Modern pet pigs trace their ancestry back to wild boars.A new study indicates that the process of domesticating pigs started in South China more than 8,000 years ago. This discovery offers valuable insights into the long-standing interactions between humans and animals that began in the neolithic era.

Wild pigs (Sus scrofa) are known for their aggressive nature, large size, broad heads, and powerful teeth. Though, not all wild boars are alike. According to Dr. Jiajing Wang from Dartmouth College, “Some wild pigs that are more friendly and not afraid of humans may start living side by side with humans.” This marked the beginning of domesticating these animals.

Living in close proximity to humans provided easy access to food, which led to physical changes in the pigs over time. “their bodies are shrinking, as well as the size of their brains that shrink to one third,” Dr.Wang explained.

Evidence from Pig Teeth: A Look into Ancient Diets

The recent study employed a novel approach by examining dental plaque (dental calculus) on the molars of 32 pig specimens from two Neolithic sites in the Yangtze Hilir river region: Jingtoushan (8,300-7,800 years ago) and Kuahuqiao (8,200-7,000 ago). Instead of only analyzing bone structure, archaeologists investigated the contents of the plaque.

Microscopic analysis revealed 240 starch grains in the pig teeth plaque. The pigs’ diet was similar to that of humans at the time, including rice, sweet potatoes, oak seeds, and weeds. Notably, the starch grains showed signs of cooking, suggesting that the pigs likely obtained food from humans, either through direct feeding or by scavenging food scraps.

“We know that pigs do not cook themselves, so most likely the food comes from human activities,”

“We certainly know that pigs do not cook themselves, so most likely the food comes from human activities,” explained Dr. Wang.

Parasitic Evidence: Close Human-Animal Relationships

The researchers also made a surprising discovery: human whipworm eggs (Trichuris trichiura) were found in the dental plaque of 16 pig specimens.These parasites typically develop in the human body, suggesting that the pigs consumed leftovers or water contaminated with human waste.

“Pigs are known as human waste eaters, and this further strengthens the allegation that they live very close to humans,” said Dr. Wang.

(Mauribo/Canva Pro) Illustration of pig fever.

From Scavengers to Companions: The Domestication Process

This finding supports the theory of commensal pathways in animal domestication. This theory posits that animals are naturally drawn to human environments due to available food sources, rather than being actively tamed by humans from the outset. Over time,animals like pigs that exhibit greater tolerance to human presence are more likely to survive and thrive.

The study also suggests that humans may have begun to actively manage pigs, a process known as prey pathways in domestication.

“Some wild pigs may start the first step towards domestication by scavenging the rest of human waste,” said Dr. Wang.

Implications for Zoonotic Disease Transmission

The discovery of human parasitic eggs in pigs offers new insights into the transmission of parasitic diseases to early human communities. The close interactions between humans and domesticated animals likely facilitated the spread of zoonotic diseases, a significant global health concern today.

This research enhances our understanding of how pigs, now a crucial livestock species, were initially domesticated. By examining traces of food and parasites in dental plaque, a complex and interesting story of domestication emerges, one that began thousands of years ago in the fertile plains of south China.

The findings were published in the scientific journal Proceedings of the National Academy of Sciences (PNAS), paving the way for further research into the evolution of human-animal relationships.