But as the environment became drier around two million years ago, they began to forage in more-open grasslands-a problem for brains, which are notoriously vulnerable to heat.

但200万年前，随着环境变得更加干燥，他们开始在更开阔的草地上寻找食物——这对大脑是一大考验。众所周知，大脑对热很敏感。

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The cheetah finds the open grasslands ideal footing for its lightning-quick sprints.

非洲猎豹把开阔的草原作为它们闪电猎食的理想处所。

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Cattlemen would send out cowboys to search the open grasslands for their animals.

VOA: special.2010.03.18

Mr Scheiman blames the loss of open spaces and grasslands for the drop.

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Researchers Russell Ciochon and E Arthur Bettis III, from the University of Iowa, US, believe these climatic cycles may have caused the expansion of open habitats, such as grasslands and steppe.

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The modern freeways and suburban sprawl give way to high grasslands in the Sierra Azul Open Space Preserve and dense redwood forests north of Santa Cruz.

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