Infanticide Is Nothing New

 and it is tied to the decline of religion, morals and female emancipation:

Greek women participated actively in the cultural pursuits of the time, and contributed to letters, science, philosophy, and art. Aristodama of Smyrna gave recitals of her poetry throughout Greece, and received many honors. Some philosophers, like Epicurus, did not hesitate to admit women into their schools. Literature began to stress the physical loveliness of woman rather than her worth and charm as a mother; the literary cult of feminine beauty arose in this period alongside the poetry and fiction of romantic love. The partial emancipation of woman was accompanied by a revolt against wholesale maternity, and the limitation of the family became the outstanding social phenomenon of the age. Abortion was punishable only if practiced by a woman against the wish of her husband, or at the instigation of her seducer. When a child came it was in many cases exposed. Only one family in a hundred, in the old Greek cities, reared more than one daughter: “Even a rich man,” reports Poseidippus, “always exposes a daughter.” Sisters were a rarity. Families with no child, or only one, were numerous. 

The downfall of Greece