A serious problem in trying to model the protolanguage of another species is the difficulty in distinguishing the social-semiotic from the merely social.
On Halliday's model, the social involves the exchange of value, but not symbolic value. That is, the social involves affecting the behaviour of another without the use of expressions of meaning. In terms of Edelman's Theory of Neuronal Group Selection, this is done by activating value systems in the brain.
This is most easily identified in social insects, where the secretion of pheromones affects the behaviour of those detecting them. This is essentially the expansion of intra-brain processes to interactions between brains to co-ordinate behaviour at a social level.
But the courtship displays of male vertebrate animals can also be seen as non-symbolic, despite the attempts of zoologists to interpret them — even the great encumbrance of a peacock's tail — as symbolising male fitness. In this view, a courting male is attempting to affect the behaviour of females by activating positive values in their value systems.
The difficulty, then, lies in distinguishing the social from the social-semiotic, given that the social-semiotic includes the regulatory microfunction 'I want you-&-me…'. On the other hand, it might be taken to demonstrate one evolutionary path from the merely social to the social semiosis of protolanguage.