China has long been considered one of the locations for original domestication of wild boars (Sus scrofa) but tracking the initial process has always been challenging. In a new study, archaeologists analyzed pig dental calculus (mineralized plaque) from two early Neolithic sites in the Lower Yangtze River region of South China: Jingtoushan (8,300 to 7,800 years ago) and Kuahuqiao (8,200 to 7,000 years ago). Their results indicate that pigs consumed human-associated foods and waste, including cooked starchy plants and human whipworm (Trichuris trichiura) eggs, likely derived from food preparation and fecally contaminated materials.
The wild boar (Sus scrofa). Image credit: Elşad İbrahimov / CC BY-SA 4.0.
Domestication of some animals, including pigs, has often been associated with the Neolithic period when humans began their transition from foraging to farming around 10,000 years ago.
Wild boars are large, aggressive beasts that live independently, many in the forest, rooting for food from the undergrowth.
They have larger heads and mouths, and bigger teeth than domestic pigs.
“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,” said Dartmouth College’s Dr. Jiajing Wang.
“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.”
To study the domestication of pigs and other animals, archaeologists have often relied on examining the sizes and shapes of skeletal structures to mark the morphological change over time.
“But this method can be problematic because the reduction in body size likely occurred later in the domestication process,” Dr. Wang said.
“What probably came first were behavioral changes, like becoming less aggressive and more tolerant of humans.”
So, for the study, Dr. Wang and colleagues used a different method and documented what the pigs had been eating over their lifespan using the molar teeth of 32 pig specimens.
Through a microfossil analysis of the pig teeth, they examined the dental calculus from two of the earliest sites where humans lived, at least 8,000 years ago at Jingtoushan and Kuahuqiao in the Lower Yangtze River region of South China.
The researchers identified a total of 240 starch granules. They found that pigs had eaten cooked foods — rice and yams — as well as an unidentified tuber, acorns, and wild grasses.
“These are plants that were present in the environment at that time and were found in human settlements,” Dr. Wang said.
Prior research has found rice at both sites with intensive rice cultivation at Kuahuqiao, which is located farther inland and has greater access to freshwater than coastal-based Jingtoushan.
Other studies have also shown starch residues in grinding stones and pottery from Kuahuqiao.
“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,” Dr. Wang said.
Human parasite eggs, specifically, that of whipworm — a parasite egg that can mature inside human digestive systems — were also found in the pig dental calculus.
These yellow-brown football-shaped parasite eggs were found in 16 of the pig teeth specimens.
The pigs must have been eating human feces or drinking water or eating food for which the dirt was contaminated by such feces.
“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,” Dr. Wang said.
The scientists also conducted a statistical analysis of the dental structures of the Kuahuqiao and Jingtoushan pig specimens, showing that some had small teeth similar to those of modern domestic populations in China.
“Wild boars were probably attracted to human settlements as people started settling down and began growing their own food,” Dr. Wang said.
“These settlements created a large amount of waste, and that waste attracts scavengers for food, which in turn fosters selection mechanisms that favored animals willing to live alongside humans.”
In animal domestication, this process is called a commensal pathway, where the animal is attracted to human settlements rather than the humans trying to actively recruit the animals.
The data also support that early interaction also involved domestic pigs under active human management, representing a prey pathway in the domestication process.
“Our study shows that some wild boars took the first step towards domestication by scavenging human waste,” Dr. Wang said.
“The research also sheds light on the likely relationship between pig domestication and the transmission of parasitic diseases in early sedentary communities.”
The study was published in the Proceedings of the National Academy of Sciences.
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Jiajing Wang et al. 2025. Early evidence for pig domestication (8,000 cal. BP) in the Lower Yangtze, South China. PNAS 122 (24): e2507123122; doi: 10.1073/pnas.2507123122
