A recent study found that prehistoric babies drank milk from ceramic sippy cups, including some with cute animal motifs. Lest you be overwhelmed by the cuteness, there's a heartbreaking side to that discovery: Bronze and Iron Age parents buried their dead infants with their clay sippy cups.

A team of archaeologists found microscopic traces of livestock milk in three of the containers: two from Iron Age graves in Germany dating between 800 and 450 BC, and a broken one from a much earlier Bronze Age grave nearby. The results suggest that feeding babies milk from livestock may have helped early European farming populations grow and expand.

Not Kidding Around

Archaeologists have reconstructed surprising details of ancient people’s lives, but they still know relatively little about how infants and children in the ancient past lived. “Infants and children were mainly ignored in archaeology until about 20 years ago,” University of Otago anthropologist Sian Halcrow, who was not involved in the study, told Ars Technica. “Research projects that are interested in children are starting to reexamine previous assumptions about activities and objects in archaeology—some items that were thought to be ritualistic are in fact child toys.”

That may sound like child’s play—or at least like a really esoteric research interest. But if we want to understand the growth and expansion of ancient populations, we need to understand how (and when) ancient people fed and weaned their babies.

In Southeastern Europe, starting around 7000 BC, people began farming and raising livestock after millennia of hunting and gathering. Archaeologists studying ancient human remains noticed that around the same time, populations in early farming cultures started to grow. Somehow, the shift to farming triggered a prehistoric baby boom, and some archaeologists think livestock milk may have been the key.

Fueling a Prehistoric Baby Boom

Once ancient people started raising cows, goats, and sheep, they had access to animal milk for the first time. Milk would have given Neolithic mothers something extra to feed their babies, either as a supplement or to help wean them off breastfeeding. Given that, it makes sense that around 7000 BC, small clay vessels (about 50 mm wide) with little spouts start showing up at archaeological sites around Central and Eastern Europe. The vessels come in a range of shapes and sizes; some are round, open bowls with a spout on one side, others are long and narrow like pipes, and others are shaped like rabbits or other animals. They remained a staple of life in the region through the Bronze Age and into the Iron Age.

At first, some archaeologists suggested that the spouted vessels might have been used to feed sick or disabled adults—and there was no way to be certain that the vessels (even the cute animal-shaped ones) were for infants. Dunne and her colleagues recently found three of these little spouted vessels buried with Iron Age infants and toddlers in Germany. With little doubt about who the ancient sippy cups belonged to, the vessels are direct evidence of how Iron Age infants were fed—and a strong hint about what all those other little spouted vessels in the archaeological record were for.

In a study that will probably make you want to take a hard look at your own dishes, Dunne and her colleagues found traces of 3,000-year-old fatty acids from ancient milk still clinging to the insides of the vessels. “The lipids are absorbed into the fabric of the pot itself,” Dunne told Ars. The amount of material the archaeologists found suggested that the vessels had seen a lot of use—or had been filled with milk before being placed in the children’s graves.

The molecules soaked into the walls of the little ceramic bottles included palmitic and stearic acids, which are usually the product of degraded animal fats, along with shorter-chain fatty acids that Dunne and her colleagues identified as the remnants of fresh milk fats. The proportions of carbon-13 in the fatty acids suggested that the milk had come from ruminants, such as cows, sheep, or goats. (Carbon-13 is a stable isotope of carbon, and its presence can tell archaeologists about the sorts of plants an animal ate during life.)

In one of the vessels, the types of fatty acids present, and their carbon-13 ratios, suggest that someone had mixed either human breast milk or a thin gruel made from pig fat with the livestock milk. It’s sometimes possible, based on certain proteins, to identify whether lipids came from cows or sheep and goats (telling sheep and goats apart from the chemical makeup of their milk, centuries later, is much harder).

“This paper is important, as it is the first direct evidence for animal milk being contained in these bottles for feeding to babies,” Halcrow told Ars. Since the Iron Age baby bottles from Bavaria look so similar to the ones being used thousands of years earlier during the Neolithic, it’s reasonable to speculate that the practice may have been much older, but archaeologists will need to study those earlier vessels directly to say for sure.

Dunne and her colleagues also hope to study similar vessels from other cultures. “Similar vessels, although rare, do appear in other prehistoric cultures (such as Rome and ancient Greece) across the world. I also know of some in a prehistoric site in Africa (roughly the same age),” Dunne said. “Ideally, we’d like to carry out a larger geographic study and investigate whether they served the same purpose.”

Milk Does a Body Good—Sort Of

The discovery also raises important questions about how feeding infants milk from livestock could have impacted their health. Feeding a baby any sort of milk in a container during the Iron Age risked also feeding the baby a lot of the bacteria that would grow in the vessel. That could have put infants at risk for gastroenteritis and other life-threatening infections.

“We simply do not know whether prehistoric people would have cleaned them, but whether they did or not, bacteria would still grow on them,” Dunne said. The amount of lipid residue Dunne and her colleagues managed to extract from the vessel walls isn’t a sign of sloppy ancient dishwashing, as the walls of the ceramic vessel tend to soak up the lipids. But that underscores how hard it would have been for people to get these containers clean enough to stop harmful bacteria from growing inside. Unpasteurized livestock milk can also transmit zoonotic diseases.

Ruminant milk has a slightly different mix of nutrients from human milk, and those nutritional differences could have been important for prehistoric infants. Cow’s milk tends to have fewer carbohydrates and more protein than human breast milk, and the fats come in larger globules that may be harder for infants’ bodies to absorb.

“Human breast milk contains the ideal amounts of carbohydrates, protein, fat, vitamins, minerals, digestive enzymes and hormones. It also provides protection from infection because it contains numerous types of immune cells,” Halcrow said. “Some of the sugars it contains, although not digested by babies, support certain communities of gut microorganisms, which prevent disease-causing microbes from establishing a presence in the body.”

But livestock milk could still have been very useful as a supplementary source of food for babies, and it could have enabled prehistoric mothers to wean their babies earlier. That, in turn, may have contributed to the population boom. Most women experience a period of infertility while they’re breastfeeding, so longer breastfeeding times mean longer gaps between births. In a society without birth control, shorter weaning time means more babies, which ultimately means a larger population. That's especially critical during a time when archaeologists estimate that only about half of babies survived to adulthood.

To better understand how all those factors interacted to shape the health of prehistoric babies and the growth of early farming populations in Southeastern and Central Europe, archaeologists need to undertake the grim task of studying more infant and child remains from Neolithic, Bronze Age, and Iron Age cemeteries. Isotopic ratios in children’s teeth can suggest how old a baby was during weaning, and bones and teeth also hold evidence of malnutrition or disease. A survey of ancient graves could also give archaeologists clues about infant mortality rates in prehistory.

Meanwhile, an earlier study suggested that ancient cheese may have helped feed older children once lactose intolerance had kicked in.

Nature, 2019. DOI: 10.1038/s41586-019-1572-x (About DOIs).

This story originally appeared on Ars Technica.

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