The world population reached 8 billion. It has grown by 2 billion since 1998. That's the year that my older child was born. Of the 2 billion people who arrived on this planet in the last 24 years, there are only two that I really care about. That's a small percentage. Sure, I care about people, but it is curious to consider these two humans as part of a 2 billion person cohort with little in common other than a time period of birth.