For many years, one way or another, I have been stumbling back to an interesting and funny article: What is the Monkeyspehere by David Wong on cracked.com.
Essentially the article explores the limit of people we can care about. This “Monkeysphere”, cited as about 150, is the rough maximum number of people we can have in our lives who we can genuinely emphasise with.
This is due to how we are built – specifically, the genetics we have inherited from our monkey ancestors which help them survive.
For me, the theory explains a lot, and I can’t begin to do it justice here… but recently, I found that the article is based on a more academic notion known as Dunbar’s Number.
The Monkeyspehere article is well worth a read (if anything, it is funny) and the concept can be explored further via Dunbar’s Number.