But 20th century medicine did little to increase the natural life-span of healthy humans.

然而，20世纪的医学对健康人的自然生命周期的增长几乎无能为力。

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Such of words, ignore to die in what circumstance, the eyes power of god of also just it original natural life span.

这样的话，不管死于什么情况，死神眼看到的也只是其原本的自然寿命。

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The process of aging and eventual death must finally be taken as the natural process of the life cycle, the old completing their limited life span and making way for the young.

人们必须接受衰老及最终辞世是人生周期的自然进程，老年人结束自己的寿命，为年轻人让位。

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Sceptics point out that if big cats have been surviving, and breeding, in the wild for all this time, they only have a natural life span of some 20 years.

BBC: The Surrey puma: Fact or fiction?

But bacteria and viruses breed fast, so natural selection has time, within the span of a human life, to make a difference.

ECONOMIST: Evolution: Beetle drive | The

Scientists have long speculated that the key to a person's "natural" life span lies in so-called diseases of aging, those that emerge only as the body begins to wear out.

WSJ: A Gene Gives a Hint Of How Long a Person Might Hope to Live