With the relatively recent proliferation in the number and variety of genders that our contemporaries willingly proclaim themselves to be or belong to, a new intransitive sense of the verb identify, not yet registered by many dictionaries, seems to have emerged.
In the Wikipedia article on Transgender, for instance, we read
transgender people may identify as heterosexual, homosexual, bisexual, asexual, etc. (emphasis added).
I suspect that this usage evolved from a reflexive one. We can even see this evolution within a single article in today’s (or tomorrow’s) New York Times, “Asexual and Happy” by Kim Kaletsky:
¶15: It wasn’t until I spoke to a friend who identified herself as falling on the asexual spectrum that I realized how much the term resonated with me (emphasis added). . . .
¶26: I went on OkCupid dates with people who identified on the asexual spectrum.
(The usage of “on the X spectrum” to mean, presumably, “more or less X” is another interesting trend.)
Merriam-Webster offers only the following intransitive senses, neither applicable here:
1: to be or become the same
2: to practice psychological identification <identify with the hero of a novel>
OED offers only this last as a non-obsolete intransitive sense. But it also provides the following as a reflexive sense, which seems far closer to the intransitive sense here in question.
II.5.b. refl. To prove, reveal, or declare one’s identity.
The Free Dictionary has an idiom entry for “identify as” but only as transitive, with a direct object between the two words.
Under the verb alone, it all too briefly notes an intransitive sense as
3. To self-identify
—which seems to suggest a kind of reflexive-to-intransitive evolution.
When, where, and why did this happen for identify, and is it a common evolutionary pattern for English verbs? One other much earlier example that springs to mind is bathe, for which the OED derives the intransitive sense “to take a bath” (“c1200”) from reflexive use of an older (“a1200”) transitive sense.