The bones of dogs, pigs, and humans are shedding light on the rise of civilization in China. These remains contain a signature of the plants that all three species ate at the time and suggest that the ancient Chinese may have farmed millet before rice, new research shows.
The millet group of plants, like rice and wheat, are grasses that produce small, edible seeds. Archaeologists have long known that they were domesticated very early in China and India; the earliest known noodles, which are 4000 years old and were reported by a Chinese team in 2005, were made of millet. Although rice was domesticated in China's warm and humid south, millet was domesticated in the north of the country, where conditions were much colder and drier. Yet archaeologists have debated whether these developments were independent or whether rice farmers from the south migrated north and began to cultivate wild millet--which grows much better than rice does in cold and dry conditions--thus transforming it into domesticated varieties.
A Chinese-American team led by Loukas Barton, an archaeologist at the University of California, Davis, and Seth Newsome, an ecologist at the Carnegie Institution of Washington in Washington, D.C., tackled the debate at the early farming village of Dadiwan in northwest China. Dadiwan, which was first settled about 8000 years ago and produced China's earliest known painted pottery, was excavated in the 1970s and again in 2006. The site contains some fossilized fragments of millet, which is the main plant found there, but not enough to elucidate its domestication.
So the team looked instead at the remains of dogs, pigs, and humans who appear to have consumed the grain. Millet is a so-called C4 plant, which has a very efficient photosynthetic system for capturing carbon dioxide, whereas most other plants that grow in northern China are less efficient C3 plants. Because C4 plants concentrate more of carbon's heavier isotopes compared with C3 plants, a technique called stable isotope analysis--which measures the relative concentrations of isotopes in animal bones--can often detect which plants predominate in the diet.
The team found that the isotopic signature of bones located at the site changed over time. In the first phase of occupation at Dadiwan, between 7900 and 7200 years ago, pigs ate only C3 plants, whereas most of the dogs had C4 signatures, meaning that they ate millet. (Human bones from this phase were not available for analysis.) But during the second occupation phase, 6500 to 4900 years ago, all human and dog bones, and the great majority of pig bones, showed strong C4 signatures, indicating that all of their diets contained a lot of millet.
The team, which reports its results online this week in the Proceedings of the National Academy of Sciences, concludes that millet was farmed at Dadiwan in its earliest phases but not by rice farmers from the south. Rather, the presence of pigs with C3 signatures implies that they were wild; the early dogs with C4 signatures, on the other hand, were probably domesticated and being fed millet by humans. That means Dadiwan was likely settled by local hunters who were farming on the side. Later, when millet farming intensified, it became the mainstay of an integrated agricultural system that included millet-eating domesticated pigs and dogs. These findings, the team says, suggest that millet farming helped fuel the rise of the Yangshao culture, one of north-central China's most important early civilizations.
Dorian Fuller, an archaeologist at University College London, calls the report "an important new study" that "provide[s] a novel methodology for thinking about the development and intensification of agriculture." Moreover, Fuller says, domestication of millet was apparently under way in northern China at a time when farmers in the south were just beginning to cultivate wild rice. The study provides definitive evidence "for millet agriculture developing earlier than full-fledged rice agriculture."