious reason. That may usually be its real basis, but I think it is often a mask, perhaps unconscious, for underlying anti-intellectualism or antiscientism.

The meaning that we are seeking in evolution is its meaning to us, to man. The ethics of evolution must be human ethics. It is one of the many unique qualities of man, the new sort of animal, that he is the only ethical animal. The ethical need and its fulfillment are also products of evolution, but they have been produced in man alone.

If a sect does officially insist that its structure of belief demands that evolution be false, then no compromise is possible. An honest and competent biology teacher can only conclude that the sect's beliefs are wrong and that its religion is a false one.

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

It is inherent in any definition of science that statements that cannot be checked by observation are not really saying anything or at least they are not science.

Man is the result of a purposeless and materialistic process that did not have him in mind. He was not planned. He is a state of matter, a form of life, a sort of animal, and a species of the Order Primates, akin nearly or remotely to all of life and indeed to all that is material.

Recognition of this kinship with the rest of the universe is necessary for understanding him, but his essential nature is defined by qualities found nowhere else, not by those he has in common with apes, fishes, trees, fire, or anything other than himself.