The history of tea spreads across multiple cultures over the span of thousands of years. With the tea plant Camellia sinensis native to East Asia and probably originating in the borderlands of southwestern China and northern Burma. one of the earliest tea drinking is dated back to China's Shang dynasty, in which tea was consumed as a medicinal drink. An early credible record of tea drinking dates to the 3rd century AD, in a medical text written by Chinese physician Hua Tuo. It first became known to the western world through Portuguese priests and merchants in China during the early 16th century. Drinking tea became popular in Britain during the 17th century. The British introduced commercial tea production to British India, in order to compete with the Chinese monopoly on tea. Geographic origins Camellia sinensis originated specifically around the intersection of latitude 29°N and longitude 98°E, the point of confluence of the lands of southwest China, Tibet, north Burma, and northeast India. The plant was introduced to more than 52 countries, from this centre of origin. On morphological differences between the Assam and Chinese varieties, botanists have long asserted a dual botanical origin for tea; however, statistical cluster analysis, the same chromosome number (2n=30), easy hybridization, and various types of intermediate hybrids and spontaneous polyploids all appear to demonstrate a single place of origin for Camellia sinensis—the area including the Yunnan and Sichuan provinces of China, and northern part of Burma. Yunnan Province has also been identified as "the birthplace of tea...the first area where humans figured out that eating tea leaves or brewing a cup could be pleasant." Fengqing County in the Lincang City Prefecture of Yunnan Province in China is said to be home to the world's oldest cultivated tea tree, some 3,200 years old. According to The Story of Tea, tea drinking likely began in Yunnan province during the Shang Dynasty (1500 BC–1046 BC), as a medicinal drink. From there, the drink spread to Sichuan, and it is believed that there "for the first time, people began to boil tea leaves for consumption into a concentrated liquid without the addition of other leaves or herbs, thereby using tea as a bitter yet stimulating drink, rather than as a medicinal concoction." Scholars believe that tea drinking likely originated in the southwest of China and that the Chinese words for tea may have been originally derived from the Austro-Asiatic