There is a widespread concept in Greek and Latin literature of a devolution into civilization from a more contented past "golden age." It is not universal and should not necessarily be taken as something that all Greeks and Romans believed literally, but there was a sense of "once people could get what they needed without care, and did not seek more, but the greedier we get the less happy we are." It's not always treated the same way by all authors. Vergil's famous fourth eclogue describes the golden age that once existed and will return with the birth of a boy (debate exists over precisely whom he meant):

And for you, boy, the uncultivated earth will pour out her first little gifts, straggling ivy and cyclamen everywhere and the bean flower with the smiling acanthus. The goats will come home themselves, their udders swollen with milk, and the cattle will have no fear of fierce lions: Your cradle itself will pour out delightful flowers: And the snakes will die, and deceitful poisonous herbs will wither: Assyrian spice plants will spring up everywhere. And you will read both of heroic glories, and your father’s deeds, and will soon know what virtue can be. The plain will slowly turn golden with tender wheat, and the ripe clusters hang on the wild briar, and the tough oak drip with dew-wet honey.

The poem continues to describe the errors of civilization that will persist into the new world, the elements of civilization that make men unhappy:

Some small traces of ancient error will lurk, that will command men to take to the sea in ships, encircle towns with walls, plough the earth with furrows. Another Argo will arise to carry chosen heroes, a second Tiphys as helmsman: there will be another War, and great Achilles will be sent once more to Troy.

But these will apparently pass away and mankind can return to primordial happiness:

Then when the strength of age has made you a man, the merchant himself will quit the sea, nor will the pine ship trade its goods: every land will produce everything. The soil will not feel the hoe: nor the vine the pruning hook: the strong ploughman too will free his oxen from the yoke: wool will no longer be taught to counterfeit varied colours, the ram in the meadow will change his fleece of himself, now to a sweet blushing purple, now to a saffron yellow: scarlet will clothe the browsing lambs of its own accord.

This surely cannot be meant to describe a real belief that before people invented civilized life, wool spontaneously became whatever colour you wanted. Instead, the literary trope suggests that before mankind tried to tame or rule over nature by plowing the land, cutting down trees, and sailing on the ocean, they received what they needed from it and were without care. Hard work and warfare spring from this debasing need of mankind to rule nature, or spring from some fall of mankind from a state where nature accomodated their needs.

The general sense of this progression from 'happy pre-civilized mankind' to the present state is described by Hesiod as going from a Golden Age as described above; to the Silver Age (generally paired with the development of agriculture and with the overthrow of Saturn/Cronus by Jupiter/Zeus), which in Hesiod is much debased from the happiness of the Golden Age and leads to a universal destruction, and on to the Bronze and Heroic Ages, with violence and warfare in which the heroic figures of the past achieved their greatness, and on to the present-day Iron Age, in which everything is bleak -- mankind has forgotten the rules of piety and hospitality, violence is widespread, right is powerless before injustice, and other dismal concepts.

In this way, then, there is a sense throughout the literature that there was a pre-city life, pre-agricultural way of life, but the overall tendency is to complain of how things have declined since then. Horace attacks those who do nothing but complain of the loss of the simplicity of days gone by and suggests that if mankind was happier living poor on a tiny farm, then perhaps his audience should go and try it. There are piles of other examples, but these are a few to go from.

As to written language being new, I believe Livy mentions the Arcadians as the source of the Roman alphabet, so he definitely records a sense that there was a time before written language, at least in Latin.

The Greeks had an idea that men slowly learned the skills that made them civilized, similar to the understanding we now have but without all the DNA testing and skeletons. This is most clearly seen in their mythology. Prometheus brings fire. Demeter teaches the Greeks how to grow grain. Dionysus teaches them how to make wine. Long story short, the gods gave civilization to the Greeks (although most Greeks had the inclination that the Egyptians and other Near Eastern peoples had been civilized longer and thus wrote myths about how they received knowledge from the gods).

There's a chance that these myths evolved from oral transmission and vague recounts that people gave about what their ancestors used to do. However, I think they were colored by observing peoples like the Scythians who were nomads around the Black Sea and other groups north and west of Greece who had not settled down. The Greeks may have made up this idea of progress as a way to define their superiority to these pesky shepherds who keep trying to steal their produce.

That written language for instance was a new invention and had not always existed?

Plato was certainly aware that written language was a new invention, and offered a pretty scathing criticism of the written-word-as-authoritative-source in his dialog "Phaedrus."

He attests to the Greek view that the Egyptian civilization was older than theirs, and states that it was the Egyptians who developed writing:

At the Egyptian city of Naucratis, there was a famous old god, whose name was Theuth; the bird which is called the Ibis is sacred to him, and he was the inventor of many arts, such as arithmetic and calculation and geometry and astronomy and draughts and dice, but his great discovery was the use of letters. Now in those days the god Thamus was the king of the whole country of Egypt; and he dwelt in that great city of Upper Egypt which the Hellenes call Egyptian Thebes, and the god himself is called by them Ammon. To him came Theuth and showed his inventions, desiring that the other Egyptians might be allowed to have the benefit of them; he enumerated them, and Thamus enquired about their several uses, and praised some of them and censured others, as he approved or disapproved of them. It would take a long time to repeat all that Thamus said to Theuth in praise or blame of the various arts. But when they came to letters, This, said Theuth, will make the Egyptians wiser and give them better memories; it is a specific both for the memory and for the wit. Thamus replied: O most ingenious Theuth, the parent or inventor of an art is not always the best judge of the utility or inutility of his own inventions to the users of them. And in this instance, you who are the father of letters, from a paternal love of your own children have been led to attribute to them a quality which they cannot have; for this discovery of yours will create forgetfulness in the learners' souls, because they will not use their memories; they will trust to the external written characters and not remember of themselves. The specific which you have discovered is an aid not to memory, but to reminiscence, and you give your disciples not truth, but only the semblance of truth; they will be hearers of many things and will have learned nothing; they will appear to be omniscient and will generally know nothing; they will be tiresome company, having the show of wisdom without the reality.

Seems like Plato wasn't a huge fan of the written word!

And it's no surprise that Plato should have these words come from Socrates, who championed inquiry and dialog as the means by which the truth may be fleshed out:

I cannot help feeling, Phaedrus, that writing is unfortunately like painting; for the creations of the painter have the attitude of life, and yet if you ask them a question they preserve a solemn silence. And the same may be said of speeches. You would imagine that they had intelligence, but if you want to know anything and put a question to one of them, the speaker always gives one unvarying answer. And when they have been once written down they are tumbled about anywhere among those who may or may not understand them, and know not to whom they should reply, to whom not: and, if they are maltreated or abused, they have no parent to protect them; and they cannot protect or defend themselves.