“The very port and gait of a swan, or turkey, or peacock show the high idea he has entertain'd of himself; and his contempt of all others. This is the more remarkable, that in the two last species of animals, the pride always attends the beauty, and is discover'd in the male only. The vanity and emulation of nightingales in singing have been commonly remark'd […] All these are evident proofs, that pride and humility are not merely human passions, but extend themselves over the whole animal creation.”

Source: A Funeral for the Eyes of Fire (1975), Chapter 14, “Denouement: Ascent to the Acropolis” (p. 265)

The Devil's Notebook (1992)

"An Essay on Charity, and Charity-Schools", p. 294
The Fable of the Bees (1714)

Source: The Ape that Thought It Was a Peacock: Does Evolutionary Psychology Exaggerate Human Sex Differences? (2013), p. 147

Part 2, Section 12
A Treatise of Human Nature (1739-40), Book 2: Of the passions

Source: Vestiges of the Natural History of Creation (1844), p. 192
Context: While the external forms of all these various animals are so different, it is very remarkable that the whole are, after all, variations of a fundamental plan, which can be traced as a basis throughout the whole, the variations being merely modifications of that plan to suit the particular conditions in which each particular animal has been designed to live. Starting from the primeval germ, which, as we have seen, is the representative of a particular order of full-grown animals, we find all others to be merely advances from that type, with the extension of endowments and modification of forms which are required in each particular case; each form, also, retaining a strong affinity to that which precedes it, and tending to impress its own features on that which succeeds.

Did Adam have a Bellybutton?: And other tough questions about the Bible (2000)

Source Book in Ancient Philosophy (1907), The Golden Sayings of Democritus