古人如果活过了21岁，就大概率可以活到6，70岁。我在好几本

不同的书里都读到这个说法, 所以估计这个说法的可信度还行。

下面链接是几年前读到的印象特别深的一篇：

https://www.bbc.com/future/article/20181002-how-long-did-ancient-people-live-life-span-versus-longevity

From 1200 to 1745, 21-year-olds would reach an average age of anywhere between 62 and 70 years

 

The life span of humans – opposed to life expectancy, which is a statistical construct – hasn’t really changed much at all