1. Low average population densities are characteristics of most underdeveloped countries. 平均人口密度低是大多数不发达国家的特点。
2. As densities increased, domestic architecture became larger, culminating in crowded pueblos. 随着密度的增加，住宅建筑变得更大，最终形成拥挤的村庄。
3. The cultivation of crops has expanded into progressively drier regions as population densities have grown. 随着人口密度的增长，农作物的种植已经扩展到了越来越干旱的地区。
4. Rock lobsters prey on sea urchins, and increased rock lobster densities coincided with significant decreases in urchins. 岩石龙虾以海胆为食，而岩石龙虾密度的增加正好与海胆数量的显著减少相吻合。
5. After several generations of population growth, people packed the landscape in densities so high that communal pueblos may have been a necessary outcome. 经过几代人的人口增长，人们以如此高的密度挤满了这个地区，以至于公共聚居地的出现可能是一个必要的结果。
