Linguistic and archeological evidence indicates that Austronesian speakers first reached Sumatra from Taiwan and the Philippinesthrough Borneo and/or Java about 2,500 years ago, and the Batak probably evolved from these settlers. While the archaeology of southern Sumatra testifies the existence of neolithic settlers, it seems that the northern part of Sumatra was settled by agriculturalists at a considerably later stage.
Although the Batak are often considered to be isolated peoples, largely because they were inland, away from influence by seafaring European colonials, there is evidence that they have been involved with trade and contact with other neighbouring kingdoms for a millennium or more. Reliable historical records of the Batak before 1800 are almost non-existent. The Bata were possibly documented in Zhao Rugua's 13th-century Description of the Barbarous People, which refers to a 'Ba-ta' dependency of Srivijaya. The Suma Oriental, of the 15th century, refers to the kingdom of Bata, bounded by Pasai and the Aru kingdom.
The Bataks were likely involved with trade with Srivijaya for benzoin and camphor, both of which were important commodities for trade with China, and grew in the Batak lands of northwest Sumatra, perhaps from the 8th or 9th centuries, and continuing for the next thousand years, Batak men carrying the products on their backs for sale at ports.
It is suggested that the important port of Barus in Tapanuli was populated primarily by Batak people. A Tamil inscription has been found in Barus dated 1088, while contact with Chinese and Tamil traders took place at Kota Cina, a trading town located in what is now northern Medan that was established in the 11th century, and comprising 10,000 people by the 12th century. Tamil remains have been found on key trade routes to the Batak lands.
These trading opportunities may have caused migration of Batak from Pakpak and Toba to the present-day Karo and Simalungun 'frontier' lands, where they were exposed to greater influence from visiting Tamil traders, while the migration of Batak to the Angkola-Mandailing lands may have been prompted by 8th-century Srivijayan demand for camphor.
The Karo marga or tribe Sembiring "black one" is believed to originate from their ties with Tamil traders, with specific Sembiring sub-marga, namely Brahmana, Colia, Pandia, Depari, Meliala, Muham, Pelawi, and Tekan all of Indian origin. Tamil influence on Karo religious practices are also noted, with the pekualuh secondary cremation ritual specific to the Karo and Dairi people.
From the 16th century onwards, Aceh increased the production of pepper, an important export commodity, and in doing so needed to import rice, which grew well on the Batak wetlands. Batak people in different areas cultivated either sawah "wet rice fields" or ladang "dry rice", and the Toba Batak, most expert in agriculture, would have migrated to meet demand in new areas. The increasing importance of rice had religious significance, increasing the power of the Batak high priests, who had responsibility for ensuring agricultural success.