Foundlings provide source for Roman Slavery

"When Tiberius and his successors followed in general Augustus' advice of confining the empire within its present frontiers (Tac. Ann. 1.11.7), one of the principal sources of slaves i.e. prisoners of war, seriously decreased. However, as far as we are aware, no major emergency in the replenishment of slave numbers occurred. The reason surely is that the considerable range of other slave sources already available were together able to make up sufficiently for the shortfall. Yet, of these sources, only two, vernae and foundlings, could, we are convinced, have been major contributors. Vernae certainly were important, yet, if the arguments and estimates given above are sound, vernae would have fallen well short of supplying the full yearly requirement. That leaves foundlings. Since we know that child exposure was a widespread phenomenon - urban as well as rural - over a considerable section of the Greek world, Asia Minor, Egypt, Italy and elsewhere in the West, we may conclude that enslaved foundlings were more or less able to make up for the shortage in the slave supply caused by the drop in the numbers of prisoners of war in the first century and a half of the empire - a shortage which vernae and the other sources could not offset. "