即使一种行为模式是近乎普世的，我们也无法预先知道它究竟是一个我们不能改变的自然法则，还是只是一种我们能够并且应该改变的原始陋习。
Even if a pattern of behaviour is almost universal, we can't know in advance if it is a law of nature we cannot change or simply a remnant of our primitive past that we can and should modify.
不过，事实仍然是，仅仅改变氧气浓度一项指标，蜻蜓的体型就自然增大了。 遗憾的是，我们不能把这些巨型蜻蜓放到野外去对付那些致人死命的蚊子。
Still, the fact remains that a simple change in oxygen levels produced naturally giant dragonflies--too bad we can't release them into the wild to take care of those deadly mosquitoes .
“如果你尝试着去改变你的自然的机体节律，我们不能完美的适应那样，”南希—克罗博士——埃默里临床睡眠混乱中心的主管说。
"If you're trying to alter your natural body rhythm, we don't adjust perfectly to that," said Dr. Nancy Collop, director of Emory Clinic Sleep Disorders Center.
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