Wheat and millet dug up by archaeologists in Yunnan hint at previously unknown migrations and may shed light on a mysterious civilisation.

Pottery and grains traditionally found in northern China were recently unearthed in the southwestern province of Yunnan, renewing a long-standing debate about how Chinese civilisation evolved in the region and offering clues about an ancient migration route.

Beijing and Kunming researchers found charred remains of wheat and millet nearly 4,000 years old in Yunnan. The crops are typically cultivated in the Yellow River drainage basin, but not further south. The finding suggests the early settlers in Yunnan cultivated the crop far earlier than previously thought.

"Nobody expected wheat or millet this old from Yunnan," said Peking University researcher Jin Hetian after presenting the findings at an archaeology conference in Fukuoka, Japan, in June.

The findings have not been published in any journals, pending further data analysis. But they could shed new light on Yunnan's Dian people, who are credited with creating one of the four distinct Bronze Age civilisations, a society one researcher described as "almost as mysterious as the Mayans".

More than 1,000 grains of wheat were identified in dirt samples taken from the Haimenkou excavation site in northwest Yunnan, and carbon-dating tests showed the wheat samples were from 1,600BC to 400BC. A few hundred charred millet grains were also found, some dating back to a much earlier era.

Scientists hope that the archaeobotany study - examining plant remains from archaeological sites to understand a certain society's lifestyle and economy - may confirm a long-held, but unproven, theory that millet entered the Indochina peninsula through what is now Yunnan.

The Haimenkou site also offers clues about an ancient migration route across China. Pottery and bronze artefacts unearthed there are strikingly similar to those in the Qijia culture (2400-1900BC) that existed from the Neolithic to the Bronze Age in the north in present-day Gansu province.