A complex functional category would be : "I have a concept of a class, X, such that members of which have X-like interactions with me; have certain spatial constraints (I can not know of Xness in two places at the same time - or two distant places within a very short interval of each other.)"
My answer : either
or
Taking the latter aproach could lead in one of two directions :
But in general there's another interesesting question : "What's the difference between the concept of a function and the concept of something else? - Are there things that are NOT functional?"
If I say creature X has a concept of individual - but my only criteria is some behavioral sub-component eg. niceness (though something better would be better.), and indeed I deny an explicit representation of individuals (or the concept is-an-individual) aren't I relying on the slide between the concept of individual and the complex functional concept - the distinction between which is precisely what I seem to be interested in.
My answer : [to be continued]
For example, human surnames used to be named after their job (or function). Perhaps individuality is a thoroughly modern concept.
I don't have a lot to say about this. I've been reading a book by Alain Renaut : The Era of the Individual (http://pup.princeton.edu/titles/6042.html) which criticises Heidegger's attack on humanism and traces a history of the notion of the human subject. It's suggestive, though I'm a bit loath to argue that phylogeny recapitulates philosophy.
There's a sense in which parallels between human institutional developments, (as described by economics) and biological evolution, can be interesting analogies. They can suggest something of the ecological relevance of certain behaviours.
For example, a lack of emphasis on individual identity, as opposed to role, in cities compared to villages, may be symptomatic of a lack of repeat encounters between the same individual. And correspondingly, a species where repeat encounters are rare, may never have evolved the concept of persistent individual.
Nevertheless, it is analogous behaviour due to analogous circumstances. I believe that people in cities really do have a concept of individual. (Though it might slip in those who carry a grudge against members of a race or class.)
Does the idea of individual help demarcate bodies? It would be nice to think that my are was that important. But I suspect that there are already other criteria to demarcate bodies. And certainly even animals that don't have a notion of individual do demarcate their own and others' bodies.
Note though, I'm interested how often people rely on an unproblematic demarcation of bodies to answer other questions.