Laudator Temporis Acti

Theognis 183-192 (tr. T.F. Higham):

Ram, ass and horse, my Kyrnos, we look over
With care, and seek good stock for good to cover;
And yet the best men make no argument,
But wed, for money, runts of poor descent.
So too a woman will demean her state
And spurn the better for the richer mate.
Money's the cry. Good stock to bad is wed
And bad to good, till all the world's cross-bred.
No wonder if the country's breed declines,—
Mixed metal, Kyrnos, that but dimly shines.

κριοὺς μὲν καὶ ὄνους διζήμεθα, Κύρνε, καὶ ἵππους
    εὐγενέας, καὶ τις βούλεται ἐξ ἀγαθῶν
βήσεσθαι· γῆμαι δὲ κακὴν κακοῦ οὐ μελεδαίνει        185
    ἐσθλὸς ἀνήρ, ἤν οἱ χρήματα πολλὰ διδῷ,
οὐδὲ γυνὴ κακοῦ ἀνδρὸς ἀναίνεται εἶναι ἄκοιτις
    πλουσίου, ἀλλ᾽ ἀφνεὸν βούλεται ἀντ᾽ ἀγαθοῦ.
χρήματα γὰρ τιμῶσι· καὶ ἐκ κακοῦ ἐσθλὸς ἔγημε
    καὶ κακὸς ἐξ ἀγαθοῦ· πλοῦτος ἔμειξε γένος.        190
οὕτω μὴ θαύμαζε γένος, Πολυπαΐδη, ἀστῶν
    μαυροῦσθαι· σὺν γὰρ μίσγεται ἐσθλὰ κακοῖς.

See M.F. Ashley Montagu, "Theognis, Darwin, and Social Selection," Isis 37.1/2 (May, 1947) 24-26, and Radislav Hošek, "Die Mischbevölkerung," Listy filologické 106.3 (1983) 155-159.