were lost in mass extinctions. 在大规模灭绝中消失

163. At four different times,
     在四个不同的时期
164. the planet has pushed life to the very edge of existence.
     地球将生命推到了灭绝边缘
165. Each time, more than three-quarters of all species
     每一次 超过四分之三的物种
166. were lost in mass extinctions.
     在大规模灭绝中消失
167. Ours can be a brutal planet.
     我们的星球有时候很残酷
168. But there was one period
     但曾经有一个时期
169. when Earth was stable for 100 million years.
     地球保持了一亿年稳定状态

来自《我们星球上的生命 第一季 第一集 Life on Our Planet S01E01 生命法则》第 166 行