The average life span of humans continues to lengthen, and some scientists have begun to ponder whether this trend will continue indefinitely.

随着物质生活的不断提高，人类的平均寿命有不断变长的趋势。一些科学家们也开始仔细思考这个趋势是否会一直持续下去帮助人类达到永生。

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Compare this with an average life span of 52 in 1960, or of about 30 in 1900.

把这个数字与1960年的平均寿命52岁相比，又或者与1900年的人均30岁寿命相比。

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The tiny European nation of San Marino boasts the longest average life span for men, with 81 years.

欧洲小国圣马力诺则成为男性平均寿命最长的国家，为81岁。

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There is a high mortality rate -- with an average life span of only 47 -- minimal infrastructure and limited tools for economic development.

CNN: Commentary: A week with the heroes

This was the first fall in a decade and dashed hopes that the life span of the average Russian would beat the Gorbachev-era peak and exceed 70 years for the first time ever.

WSJ: A Lost Opportunity to Save Russia

If the SenesTech taste test proves successful and birth-control bait is used throughout the transit system, the average life span of subway rats which now tops out at about one year, according to Mr. Lamb would probably rise slightly even as the total population declines.

WSJ: MTA Sets New Tactic in Rat War