In re: "
Where did the people go after the city was abandoned? Did they create a new civilisation or revert to a more primitive state?"
First of all, while 'ancient' in terms of what is there today, it pays to remember that Angor Wat was built, inhabited, and abandoned between the Viking Age and the European age of discovery. So it is not all that 'ancient'.
Second, the people who built Angor still live in Cambodia, which is much diminished from its previous size, having lost wars to the Burmese, Thai, Cham, and lastly, the Vietnamese, who began moving into the Mekong Delta (Kampuchea Krom, or Lower Cambodia) in 1698. The Khmer were just one of many Indochinese states set up along Indian lines. Referred to as a "Mon-Khmer", they are likely the same people who inhabited ancient Funan (chinese name), whose spice, woods, and exotic animal products were traded as far away as Rome, if the Roman coins found at Oc Eo in the Mekong Delta are to be believed. Other states noted in what today is Central and southern Central Vietnam were the five Cham kingdoms of Indrapura (modern Danang), Amaravati, Vijaya (modern Qui Nhon), Kauthara (modern Nha Trang), and Panduranga (modern Phan Rang), who were likewise Hindu and used similar architecture on a much smaller scale (a Cham tower can be seen in Nha Trang). Most of the Highland tribes of the Central Highlands are Mon-Khmer in origin (Bahnar, Sedang, Jeh Katu, Rengao, Halang, Mnong), perhaps examples of Angor groups who reverted to a more primitive state, while the largest tribes, the Jarai and Rhade, are Malayo-Polynesians believed related to the Cham. Some historians now view the tribal peoples of Indochina as most likely representing the original culture and peoples of the peninsula, who spun off what became the Cambodian and Vietnamese cultures. (the Thai peoples who came south later also adopted Indian cultural characteristics). After Vietnam settled the Mekong Delta in the 18th and 19th centuries, they made Cambodia a virtual colony. Though some histories point out that it was legally a 'protectorate', King Ming Manh's "vietnamization" measures of the 1820s and 30s applied equally to upper Cambodia and the Mekong Delta. The French likely saved Cambodia from total absorption into Vietnam by ending the Vietnamese 'protectorate' around 1858, and thereafter allowed Cambodian populations in the Delta to be ruled from Phnom Penh in certain matters (such as being drafted into the Cambodian Army). That ended n 1949 when the French recognized Cochinchina as an integral part of Vietnam, an act that modern Cambodian nationalists see as one of betrayal. In very early 1946, when the French were desperately short of troops to face the emerging Viet Minh, the Cambodian government drafted two battalions of troops for French service. One was raised in Cambodia itself, with the second coming from the Mekong Delta. Likewise, when Lon Nol rebelled against the Sihanouk government, entire rebel Cambodian units fighting with U.S. Special Forces and the ARVN government moved into Cambodia to fight the Khmers Rouges.
So, the bottom line is that you can find the descendants of the peoples who built Angor Wat walking around today in Cambodia itself, as well as in parts of eastern Thailand, and southern Vietnam. And they include tribal peoples, citizens of modern Cambodia, and the Khmer minorities of Thailand and Vietnam.
Edited by lirelou - 06-Jan-2012 at 00:46