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This is Scientific Americans 60 second Science, I am Christopher Intagliata, got a minute?

You've probably had the feeling. Your running shoes are pounding the pavement—then suddenly your pain

fades away, and you're feeling euphoric. The runner's high. But that biological perk¹ may be limited to mammals that evolved for endurance exercise—like us. So says a study in the Journal of Experimental Biology.

Researchers had humans and dogs—both natural-born runners—jog a half hour on a treadmill². Then they sampled their blood for endocannabinoids, some of the compounds thought to trigger the runner's high. As expected, humans and dogs had much higher levels after the run. But when ferrets—a sedentary species—took the same 30-minute trot³, they had no spike⁴ in those feel-good molecules⁵.

The authors say that's because long-distance running could have helped our hunter-gatherer ancestors find more food—thus increasing their reproductive success. And they speculate that natural selection may have linked up a feel-good reward to that beneficial behavior. These days of course, this ancient trait won't help us find extra calories—but it may encourage us to run 'em off.

Thanks for the minute for Scientific Americans 60 second Science, I am Christopher Intagliata

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1 perk
n.额外津贴；赏钱；小费；
参考例句：
His perks include a car provided by the firm.他的额外津贴包括公司提供的一辆汽车。 And the money is,of course,a perk.当然钱是额外津贴。

2 treadmill
n.踏车；单调的工作
参考例句：
The treadmill has a heart rate monitor.跑步机上有个脉搏监视器。 Drugs remove man from the treadmill of routine.药物可以使人摆脱日常单调的工作带来的疲劳。

3 trot
n.疾走，慢跑；n.老太婆；现成译本；(复数）trots:腹泻（与the 连用）；v.小跑，快步走，赶紧
参考例句：
They passed me at a trot.他们从我身边快步走过。 The horse broke into a brisk trot.马突然快步小跑起来。

4 spike
n.长钉，钉鞋；v.以大钉钉牢，使...失效
参考例句：
The spike pierced the receipts and held them in order.那个钉子穿过那些收据并使之按顺序排列。 They'll do anything to spike the guns of the opposition.他们会使出各种手段来挫败对手。

5 molecules
分子( molecule的名词复数 )
参考例句：
The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。 Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。