Robin Dunbar is a professor of anthropology at the University of Oxford, a renowned evolutionary psychologist and author of Friends: Understanding the Power of Our Most Important Relationships.

Friendship is one of life’s simplest pleasures. While it’s easy to take friendships for granted, the variety of people in your corner often defines how balanced, supported, and joyful your life feels.

While everyone else is collecting friends like social media followers, psychology reveals that those who cherish just one or two deep connections possess a rare combination of emotional intelligence, ...