Over 40,000 years ago, a new species drifted into the Triangle, and it would change life here forever. This invasive species was an intelligent ape. It calls itself Homo sapiens, or (modern) human being. It was not the first member of the Homo family in Asia: a pre-modern cousin (Homo erectus) had arrived long before. Evidence of its presence has been found relatively close to the Triangle – in Yuanmou (southwestern China) and in the Kyaw and Upper Ayeyarwadi valleys (Myanmar) – but not yet in the Triangle itself.

We know little about the beginnings of modern human life in the Triangle because early Homo sapiens left few traces, and remarkably little scholarly research has been done into their whereabouts and lifestyles in this region. Generally speaking, the ‘archaeology of northeastern India, the Indo-Burmese borderlands, Burma and the northern Bay of Bengal littoral is virtually unresearched’. This means that archaeological assumptions about the region are rarely backed up by evidence – and yet it is, of course, important to be aware that ‘the absence of evidence does not constitute the evidence of absence’.

Luckily, striking advances in fossil, climate and genetic studies are beginning to give us more clues about the distribution and migrations of these earliest modern humans. New findings lend support to the ‘sub-Himalayan route’ thesis. This is the idea that the peopling of Southeast and East Asia (and ultimately the Americas and Australia5) owes much to eastward overland migration out of Africa. According to this theory, modern humans dispersed in the regions south of the Himalayas, perhaps as early as 100,000 years ago, and gradually gravitated further east. On the way, they may have interbred to some extent with other branches of the Homo family, now extinct, just as in westerly parts of Eurasia modern humans interbred with Neanderthals. Eventually, groups of modern humans entered the relatively narrow corridor between the Himalayas and the Bay of Bengal – in other words, the Triangle. Some settled there and others pushed on across the Indo-Burma Arc into what we now call Southeast Asia and East Asia.

This sub-Himalayan thesis qualifies two earlier assumptions about the earliest dispersal of Homo sapiens in Asia. The first is that East Asians descend from groups of humans that moved from Africa to central Asia and crossed the steppes north of the Tibetan Plateau.