grammatical number - What is the true gender-neutral equivalent of "man"?

Man is a social animal.

This sentence is understandable, but has two problems:

1. The gender-neutral use of man is nowadays often seen as sexist.


2. The phrasing seems archaic.

Let’s ignore the second problem and try to fix only the first:

*Human is a social animal.

This is just wrong. But why? It’s exactly the same phrasing; the only change is that it now has a truly gender-neutral word instead of the pseudo-gender-neutral man. What’s wrong with that?

To truly render that phrase in modern English, you need to either pluralize it or recast it entirely:

Humans are social animals.
Humanity is a social species.

Somehow the “generic singular” which works with man does not work with human. Why not?

Answer

"The human being is a social animal."

(See relevant Google Ngram Viewer chart that confirms that this usage exists and seems to be more common than something like "The human is a social animal.")

"Man" in this construction just doesn't behave like a normal singular noun, so you can't substitute one. You have to use an ordinary singular noun phrase, and singular noun phrases in English usually have to include some determiner like the or a (the main exception I can think of is mass nouns like "water" or "grass"). In these kind of "generic singular" contexts, the definite article the is often used as the determiner of the singular noun.

It doesn't seem very unusual to me that the word "man" developed unique grammatical features like this. It has a very general meaning and words like this often undergo some degree of "grammaticalization". In German, "man" has become even more grammaticalized and is an indefinite pronoun. In French, the Latin noun homo "man" developed into the indefinite pronoun on, which subsequently gained a further grammatical use as a first-person plural pronoun.