Reference of pronoun in the context

There have been vigorous arguments among biologists about whether complicated goal directed behavior among high mammals is reliable evidence for their consciousness. Indeed the admission of consciousness into animal research is quite a recent phenomenon. Injury-avoidance behavior is often based on reflexes, and it is not completely obvious that the inner sensation of pain must be attached to it. Even in our own case pain is often felt only after the limb has been moved away.

Here, what does it refer to?
consciousness or reflexes? So difficult to me