On the Making of Man by Gregory of Nyssa — Read

For I think that from this beginning all our passions issue as from a spring, and pour their flood over man's life; and an evidence of my words is the kinship of passions which appears alike in ourselves and in the brutes; for it is not allowable to ascribe the first beginnings of our constitutional liability to passion to that human nature which was fashioned in the Divine likeness; but as brute life first entered into the world, and man, for the reason already mentioned, took something of their nature (I mean the mode of generation), he accordingly took at the same time a share of the other attributes contemplated in that nature; for the likeness of man to God is not found in anger, nor is pleasure a mark of the superior nature; cowardice also, and boldness, and the desire of gain, and the dislike of loss, and all the like, are far removed from that stamp which indicates Divinity.

These attributes, then, human nature took to itself from the side of the brutes; for those qualities with which brute life was armed for self-preservation, when transferred to human life, became passions; for the carnivorous animals are preserved by their anger, and those which breed largely by their love of pleasure; cowardice preserves the weak, fear that which is easily taken by more powerful animals, and greediness those of great bulk; and to miss anything that tends to pleasure is for the brutes a matter of pain. All these and the like affections entered man's composition by reason of the animal mode of generation.