Twenty thousand years ago, as the world's climate begins slowly to warm

Twenty thousand years ago, as the world's climate begins slowly to warm after the last major glaciation, and Asian peoples cross—or continue to cross—the Bering Strait between Siberia and Alaska, these new Americans spread out through the two large continents. Reaching temperate environments, they begin to diversify. While continuing to hunt game for food, they also gather edible plants and shellfish. Shelter is found in caves or rocky outcroppings, or built in tentlike structures of wood and animal skin. Weapons and tools are fashioned from wood, stone, and bone. Cordage, netting, and basketry develop and fiber-tempered pottery is eventually fired. The practice of placing significant burials beneath earth-and-stone mounds is initiated.