However, scientists previously thought, HIV from the body chimpanzee SIV.

不过，科学家先前认为，HIV源于黑猩猩身上的SIV。

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Our planet's risk of being hit by a dangerous outer space rock may be smaller than scientists previously thought.

我们这颗星球被太空小行星(陨石)击中的危险可能比科学家以前估计的更小一些。

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Previously it was thought there were around 100, 000 microbial cells in every litre of seawater but scientists now think there could be one billion.

在此前的推测中，每一升海水中可能会有大约10万个微生物细胞，但现在科学家们认为有可能达到10亿个。

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Seagrass beds in Loch Gairloch and Gruinard Bay were more widespread than previously thought and scientists think the beds are possibly the richest examples in north Scottish waters.

BBC: Exploration around Ullapool confirms important species

Weeks after Superstorm Sandy, scientists are now predicting the near-term and long-term effects of global warming as more dire that previously thought.

CNN: The Maya collapsed - could we?