From the Sumerians down to the time of Augustine, all over Europe and Asia, most people agreed that if you had a newborn baby that you didn’t want, you could kill it. Or at least you could abandon it somewhere and not take care of it. Killing a baby is infanticide, and leaving it somewhere is exposure.
Sometimes, the father decided whether to keep a baby or not. Of course most fathers wanted to keep their babies. And most of the time they did. But sometimes they felt raising their baby was not the right thing to do. Sometimes fathers or mothers decided to expose a baby if it seemed to be sick or for some reason was not likely to live anyway. If there was something seriously wrong with the baby’s heart or stomach, then ancient people could not do surgery to fix that. The baby would probably die anyway in a few days.
Other babies were exposed because they were physically challenged. Maybe they couldn’t see or hear. Or they were born with only one arm or one leg, or with spinal bifida. Maybe their parents felt they couldn’t take care of them. (But some people did care for their physically challenged babies.)
Sometimes if there were twins, the parents would expose one of the two babies, because people thought twins were unlucky. Sometimes parents abandoned girl babies, because they wanted a boy.
In very poor families, sometimes parents exposed their babies because the family didn’t have enough food to feed everyone. If there wasn’t enough food to go around, the parents might decide it was better to give the food to the older kids and save them.
Other babies were abandoned by other people, not their parents. For slaves, their owner decided whether to keep them or abandon them. Even some free people were so much under the power of the government or a rich patron that someone else would decide for them. In ancient Sparta, for example, the government decided whether you could keep your baby.
Most of the babies who were exposed probably died. But people who couldn’t have babies themselves and wanted to adopt a baby sometimes took one home. Slave dealers picked up other exposed babies and raised them as slaves. They sold the children when they grew up. Mothers and fathers who had to expose their babies always wanted to think that their baby had been saved (this is the plot of many Greek and Roman plays – Oedipus, for example).
After most people in Europe converted to Christianity, around 400 AD, infanticide and exposure became less common. The Church said that babies had souls too and so it was murder to kill them or let them die. Still this did not stop many people from leaving babies on the steps of churches for somebody else to take care of. These abandoned babies often also died.