The Spartans surely knew what to do with Down Syndrome children and other newborns that were considered less than desirable. Here's one description:
Shortly after birth, a mother would bathe her child in wine to see whether the child was strong. If the child survived it was brought before the Gerousia by the child's father. The Gerousia then decided whether it was to be reared or not. If they considered it "puny and deformed", the baby was thrown into a chasm on Mount Taygetos known euphemistically as the Apothetae (Gr., ἀποθέτας, "Deposits"). This was, in effect, a primitive form of eugenics.
Other stories abound about infants being left on a mountainside to die of exposure. One can legitimately ask how different it is from how Americans abort children that will be born with Down Syndrome. It is reported that 92 percent of those diagnosed with the syndrome are aborted. Nate Hentoff, a prominent civil rights activist, laments the Down Syndrome genocide