The rates of extinction happening today are as great as the rates during these mass extinctions.
现今物种灭绝发生的速度和这些大规模灭绝的速度一样快。
Airborne soot and dirt from the impact blanketed Earth, inhibiting photosynthesis and triggering mass extinction of species.
撞击产生的烟尘和灰尘覆盖了地球，抑制了光合作用，引发了物种的大规模灭绝。
This break in Earth's history is marked by a mass extinction, when as many as half the species on the planet became extinct.
地球历史上的这次重大灾难以物种的大量消亡为标志；当时，地球上多达一半的物种都灭绝了。
Following each mass extinction, there is a sudden evolutionary burst as new species develop to fill the ecological niches opened by the event.
在每一次物种大灭绝后，都有一次突然的进化爆发，因为会有新物种出现来填补灭绝创造的生态位。
If you think about it though, the core problem with this sixth mass extinction is human interference.
如果你仔细想想，这第六次大灭绝的核心问题是人类的干扰。
As Permian life-forms declined, they reached a fatal threshold and species succumbed to mass extinction.
随着二叠纪生命形式的衰退，它们达到了一个致命的临界点，物种最终走向了大灭绝。
Scientists have linked the mass extinction at the end of the Cretaceous with a meteorite impact on Earth.
科学家将白垩纪末期的大灭绝与地球上的陨石撞击联系起来。
Evidence points to hunting by humans and habitat destruction as the likely causes for the current mass extinction.
有证据表明，人类的捕猎和栖息地的破坏可能是导致当前物种大量灭绝的原因。
Presumably, those environmental disasters could have been responsible for the mass extinction, including the death of the dinosaurs.
据推测，这些环境灾难可能是物种大规模灭绝的成因，包括恐龙的灭绝。
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。
Today we are witnessing a sixth mass extinction, but unlike the others, the current loss of bio-diversity can be traced to human activity.
今天，我们正在见证第六次物种大灭绝，但与其它几次不同的是，目前生物多样性的丧失可以追溯到人类活动。
First, that there was not one mass extinction at the end of the Permian, but several.
第一，在二叠纪结束的时候并不是一个大规模灭绝，而是好几个。
This marks precisely—to within a few thousand years—the point of mass extinction on the land.
这明确标志着正是在这几千年中，发生了陆地上的大规模灭绝。
Of course, humanity is currently setting off the sixth mass extinction event in Earth's history.
当然，人类正在引发地球历史上第6次物种大灭绝。
Permian-Triassic The worst mass extinction took place 250m years ago, killing 95% of all species.
二叠纪-三叠纪最严重的大灭绝发生在两亿五千万年以前，杀死了所有物种的95%。
In this movie, a comet miles across is headed toward Earth, sure to cause a mass extinction if it hits.
在这部影片里，以颗直径几英里的彗星直奔地球而来，一旦撞上，就会是天崩地裂的大灾难。
None of it lines up to say a mass extinction and there is very little evidence to say humans drove the extinction.
没有一个数据指出曾有一次大规模的灭绝，而且很少有证据说是人类导致它们的灭绝。
The Permian period, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago.
二叠纪开始于2.99亿年前，并以地球上最大规模的物种灭绝而结束。
Fossil evidence suggests that small and medium sized animals were more likely to survive the mass extinction than larger species.
化石证据显示，中小型动物比较大型物种更有可能在大灭绝中幸存下来。
When Grasby and his team analyzed rocks from just before the Permian mass extinction, they noticed unusual microscopic particles.
当Grasby和他的团队分析了“二叠纪灭绝”前的岩石成分后，他们注意到一些不寻常的微观颗粒。
However, some researchers believe that a GRB was responsible for the Ordovician mass extinction approximately 450 million years ago.
然而，有一些研究者认为，大约4.5亿年前的奥陶纪大灭绝是伽马射线爆引起的。
Australian scientists fear the planet is on the brink of another mass extinction as ocean dead zones continue to grow in size and number.
澳大利亚科学家担心，随着海洋死区范围和数量不断加大，地球已到了另一次大灭绝的边缘。
Tiny particles embedded in ancient Canadian rocks have provided new clues about what might have triggered Earth's deadliest mass extinction.
嵌入加拿大古代岩石的微粒为引发地球大灭绝的原因提供了新的线索。
Dinosaurs' high level of fitness could also explain why mammals remained so small until the mass extinction of the dinosaurs 65 million years ago.
恐龙的高度适应性可能也解释了为什么哺乳动物的体型总是那么小，这种情况一直持续到六千五百万年前恐龙大规模灭绝。
One fragment of that ancient smash is thought to have struck Earth 65 million years ago, triggering a mass extinction that wiped out the dinosaurs.
据认为，那次古老冲撞的碎片在六千五百万年前曾经撞击地球，引发了消灭恐龙的大灭绝。
It is also time to take stock, though. Human activities are causing a mass extinction, but the right action now could pull life back from the brink.
虽然现在是时候该算算账了，人类确实让很多物种濒临灭绝，但是我们也已经采取措施将濒临灭绝的物种从消失的边缘救了回来。
Otherwise, "one neat thing about mass extinction events is that they're often reset buttons, where you change what dominates the globe, " Conrad said.
从另一个角度看，“巧妙之处在于，大灭绝事件就像重启按钮，通过它可以改变主宰地球的物种，”Conrad 说。
Otherwise, "one neat thing about mass extinction events is that they're often reset buttons, where you change what dominates the globe, " Conrad said.
从另一个角度看，“巧妙之处在于，大灭绝事件就像重启按钮，通过它可以改变主宰地球的物种，”Conrad 说。
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