Greek Mythology always portrays the Titan King Kronos as an evil god as he swallowed his children when they were born. However, is reign was the Golden Age, where human race was at its pinnacle. Can you explain me about this paradox? Also can you tell me how were the humans before the arrival of the gods?
first of all I have to point out that you cannot expect that Greek mythology, as well as all the other mythologies, are rational, i.e. based on reason, since Greek gods have been created by the Greek people to explain the existence and working of natural phenomena, that people feared, so that mankind needed to believe in a supernatural/divine help which was per se decisive.
Therefore no rationality there is in Greek mythology and then it is not a paradox the fact that Kronos, the god who devoured his own children, is also the King of the Golden Age, a time of prosperity, peace and general ease, when the animals spoke with a human voice and men had justice and sincerity of the soul, and were good-hearted, altogether guileless, and blest with felicity, as we read in many authors such as e.g. Plato (4th B.C), Callimachus (3rd B.C.) and Diodorus Siculus (1st B.C.).
Kronos –just meaning “time” in ancient Greek- symbolised the destructive ravages of time, which consumed all, including his children, while as the King of the Golden Age, and of the Islands of the Blessed, he represented the passing of the ages as well as the passage of mankind from a rude way of living to civilized life.
As for your question on “how were the humans before the arrival of the gods”, please note that no god really arrived, but simply each god was invented by the needs and fears of men who yearned to have some tutelary deities that helped them in any painful circumstances in exchange for an offering to the gods.
Plato, Laws 713a (trans. Bury) :"[Plato employs the myth of the Golden Age of Kronos in his description of an ideal state ruled by a philospher-elite :] Long ages before even cities existed . . . there existed in the time of Kronos, it is said, a most prosperous government and settlement . . . Well, then, tradition tells us how blissful was the life of men in that age, furnished with everything in abundance, and of spontaneous growth. And the cause thereof is said to have been this : Kronos was aware of the fact that no human being is capable of having irresponsible control of all human affairs without becoming filled with pride and injustice; so, pondering this fact, he then appointed as kings and rulers for our cities, not men, but beings of a race that was nobler and more divine, namely, Daimones (Spirits). He acted just as we now do in the case of sheep and herds of tame animals: we do not set oxen as rulers over oxen, or goats over goats, but we, who are of a nobler race, ourselves rule over them. In like manner the god, in his love for humanity, set over us at that time the nobler race of Daimones who, with much comfort to themselves and much to us, took charge of us and furnished peace and modesty and orderliness and justice without stint, and thus made the tribes of men free from feud and happy. And even today this tale has a truth to tell, namely, that wherever a State has a mortal, and no god, for ruler, there the people have no rest from ills and toils; and it deems that we ought by every means to imitate the life of the age of Kronos, as tradition paints it."
Callimachus, Iambi Fragment 192 (from Oxyrhynchus Papyri 7) : "[In the Golden Age when Kronos ruled :] It was the time when birds and creatures of the sea and four-footed animals could talk in the same way as the Promethean clay .... in the time of Kronos, and even before. Just is Zeus, yet unjust was his ruling when he deprived the animals of their speech, and--as though we were in a position to give part of our voice to others--diverted it to the race of men."
Diodorus Siculus, Library of History 5. 66. 4 (trans. Oldfather) (Greek historian C1st B.C.) :"Kronos, since he was the eldest of the Titanes, became king and caused all men who were his subjects to change from a rude way of living to civilized life, and for this reason he received great approbation and visited many regions of the inhabited earth. Among all he met he introduced justice and sincerity of the soul, and this is why the tradition has come down to later generations that he men of Kronos’ time were good-hearted, altogether guileless, and blest with felicity".