KEY POINTS

Humans can maintain only so many friendships effectively.

Relationships significantly influence mental and physical health.

Friendships can shift based on interactions and time spent together.

You may have 11 million followers on social media and an extended network of colleagues and acquaintances. But a British evolutionary psychologist and expert on primate behavior became famous for deciding the upper limit of how many friends the human primate brain can handle.

It’s called the “Robin Dunbar Theory” or “Dunbar’s Number” or even the “social brain hypothesis,” first proposed decades ago, and it’s still being wildly debated.

Dunbar, now in his late 70s, told The Wall Street Journal this week that when you get beyond 150 friends, they become “one-way” relationships. “The

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