In two-thousand three, American William Ruddiman first proposed that global warming resulted from human activities thousands of years ago.

VOA: special.2011.04.26

And one of the reasons that's most responsible for that is that humans aren't dying at as young an age from infectious diseases as they did three or four hundred years ago.

最重要的一个原因就是,人们不会在年轻的时候死于传染性疾病,而这在三四百年前确实会发生

耶鲁公开课 - 生物医学工程探索课程节选

Padini Hajarin moved to the United States from Iran three years ago.

VOA: standard.2009.07.25