He was very clear about Adam and Eve being specially created and the question of them evolving from apes would never have occured to him.
`except inasmuch as this person [his descendant] receives his nature from his first parent, for which reason it is called the `sin of nature'' Since, ``the soul is the form and nature of the body, in respect of its essence and not in respect of its powers...the soul is the subject of original sin chiefly in respect to essence'' (Ibid. IaIIae.83.2; New Advent).
He is spliting a theological hair there, it's not an easy one to deal with. Something physical is passed on from original sin but what that is in biological terms is something the Scriptures don't say anything about.
``whoever maintains that human nature at any period required not the second Adam for its physician, because it was not corrupted in the first Adam, is convicted as an enemy to the grace of God'' (On the Grace of Christ and on Original Sin II.34; Fathers of the Church)
That one is crystal clear on the only theological issue, you can't reject Adam as the first created man and embrace St. Augustine's theology. Notice this is a discussion of the Fathers of the Church so here he is appealing to tradition. Elsewhere he appeals to the testimony of Scripture and he is very dogmatic about what it means to be an enemy of the grace of God.
Chapter 21.—That There Was Created at First But One Individual, and that the Human Race Was Created in Him.
Now that we have solved, as well as we could, this very difficult question about the eternal God creating new things, without any novelty of will, it is easy to see how much better it is that God was pleased to produce the human race from the one individual whom He created, than if He had originated it in several men. For as to the other animals, He created some solitary, and naturally seeking lonely places,—as the eagles, kites, lions, wolves, and such like; others gregarious, which herd together, and prefer to live in company,—as pigeons, starlings, stags, and little fallow deer, and the like: but neither class did He cause to be propagated from individuals, but called into being several at once. Man, on the other hand, whose nature was to be a mean between the angelic and bestial, He created in such sort, that if he remained in subjection to His Creator as his rightful Lord, and piously kept His commandments, he should pass into the company of the angels, and obtain, without the intervention of death, a blessed and endless immortality; but if he offended the Lord his God by a proud and disobedient use of his free will, he should become subject to death, and live as the beasts do,—the slave of appetite, and doomed to eternal punishment after death. And therefore God created only one single man, not, certainly, that he might be a solitary, bereft of all society, but that by this means the unity of society and the bond of concord might be more effectually commended to him, men being bound together not only by similarity of nature, but by family affection. And indeed He did not even create the woman that was to be given him as his wife, as he created the man, but created her out of the man, that the whole human race might derive from one man.
http://www.newadvent.org/fathers/120112.htm
St. Augustine like all theologians spends a lot of time on Genesis, clearly it's a foundational text. He even says that Eve was not created in the same sense since she was taken out of Adam which clearly indicates a literal interprutation.
In fact, if what I'm getting about St. Augustine is correct he took it so literal that he considered the creation to be instantaneous. One thing is for sure, he was no old earth cosmologist and his concern about the length of days was theological. He spends a considerable amount of time on the seventh day but considered the first six to be a logical framework rather then a passage of physical time. Of course as a theologian he had bigger issues to deal with, I doubt seriously the actual length of days was of any great interest to him.
, in a totally non-gay, brother/sister-in-christ kinda way 
