The more I study Nature, the more I become impressed with ever-increasing force that the contrivances and beautiful adaptations slowly acquired through each part, occasionally varying in a slight degree, but in many ways, with the preservation of those variations which were beneficial to the organism under complex and ever-varying conditions of life, transcend in an incomparable manner the contrivances and adaptations which the most fertile imagination of man could invent.

The main conclusion here arrived at ... is that man is descended from some less highly organized form.

Light will be thrown on the origin of man and his history.

I was a young man with uninformed ideas. I threw out queries, suggestions, wondering all the time over everything; and to my astonishment the ideas took like wildfire. People made a religion of them.

If man had not been his own classifier, he would never have thought of founding a separate order for his own reception.

The plow is one of the most ancient and most valuable of man's inventions; but long before he existed the land was in fact regularly plowed, and still continues to be thus plowed by earthworms. It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.

The normal food of man is vegetable.

Sympathy beyond the confines of man, that is, humanity to the lower animals, seems to be one of the latest moral acquisitions.

But then with me the horrid doubt always arises whether the convictions of man's mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey's mind, if there are any convictions in such a mind?