Living through the climate changes that followed the end of the last ice age, these early colonists of the southern lands were forced to adapt to the new environments of lakes and woodlands. This process had already occurred with their Paleo-Indian predecessors at Monte Verde, but the extinction of the megafauna (very large land mammals) forced these groups to seek new subsistence methods. Somewhat later, around 5000 BCE, a new kind of adaptation centering on coastal resources gained force, providing the stability necessary to launch a transformation towards a more sedentary way of life, including the use of boats to colonize nearby islands. Around the first century of our era a new horticultural way of life began to emerge, now known as the Pitrén culture.