There’s no question that breastfeeding is superior to formula-feeding. Women are made not only to carry a fetus to term and deliver a baby, but also to feed that child early in his or her life to help it grow and develop normally. If everything is working correctly, a new mother will produce enough milk provide all the nutrients the child needs to thrive and develop until he or she can start ingesting solid food.

Unfortunately, some women simply don’t produce enough milk to sustain their newborn. For these children, it’s important to have an alternative source of nutrition.

And when women started entering the workforce in greater numbers — around the middle of the 20th century — the time they had for breastfeeding was limited. If mothers weren’t breastfeeding throughout the day, their milk supply would often decline.

This led to more new mothers searching for alternative food sources for their newborns. In the 19th and early 20th centuries, when a woman could not produce enough milk to sustain her infant, a wet nurse was brought in to nourish the newborn. A wet nurse was another woman who nursed the child. Wet-nursing is thought to have existed 2,000 years ago. For instance, it was documented in ancient Egypt, throughout ancient Rome and Greece, and during the Middle Ages. Qualifications for wet nurses were even described. In more recent times, wet nurses were frequently used by the wealthy who could afford the service.

Although breastfeeding was the preferred method in ancient times, there is evidence of bottle-feeding dating back thousands of years. In those cases, animals’ milk was used in lieu of breast milk. But due to a lack of understanding about how to sterilize containers, many infants died from contamination. It’s estimated that contaminated feeding implements were responsible for one-third of infant deaths.