From the moment it was born, a Spartan was bred to service the state. If a baby passed inspection with a clean bill of health, he or she would be spared until age seven--agoge season. If a baby showed a visible physical deformity, then that baby would be vulture fodder.
At the age of seven, the child who survived started school. Years of intense training for military strategies, pain tolerances, to name a few resulted in an upstanding Spartan soldier, the envy of all the other Greek military academies.
But agoges were Social Darwinist schools. Many began training, but few survived for long enough to reach graduation.
Despite this detriment, the agoge system worked for a city-state as militaristic as Sparta. But Sparta was just a city.
The military ensured the success of empires. The Romans, the Mongols, the Persians, the Qin, the Franks, the Ottomans, the Russians under command of Ivan Grozny (the Terrible)--they made names for themselves through the might of the armies. They could have easily worked the way the Spartans did, so let's say that in an AH scenario, any one of these empires used infant inspections and agoge disciplines. In the grand scale of empire-building, would these sort of disciplines only augment the issues of population detriments?