The natural history of our species is dominated by one very significant natural event over the last fifteen thousand years. This is the end of the last Ice Age. The end of the Ice Age radically changed climates worldwide, submerged extensive coastal regions and caused extensive migrations of people. Its effects on India and Greater India were particularly important, devastating and transforming to the entire environment. These events form the basis of any real examination of the history of the region or of the history of humanity as a whole.
India's links with Greater India were even closer ten thousand years ago and earlier during the Ice Age period when the whole region – from peninsular India to Indonesia – formed at various times either a single landmass or a massive archipelago of islands and peninsulas separated by relatively shallow, easy to cross sea-lanes. This created a vast landmass known as 'Sunda Land'. Large areas of Sunda Land along with substantial strip of the Indian coast were submerged by rising sea levels when the last Ice Age ended. This has to be the natural background from which to begin any study of the history and culture of the Indian people. Their history cannot be set apart from these natural connections with Greater India and its populations. Nor can we ignore the impact of the cataclysms on the inhabitants of the region.
Sunda Land and South India, especially the coastal regions, were the most favorable places for populations. Since they both had abundant heat and moisture, throughout the Ice Age period, when much of the northern hemisphere was cold, arid and inhospitable. This may be reflected in South Indian recollections of Kanya Kumari, a larger Pacific continent to the South, and to Vedic references to the sea and early maritime cultures. It is also why the peoples of India and regions referred to as Greater India are genetically older and more diverse than those of Europe and West Asia. This is because these regions constitute a single natural zone united by geography, climate and natural history. In view of this unity which is of untold antiquity and is also reflected in the history and culture of the region, it is properly called Greater India. Modern terms like Indo-China and Indonesia are no more than recognitions of this historical fact.
When sea levels rose, it was these best habitable lands that were lost, triggering migrations to the interior and the north. This was probably the greatest and most consequential migration in human history that set in motion most of the cultures and changes to civilization that came later. It holds one of the keys to understanding the region's prehistory along with its chronology.