age在这个句子里是时代、世纪的意思,即a particular period of history,一般用单数
in the age为固定搭配,意思为在.时代
We are said to be living in the age of information now.据说我们现在生活在电脑时代.
在朗文现代高级英语辞典中也有句子We are living in the computer age.