"The literal interpretation of this portion of the Rámáyana is indeed deeply rooted in the mind of the Hindu. He implicitly believes that Ráma is Vishnu, who became incarnate for the purpose of destroying the demon Rávana: that he permitted his wife to be captured by Rávana for the sake of delivering the gods and Bráhmans from the oppressions of the Rákshasa; and that he ultimately assembled an army of monkeys, who were the progeny of the gods, and led them against the strong-hold of Rávana at Lanká, and delivered the world from the tyrant Rákshasa, whilst obtaining ample revenge for his own personal wrongs.
One other point seems to demand consideration, namely, the possibility of such an alliance as that which Ráma is said to have concluded with the monkeys. This possibility will of course be denied by modern critics, but still it is interesting to trace out the circumstances which seem to have led to the acceptance of such a wild belief by the dreamy and marvel loving Hindi. The south of India swarms with monkeys of curious intelligence and rare physical powers. Their wonderful instinct for organization, their attachment to particular localities, their occasional journeys in large numbers over mountains and across rivers, their obstinate assertion of supposed rights, and the ridiculous caricature which they exhibit of all that is animal and emotional in man, would naturally create a deep impression.… Indeed the habits of monkeys well deserve to be patiently studied; not as they appear in confinement, when much that is revolting in their nature is developed, but as they appear living in freedom amongst the trees of the forest, or in the streets of crowded cities, or precincts of temples. Such a study would not fail to awaken strange ideas; and although the European would not be prepared to regard monkeys as sacred animals he might be led to speculate as to their origin by the light of data, which are at present unknown to the naturalist whose observations have been derived from the menagerie alone.
Whatever, however, may have been the train of ideas which led the Hindú to regard the monkey as a being half human and half divine, there can be little doubt that in the Rámáyana the monkeys of southern India have been confounded with what may be called the aboriginal people of the country. The origin of this confusion may be easily conjectured. Perchance the aborigines of the country may have been regarded as a superior kind of monkeys; and to this day the features of the Marawars, who are supposed to be the aborigines of the southern part of the Carnatic, are not only different from those of their neighbours, but are of a character calculated to confirm the conjecture. Again, it is probable that the army of aborigines may have been accompanied by outlying bands of monkeys impelled by that magpie-like curiosity and love of plunder which are the peculiar characteristics of the monkey race; and this incident may have given rise to the story that the army was composed of Monkeys."
WHEELER'S History of India. Vol. II. pp. 316 ff.