Biologically, of course, human beings are animals. The definition of human uses the term mammal; the definition of mammal uses vertebrate; the definition of vertebrate finally identifies the organism as an “animal.” (Sometimes definitions are like Russian dolls, uncovering ever-more specific classification with each successive cross-reference.) Outside of this basic definition, the use of the word animal as a metaphor referring to people and their characters or characteristics has a long history in the language. This use traces back to the time of Shakespeare, and, indeed, Shakespeare’s use of animal shows the range its use. Sometimes, people are identified as occupying the highest position in the hierarchy of the genus:
What a piece of work is a man! how noble in reason! how infinite in
faculties! in form and moving how express and admirable! in
action how like an angel! in apprehension how like a god!
the beauty of the world, the paragon of animals!
— Shakespeare, Hamlet, II, 2
Sometimes, people are identified as not superior to other animals but just one species among others:
Is man no more than this? Consider him well.
Thou ow'st the worm no silk, the beast
no hide, the sheep no wool, the cat no perfume. Ha! Here's three
on's are sophisticated! Thou art the thing itself;
unaccommodated man is no more but such a poor, bare, forked
animal as thou art.
— Shakespeare, King Lear,III, 4
And at other times, animal is used to indicate that a person is somehow less than human, usually in intelligence:
Sir, he hath never fed of the dainties that are bred
in a book; he hath not eat paper, as it were; he
hath not drunk ink: his intellect is not
replenished; he is only an animal, only sensible in
the duller parts
— Shakespeare, Love's Labour's Lost, IV, 2
Samuel Johnson’s dictionary of 1755 included this figurative meaning of animal (and Noah Webster included it in his dictionary of 1828):
By way of contempt, we say of a stupid man, that his is a stupid animal.
A finer distinction has subsequently been made by dictionaries, as shown in this definition from the 1934 edition of Merriam-Webster’s Unabridged:
: Pertaining to the sentient part of a creature, as distinguished from the intellectual, rational, or spiritual. “Our animal appetites and daily wants.” Wordsworth
This use was embodied in the character of the Muppet drummer named Animal.
Animal anthropomorphism of a non-derogatory sort goes back at least to political animal, which has been in the language since the early 1700s. A more neutral reference to the division between the intellectual and physical side of human beings is the term animal magnetism, which also dates to the 1700s.
Let’s take a look at some of those colorful words that can turn humdrum writers into party animals. (Party animal, by the way, was first used by Bill Murray in a Saturday Night Live sketch from 1977, according to the Oxford English Dictionary.)