When plants first made the transition ashore more than 400 million years ago, the land was barren and desolate, inhospitable to life.
4亿多年前，植物第一次向海岸上迁移时，陆地上荒凉而贫瘠，并非生命宜居之地。
Eighty million years ago, dinosaurs ruled the earth.
八千万年前，地球是恐龙的天下。
South America and Africa separated 200 million years ago.
南美洲和非洲于2亿年前分离。
South America separated from Africa 200 million years ago.
2亿年前南美洲和非洲分离。
Twenty million years ago, Idaho was populated by dense primordial forest.
两千万年前，爱达荷州遍布着茂密的原始森林。
It has been suggested that mammals took over from dinosaurs 65 million years ago.
有人提出哺乳动物是在6 500万年前取代恐龙的。
Twenty million years ago, Idaho was not the arid place it is now. Rather, it was warm and damp, populated by dense primordial forest.
2000万年前，爱达荷州不像现在这样干旱。确切地说，它那时温暖潮湿，生长着茂密的原始森林。
Some scientists believe that the first plants to appear on Earth over 500 million years ago probably looked purple, not green.
一些科学家认为，5亿年前出现在地球上的第一批植物可能看起来是紫色的，而不是绿色的。
A million years ago, we were essentially an endangered species.
一百万年前，我们基本上是濒临灭绝的物种。
It is said that dinosaurs were living in 200 million years ago.
据说恐龙是生存在200万年前。
Wild carrots probably evolved with the other flowering plants about 360 million years ago.
在大约3.6亿年前，野生胡萝卜也许是和其它开花植物一起进化的。
Ant societies existed in something like their present form more than seventy million years ago.
蚂蚁社会大约在七千万年前就以类似现在的形式存在。
Whales originated in the freshwater lakes and rivers of ancient Asia about sixty million years ago.
鲸鱼起源于大约六千万年前亚洲的淡水湖泊和河流。
In some parts of the world you can still find tools that people used more than two million years ago.
在世界的某些地方，你仍然可以找到两百多万年前人们使用的工具。
This gigantic boa constrictor, like a snake, lived 60 million years ago in what is now northern Colombia.
6千万年前，这种类似于蟒的巨蛇生活在现在的哥伦比亚北部。
We knew that it was formed from sandstone that solidified somewhere between 150 and 300 million years ago.
我们知道它是由1.5亿到3亿年前在某地固化的砂岩形成的。
About 160 million years ago, a female pterosaur with an injured wing dropped from the sky into a watery grave.
约一亿六千万年前，一只雌性翼龙隐翅膀受伤而坠落，葬身水底。
The split between humans and living apes is thought by some scholars to have occurred 15 to 20 million years ago.
一些学者认为人类和猿的分化出现在一千五百万到两千万年前。
A handful of Africa's unique island mammal families that were present 26 million years ago are absent from sites younger than Mush.
在比 Mush更年轻的遗址中，不少2600万年前只属于非洲大陆的哺乳科动物消失了。
Roughly 250 million years ago, in the worst series of mass extinction in Earth's history, almost all species of life simply vanished.
大约2.5亿年前，在地球历史上最严重的一系列大灭绝中，几乎所有的生命物种都消失了。
Fifty-seven feet long and up to nine tons, spinosaurus started poking his head around the early Cretaceous some 100 million years ago.
57英尺长，9吨重，棘龙在大约1亿年前的白垩纪早期就开始四处活动。
When the Hawaiian Islands emerged from the sea as volcanoes, starting about five million years ago, they were far removed from other landmasses.
当夏威夷群岛从大约500万年前开始以火山的形式出现在海面上时，它们远离其他陆地板块。
The earliest humans arrived several million years ago, but only 150,000 to 200,000 years ago, did cultures, language, religion and the arts arise.
人类最早出现在几百万年前，但直到15万到20万年前，才出现了文化、语言、宗教和艺术。
An iridium-enriched sediment layer and a large impact crater in the Yucatn provide evidence that a large meteorite struck Earth about 65 million years ago.
尤卡坦半岛上富含铱的沉积层和一个巨大的陨石坑提供了证据，证明了约6500万年前，一颗大型陨石撞击了地球。
About 400 million years ago, when the present-day continents of North America and Europe were joined, the Caledonian mountain chain was the same size as the modern Himalayas.
现在的北美大陆和欧洲大陆大约在40亿年前是连接在一起的，在那时，加勒多尼亚山脉与现代的喜马拉雅山脉一样雄伟。
Scientists have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago.
科学家们已经确定，在埃塞俄比亚阿法尔地区干燥河床的细颗粒沉积物中发现的具有锋利边缘的石片存在于252万至260万年前。
Quartz is quartz—a silicon ion surrounded by four oxygen ions—there's no difference at all between two-million-year-old Pleistocene quartz and Cambrian quartz created over 500 million years ago.
石英是石英——由四个氧离子围绕的硅离子——200万年前的更新世石英和5亿年前的寒武纪石英之间没有任何区别。
They were formed only 100 million years ago.
它们仅仅是在1亿年以前形成的。
They are of dinosaurs living 70 to 85 million years ago.
这些恐龙生活在7000万至8500万年前。
Up until about 3 million years ago, we were covered with it.
3百万年前，我们都是披着满身毛的。
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