Plato, Laws 678b

ἆρʼ οἰόμεθα, ὦ θαυμάσιε, τοὺς τότε, ἀπείρους ὄντας πολλῶν μὲν καλῶν τῶν κατὰ τὰ ἄστη, πολλῶν δὲ καὶ τῶν ἐναντίων, τελέους πρὸς ἀρετὴν ἢ πρὸς κακίαν γεγονέναι; καλῶς εἶπες, καὶ μανθάνομεν ὃ λέγεις. οὐκοῦν προϊόντος μὲν τοῦ χρόνου, πληθύοντος δʼ ἡμῶν τοῦ γένους, εἰς πάντα τὰ νῦν καθεστηκότα προελήλυθεν πάντα; ὀρθότατα. οὐκ ἐξαίφνης γε, ὡς εἰκός, κατὰ σμικρὸν δὲ ἐν παμπόλλῳ τινὶ χρόνῳ.

Do we imagine, my good Sir, that the men of that age, who were unversed in the ways of city life—many of them noble, many ignoble,—were perfect either in virtue or in vice? Well said! We grasp your meaning. As time went on and our race multiplied, all things advanced—did they not?—to the condition which now exists. Very true. But, in all probability, they advanced, not all at once, but by small degrees, during an immense space of time.