Circling almost the entire Northern Hemisphere, 围绕几乎整个北半球

51. But south of the ice sheets,
    但是在冰层以南
52. a new world was created
    一个新世界诞生了
53. where life could thrive.
    生命在这里兴旺发展
54. Circling almost the entire Northern Hemisphere,
    围绕几乎整个北半球
55. the tundra-steppe became Earth's most extensive habitat.
    冻原成为地球上最广阔的栖息地
56. Mammals that adapted well to the cold dominated these frigid lands...
    适应了寒冷的哺乳动物 主宰着这冰雪天地
57. including the largest and most iconic of them all...
    包括其中最大、最具代表性的…

来自《我们星球上的生命 第一季 第八集 Life on Our Planet S01E08 冰与火的世纪》第 54 行