Until mankind's big expansion some 500 years ago, mammal extinctions were very rare: on average, just two species died out every million years.

在人类从500年前开始大扩张之前，哺乳动物的灭绝十分罕见，平均每一百万年只有两种灭绝。

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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。

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But some farmers used toxic additives as early as 4, 500 years ago, when Sumerians dusted crops with sulphur to kill insects.

然而早在约4500年以前，也有农民使用有毒的添加剂，苏美尔人便将硫磺撒在作物表面以杀死虫子。

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His Y chromosome was traced back to the Middle East, possibly an indication of a Jewish ancestor among the many escaping persecution in Portugal and Spain some 500 years ago.

BBC: The BBC project analysed the DNA of nine famous Brazilians

The researchers determined that the jawbone came from a man aged between 24 and 30 years who lived some 6, 500 years ago.

UNESCO: Basic Sciences

The academics suggested that Stonehenge was built about 200 years earlier than previously thought, some 4, 500 years ago.

BBC: Stonehenge builders travelled from far, say researchers