Consciousness is really only a net of communication between human beings; it is only as such that it had to develop; a solitary human being who lived like a beast of prey would not have needed it.

--- Friedrich Nietzsche, The Gay Science, trans. Walter Kaufmann (1887; New York: Vintage, 1974) p. 298, quoted in Seeing Red, Nicholas Humphrey (Belknap Press of Harvard University Press, 2006) p. 104

More Nietzsche in the same vein from Seeing Red, same page:

"To understand another person, that is to imitate his feelings in ourselves, we . . . produce the feeling in ourelves by imitating with our own body the expression of his eyes, his voice, his walk, his bearing. Then a similar feeling arises in us in consequence of an ancient association between movement and sensation. We have brought our skill in understanding the feelings of others to a high state of perfection and in the presencec of another person we are always almost involuntarily practicing this skill."

Friedrich Nietzshe, "Daybreak," in A Nietzsche Reader, ed. and trans. R. J. Hollingdale (1881; Harmondsworth: Penguin, 1977), p. 156