Humans could increase their ecological footprint by domesticating the plants and animals that they found useful. They learned how to change these organisms by means of selective breeding – an early and effective form of genetic engineering. In this way, humans created new environmental niches for themselves that came to be known as agriculture and animal husbandry.

As human environmental manipulation in the Triangle reached a higher level, it began to take on many new characteristics. Older subsistence strategies based on hunting and gathering food strongly persisted, as did the mobile groups of people that typified this lifestyle. But they were now joined by groups that settled more permanently to practise specific forms of agriculture and animal husbandry. These forms largely depended on the terrain, much of which was mountainous, and the generous monsoon climate. Three broad types of Triangle livelihood began to take shape – and they survive today.

High-altitude life: Transhumance

The northern reaches of the Triangle include some of the highest elevations on earth. Here humans faced many problems of survival. In the high valleys on the southern face of the Himalayas, glaciers meet the wet South Asian monsoon, however, and here permanent human habitation was possible from at least 2500 BCE. Thanks to greater control of animals and plants, a specific lifestyle took shape.

This lifestyle depended on the domestication of two high-altitude species: a bovine and a grass. Once humans were able to control and exploit the yak and barley, they knew how to survive just below the glaciers. The yak is a wild bovine that is perfectly suited to high altitudes. Current evidence suggests that yaks were first domesticated around 5000 BCE. Today fragmented populations of wild yaks can still be found on the Tibetan Plateau but not on the eastern Himalayas. Here yaks were domesticates that became essential to human survival (Plate 4.1). It is thought that the first settlers of these alpine valleys came from the Tibetan Plateau and used fire to clear some of the natural vegetation of rhododendrons and junipers. They used the land to graze yaks (and possibly sheep) and to grow barley during the summer months. The ecological impact of grazing was distinct: some plants species were marginalised, and others flourished.