[7] Stretching for several thousand kilometres, the area features a very large number of islands and boasts some of the richest marine, flora and fauna biodiversity on Earth.

[9] The major groupings are: The seven largest islands are Borneo, Sumatra, Sulawesi and Java in Indonesia; and Luzon and Mindanao in the Philippines.

This line divides the flora and fauna of Asia from that of Australia and New Guinea with stretches of water that have always been too wide for plant and animal species to cross readily.

[citation needed] Historically, the region has been referred to as part of Greater India, as seen in Coedes' Indianized States of Southeast Asia, which refers to it as "Island Southeast Asia";[11] and within Austronesia or Oceania, due to shared ethnolinguistic and historical origins of the latter groups (Micronesian and Polynesian groups) being from this region.

[12] The maritime connectivity within the region has been linked to it becoming a distinct cultural and economic area, when compared to the 'mainland' societies in the rest of Southeast Asia.

[17][14] They established trade routes with Southern India and Sri Lanka as early as 1500 BCE, ushering an exchange of material culture (like catamarans, outrigger boats, lashed-lug and sewn-plank boats, and paan) and cultigens (like coconuts, sandalwood, and sugarcane); as well as connecting the material cultures of India and China.

Indonesians, in particular were trading in spices (mainly cinnamon and cassia) with East Africa using catamaran and outrigger boats and sailing with the help of the Westerlies in the Indian Ocean.

This trade network expanded to reach as far as Africa and the Arabian Peninsula, resulting in the Austronesian colonization of Madagascar by the first half of the first millennium CE.

Demand for Southeast Asian products and trade was partially driven by the increase in China's population in this era, whereby it doubled from 75 to 150 million,[24] as well as the loss of access to the northern Silk Road.

Despite not having the official sanction of the Chinese government these communities formed business and trade networks between cities such as Melaka, Hội An and Ayutthaya.

[28] The naval expeditions of Zheng He between 1405 and 1431 also played a critical role in opening up of China to increased trade with Southeast Asian polities.

[22] Shipbuilding of the formerly dominant Southeast Asian trading ships (jong, the source of the English term "junk") declined until it ceased entirely by the 17th century.

[30][31] There was new demand for spices from Southeast Asia and textiles from India and China, but these were now linked with direct trade routes to the European market, instead of passing through regional ports of the Indian Ocean Maritime Silk Road.