Son and Lang Rongrien Rockshelter in Krabi, peninsular Thailand. The archaeological data between 18,000 and 3,000 years ago primarily derive from cave and rock shelter sites, and are associated with Hoabinhian foragers. Initial states and Indianized states There are many sites in present-day Thailand dating to the Bronze (1500–500 BCE) and Iron Ages (500 BCE-500 CE). The site of Ban Chiang (around Udon Thani Province) currently ranks as the earliest known center of copper and bronze production in Southeast Asia and has been dated to around 2,000 years BCE. Thailand also participated in the Maritime Jade Road, which existed for 3,000 years, from 2000 BCE to 1000 CE. The oldest known records of a political entity in Indochina are attributed to Funan - centered in the Mekong Delta and comprising territories inside modern day Thailand. Chinese annals confirm Funan's existence as early as the first century CE. Archaeological documentation implies an extensive human settlement history since the fourth century BCE. The region also hosted a number of indigenous Austroasiatic-speaking and Malayo-Sumbawan-speaking civilisations. However, little is known about Thailand before the 13th century, as the literary and concrete sources are scarce and most of the knowledge about this period is gleaned from archaeological evidence. Similar to other regions in Southeast Asia, Thailand was heavily influenced by the culture and religions of India, starting with the Kingdom of Funan around the first century until the Khmer Empire. These "Indianised kingdoms" are composing of Dvaravati, Srivijaya and the Khmer Empire. E. A. Voretzsch believes that Buddhism must have been flowing into Thailand from India at the time of the Indian emperor Ashoka of the Maurya Empire and into the first millennium. Later Thailand was influenced by the south Indian Pallava dynasty and north Indian Gupta Empire. Central Thailand The Chao Phraya River in what is now central Thailand had once been the home of the Mon Dvaravati culture, which prevailed from the seventh century to the tenth century. Samuel Beal discovered the polity among the Chinese writings on Southeast Asia as "Duoluobodi". During the early 20th century archaeological excavations led by George Coedès found Nakhon Pathom Province to be a centre of Dvaravati culture. The two most important sites were Nakorn Pathom and U Thong (in modern Suphan Buri Province). The inscriptions of Dvaravati were in Sanskrit and Mon using the script derived from the Pallava alphabet of the South Indian Pallava dynasty.