Farmers in China’s Yunnan Province have been quietly growing tea for thousands of years. This mountainous region, which borders Vietnam, Laos, and Myanmar, may be the birthplace of Camellia sinensis, the bush that gave rise to all tea. The area’s signature cakes of sun-dried, fermented leaves, known as pu’er, have long been a staple of daily life. To hit the road (specifically, the South Silk Road, which became known as Tea-Horse Road), sellers wrapped dried leaves in bamboo and strapped the discs to their animal. On the journey, traders, horses, and goods were exposed to sunshine, heat, and rain. Fermentation began, perhaps, as nothing more than consequence.
Source: Pu’er – Gastro Obscura