It still is for one person in four- 这仍旧是世界上四分之一的人类
It was a considerable leap in human history. 这是人类历史上质的飞跃
That abounded in fish, game and wild plants. 富有鱼 猎物及野生植物的环境中生活
They chose to live in wet environments... 他们选择了在湿润的
In the great adventure of life on earth, 在地球上生命的伟大冒险中
In perpetual movement toward the sky. 自然界元素
The earth counts time in billions of years. 地球以亿为单位计算时间