Research shows how pigs were domesticated from wild boars in China

Analysis of 8,000-year-old teeth has revealed how pigs were first domesticated from wild boars in what is today South China.

The new study, published in the Proceedings of the National Academy of Sciences, is the first to show that pigs were eating the cooked foods and waste from ancient human homes.

“While most wild boars are naturally aggressive, some are more friendly and less afraid of people, which are the ones that may live alongside humans,” says lead author Jiajing Wang, an assistant professor of anthropology at Dartmouth College in the US. “Living with humans gave them easy access to food, so they no longer needed to maintain their robust physiques. Over time, their bodies became smaller, and their brains also became smaller by about one-third.”

Traditional domestication studies focus on skeletal shape of ancient animals.

“But this method can be problematic because the reduction in body size likely occurred later in the domestication process,” says Wang. “What probably came first were behavioural changes, like becoming less aggressive and more tolerant of humans.”

The new study looked at the molars of 32 ancient pigs to see what they were eating over their lifespan. The teeth were from 2 sites where humans lived 8,000 years ago at Jingtoushan and Kuahuqiao in the Lower Yangtze River region of South China.

A total of 240 microfossil starch granules were found showing the ancient pigs ate rice and yams cooked by humans, as well as unidentified tuber, acorns and wild grasses.

“We can assume that pigs do not cook food for themselves, so they were probably getting the food from humans either by being fed by them and/or scavenging human food,” says Wang. “These are plants that were present in the environment at that time and were found in human settlements.”

Eggs of parasites which grow in the human digestive system were also found in the molars. This indicates the pigs were also feasting on human faeces, or drinking water or eating food on dirt contaminated by such faeces.

“Pigs are known for their habit of eating human waste, so that is additional evidence that these pigs were probably living with humans or having a very close relationship with them,” Wang explains.

“Wild boars were probably attracted to human settlements as people started settling down and began growing their own food,” says Wang. “These settlements created a large amount of waste, and that waste attracts scavengers for food, which in turn fosters selection mechanisms that favour animals willing to live alongside humans.”