万年前

• The creature was about 20 feet long and lived 78 million years ago
  该恐龙的体长约为20英尺（ 6 . 1米）左右，其生活年代则在距今7800万年前。
• A lake that formed about 400 , 000 years ago , and famous for not freezing all year round
  大约在40万年前形成的湖泊，以全年不冻湖而闻名。
• By about 16 million years ago in the rock record , the red and white sediments disappear
  到了1600万年前，岩石记录中的红色及白色沉积物消失。
• Around 70 , 000 years ago its last eruption filled in that gaping hole with flows of lava
  大约7万年前，最后一次火山爆发，熔岩流填满了许多洞穴。
• They call 55 - million - year - old diatryma gigantean a terror bird . and the evidence is compelling
  人们把这种生活在5500万年前的大鸟称作恐怖鸟。是很有道理的。
• The fourfold expansion of the hominid brain started 2 . 5 million years ago , when the ice ages began
  人猿类的脑扩增四倍，开始于250万年前，也就是上一次冰期之初。
• Paleontologists had thought that grass evolved well after dinosaurs died out 65 million years ago
  古生物学家一直以为，禾草是在6500万年前恐龙已完全消失后演化出来的。
• Scientists say that the primitive tools found in the cave were used by humans about 10 , 000 years ago
  科学家指出，在此洞穴发现的原始器具，是一万年前的人类所使用的工具。
• It ' s similar to the brain possessed by the hardy reptiles that preceded mammals , roughly 200 million years ago
  这类似脑被先于大致2000万年前的哺乳动物坚硬的爬虫动物支配。
• But globalisation really began about 60 , 000 years ago , when the first migrants walked out of africa
  但是，全球化真正出现的时候是六万年前，那是第一批非洲移民走出非洲大地。