Study shows pig domestication began 8,000 years ago in southern China

A new study led by scientists from Dartmouth College unveiled the origins of pig domestication, revealing that the process began in southern China approximately 8,000 years ago during the Neolithic period when humans transitioned from foraging to farming. The findings, published in the Proceedings of the National Academy of Sciences (PNAS) journal, shed light on the early relationship between humans and pigs and the domestication process that has shaped the animals we know today.

The research is the first to determine that pigs consumed human-made food, including cooked foods and waste, suggesting a close relationship between humans and pigs from the very beginning. The team conducted a microfossil analysis of pig teeth from two of the earliest Neolithic sites in the Lower Yangtze River region of South China: Jingtoushan (8,300–7,800 years ago) and Kuahuqiao (8,200–7,000 years ago).

"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," said Dr. Jiajing Wang, the lead author of the study, according to Phys.org.

The analysis revealed that pigs ate cooked starchy plants such as rice, sweet potatoes, and an unknown type of tuber, as well as wild grasses. This diet mirrors that of humans at the time, indicating an overlap in food sources. Additionally, the researchers discovered eggs of human parasites, particularly whipworm (Trichuris trichiura), in the dental calculus of the pigs. This indicates that the animals likely consumed food scraps or water contaminated with human feces, posing a risk of infection due to their close proximity to humans.

"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 added.

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Over time, domesticated pigs experienced a decrease in body and brain size by approximately one-third due to their living conditions alongside humans. The analysis showed that some pig specimens had small teeth similar to those of modern domesticated pigs in China, providing the oldest findings related to pig domestication.

The domestication process occurred in two stages, beginning with behavioral changes such as reduced aggression and increased tolerance of humans, preceding physical or morphological changes. Wild boars, which are large and often aggressive animals living independently in forests and foraging in the underbrush, began to alter their behavior as they interacted more with human settlements.

"What likely came first were changes in behavior, such as becoming less aggressive and more tolerant towards humans," Wang stated.

The researchers suggest that some wild boars may have initiated the first steps toward domestication by scavenging human waste. "These settlements created a large amount of waste, and that waste attracts scavengers for food, which in turn fosters selection mechanisms that favor animals willing to live alongside humans," Wang explained.

This process aligns with what is known in animal domestication as a "commensal pathway," where animals are attracted to human settlements rather than humans actively recruiting them. The data supports that early interactions involved pigs under active human management, representing this commensal pathway in the domestication process.

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