Until five or six thousand years ago, the Red River flowed through Ha Long Bay, which was then dry land, and down through a vast fertile plain that ended near the tip of what is now Hainan Island. Most of this plain is now buried under the waters of the Gulf of Tonkin.
In those ancient times, the river flowed into a sea that was about 120 metres below its present level, like most seas and oceans around the world.
However, as the earth began warming 27,000 years ago at the end of the last ice age, seas around the world began rising gradually until they reached their present levels about 5,000 years ago.
The inundation, part of a world event referred to in ancient Mesopotamian texts and the Bible, swamped a vast area of coastline around the world, particularly in South-east Asia and Australia to the South. This gave birth to oral histories still repeated by native people in Australia and New Guinea – and by all ethnic groups throughout Vietnam. An article on the subject by the late ethnologist Dang Nghiem Van, The Flood Myth and Origin of Ethnic Groups in South-east Asia, was published in 1993.
Vạn, director of the Center for Study of Religion and former vice-director of the Institute of Ethnology in Hà Nội, collected 300 stories of an ancient flood in his travels throughout Vietnam. They were published by the American Folklore Society in its journal. Vạn, Vietnam’s prominent historian and ethnologist, died in 2016.
Geologists today refer to the two pre-flood land masses as Sundaland (Southeast Asia) and Sahul (Australia, Tasmania and New Guinea).
Southeast Asia was then basically one large land mass stretching like a giant udder from what is now Thailand, Cambodia, Laos and Vietnam to embrace Malaysia, Sumatra and most of the islands as far as Java.
It was a vast, fertile region fed by silt from rivers flowing for millenia from the slowly rising Himalayas – including the Red River and the Mekong. The rich plains, including what is today the Gulf of Tonkin, now home to Ha Long Bay, are believed to have held a large population of Austronesian speaking people, including the small, dark Negritos who still remain in pockets throughout former Sundaland – and once even as far as the rainforests of northern Australia and Tasmania.
The seas rose slowly for thousands of years, but at times advanced quite rapidly, as the ice sheets around the world continued to melt. When the warming stopped, somewhere around 5,000 to 7,000 years ago, the shorelines of Asia, Australia and the world had altered dramatically. (Some argue that the warming is an “on-again off-again” work in progress, like even more ancient ice ages).
In the giant Sahul landmass, Australia was cut off from Tasmania and New Guinea, stranding people and animals such as the Tasmanian Tiger. In Sundaland, the solid land mass was broken into a patchwork of islands stretching from mainland Vietnam, Cambodia, Thailand and Malaysia to Sumatra, Java and Borneo in Indonesia.
The “world flood”, as it has been called, is believed to have slowly submerged Sundaland, a vast and fertile cradle of mankind that evolved after early people began a long journey out of Africa 60,000 to 100,000 years ago.
According to historians, the route they took was along the coast of the Middle East and India to Southeast Asia. Why? Because it was the simplest and safest way to migrate – and fishing mostly kept them alive. It is interesting to note that large conch shells were used by these ancient wanderers to communicate with each other along the shores. The conch is still a vibrant symbol in Asian cultures as far away as Tibet.
Some anthropologists believe that the flood led to forced migrations out of Sundaland into the hills and valleys of the Southeast Asia we know today. They compare the high genetic diversity of Southeast Asia to a comparable lack of diversity in northern Asia. In other words, the spread of the Sundaland peoples after the flood triggered the spread of people north into the Eurasian landmass.
The rising waters also isolated elephants, tigers and rhinoceros and even certain types of river fish, often leading to the evolution of a smaller species on smaller territory.
During the Ice Age, Ha Long Bay was connected to Sundaland’s version of the cradle of mankind by a much broader coastline down Vietnam. Excavations reveal pottery and ceramics made on turntables, plus metal instruments dating back 5,000 years. Based on all the artifacts collected so far, Ha Long can be said to possess a developed culture with a complete set of production tools for hunting and harvesting – plus jewelry and woven handicrafts.
One of the ancient stories of the Vietnamese people relates to the frog and its connection with and power over water. Con Coc Isle (Toad Isle) in Ha Long Bay was named after a toad who asked all animals to complain to heavenly gods to end a drought ravaging the land. This meant that the gods had to accept the toad as their uncle. Since then, whenever toads grind their teeth (croak) the gods have to send down rain. In China, it is the dragon who needs appeasing during a drought.
This is one of the old stories that distinguish Vietnamese from their neighbours. Some scholars hold that the toads often found on the ancient bronze drums of the highly creative Đông Sơn culture on the Red River plains demonstrate that ancient Vietnamese were different.
Surveys around Ha Long Bay have shown the presence of prehistoric humans in the area for tens of thousands of years. The successive ancient cultures are the Soi Nhu culture (18,000-7,000 BC), the Cai Beo culture (7,000-5,000 BC) and the Ha Long culture (5,000-3,000 years before the present). These cultures appear related to those that spread around the Gulf of Tonkin and up the coast as far as Guangdong.
A study from Leeds University has suggested that humans have been occupying the islands of Southeast Asia for longer than previously believed. Population dispersals seem to have occurred at the same time as the sea levels rose, which may have resulted in migrations from the Philippines to as far north as Taiwan. This forced migration would have caused these humans to adapt to forest and mountain environments. They were the ancestors of today’s Southeast Asian peoples.
Research held in 2009 by the HUGO Pan Asian SNP Consortium, conducted within and between the different populations of the Asian continent, show that genetic diversity clearly increases the closer one gets to old Sundaland. It also suggests that Southeast Asia was a major geographic source of East Asian, Australasian and North Asian populations.