新托福阅读材料：Large-BrainedMammalsLiveLonger

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　一项最新研究表明，拥有更丰富智力的哺乳动物寿命更长。  
0 u; J4 b* v7 P' N　　A new study finds that mammals with larger brains—relative to body size—tend to live longer.

, t9 w2 R6 B6 t" r　　It’s been a question evolutionary biologists have spent years trying to answer: Why would nature favor the development of a large brain, something that requires more time to mature and uses up so much more energy? The classic thinking has been that large brains provide the sort of cognitive capacity needed to survive in an ever-changing environment, like the sudden loss of food or the appearance of a new predator.
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: V7 A9 E2 x3 h) G# |) b　　Now scientists have added a new factor to consider. Large-brained mammals live longer than those with smaller brains and so can not only have more chances to reproduce, but also have a longer reproductive cycle to allow more time for child rearing.

　　The team analysed nearly 500 species of mammals from across the globe, from bats to felines, ungulates and marsupials. And they found the correlation that indeed having a large brain makes for a longer life—the study was published this week in the Journal of Evolutionary Biology. The researchers analyzed other variables that could affect longevity like diet, environment, metabolic rates and found that the most significant predictor was brain size.

( X# S" ~; \3 K　　The authors stress, however, their finding is a correlation, and does not show causation. So on the one hand a larger brain favors a long lifespan but the opposite could also be true, that a longer lifespan favors a large brain.

1 z; a- L  R+ f. N0 O! `1 a# j　　In any event it seems size does matter, at least when it comes to grey matter.

　　—Christie Nicholson