As far as the dark ages go, this wikipedia article basically states what I have learned in school: http://en.wikipedia.org/wiki/
Note the large number of references, and their quality.
Note also that the concept of "dark ages" as "unenlightened, tribal, and barbaric times" is specifically propaganda of the anti-religious "enlightenment". The true irony here is that I would call Rome, toward its end, a far darker place than ever the dark ages were. The difference is simply this: Humility. The most striking thing about the dark ages - which are by some called the "age of faith" - is that there is so little written record of them. On the whole, from what we can tell, people went on farming, shopping, trading, slowly expanding their worlds, sometimes invaded, but rarely in fear, but without kings demanding their deeds be written down, without great popes and empires demanding future and present praise.
It was clearly not a time of silence, though. Look to the cathedrals. Look to Chartres. Made in the midst of that "dark age" it stands as, perhaps, one of the pinnacles of man's creation - and it is a humble thing, as Orson Welles said "without a signature." In fact, it could not be signed, for it was the accretion of time, it was a culture, slowly building up a building, over hundreds of years.
Welles' clip is here, and is well worth watching: http://www.youtube.com/watch?
This is just one example, though perhaps their silence is the best example - that they did not think to raise their monument in stone or word does not necessarily indicate that they were dark, it may indicate that they were humble, and only a thoroughly unenlightened age would think that silence equals barbarity.
Perhaps they did not raise a monument because they knew their debt to the past, and did not want to claim it as their own.
So often we forget, in the midst of our obsession with private enterprise and private worth, that so much of our work, signed, owned, copyrighted, is such an accretion. We all build on the castles and cathedrals of the past. Every western musical artist is a son of Bach. Every western philosopher is a son of Plato - if a wisely rebellious offspring. Our medicines do not arise from the valiant work of a few, experimenting on into the night, proving everything - but from a vast machine, stretching back decades, sometimes centuries, sometimes to men who are dead, always to the acclaimed, the nameless, the fathers, the lovers, the brothers.
We are not alone. I think if any age understood that, it was this strangely silent time.
It had its problems. It had its wars. Its crusades. Its barbarians. As did Rome, and Greece. As we do now. The Enlightenment praised Rome - a place where emperors killed children - where even Harod had the power of life and death over the Children of Bethlehem, and praise it over the Dark Ages, out of which struggle the high medieval period and the renaissance arose - all with their particular problems, perhaps better, perhaps worse, who can say, but each, also, with their joys, and with their lights.
A poem fitting for the subject:
Curiously enough, written by Alexander Pope, of the Enlightenment period.
Happy the man, whose wish and care
A few paternal acres bound,
Content to breathe his native air
In his own ground.
Whose herds with milk, whose fields with bread,
Whose flocks supply him with attire;
Whose trees in summer yield him shade,
In winter fire.
Blest, who can unconcern`dly find
Hours, days, and years, slide soft away
In health of body, peace of mind,
Quiet by day.
Sound sleep by night; study and ease
Together mix`d, sweet recreation,
And innocence, which most does please
Thus let me live, unseen, unknown;
Thus unlamented let me die;
Steal from the world, and not a stone
Tell where I lie.