There are a lot of numbers in my life. There are telephone numbers, of course, a few of which I still have accidentally memorized even though there’s no reason to waste my brain juices on that kind of thing anymore. I’ve got credit card numbers, bank account numbers, height, weight, age, cholesterol (is it still supposed to be below 200 or is that a relic from my childhood?), BMI, the current mortgage interest rate, the payoff balance on my car, the legal blood alcohol level, the number of pairs of underwear my brother has (long story, but it was a bet, and the answer turned out to be significantly less than his wife’s collection but more than he thought it would be), the number of representatives to the House and Senate, the exact number of π (I still know it’s 3.141592 and that’s where I stop), and probably several dozen more. And my guess is that when it comes to numbers, you’re a lot like me.
However, there’s one number you very possibly don’t know, and it’s the most important number I’ve run across in the last few years – 150, which is also known as Dunbar’s number. I know some of you have read my most recent book, so I’ll summarize this as quickly as possible. Dunbar’s number is a scientific estimate of the number of other human beings that any one of us can actively care about at any given time. The actual number will of course vary from person to person, but the point is this: if there is a physical limit to how tall or fast or strong a human being can become, it follows that there should also be a neurological limit to how many interpersonal relationships we’re able to maintain all at once.
Why is this important? Because recognizing that we have a finite capacity for community is absolutely the best (and possibly the only) way to keep ourselves from getting in over our heads. All the anecdotal evidence I’ve been able to gather suggests that most of us feel like we’re working harder all the time for increasingly diminishing returns. The whole point of building machines is to make the world easier or more comfortable than it was before, and in almost every case this is true – I am able to write this much faster on my computer than if I had to scribble it with a piece of chalk or a quill pen. But when it comes to the social side of things, technology’s erasure of the barriers that once kept us apart seems to have made life feel more complicated than it was before. There’s always another story to read, another picture to post, another “How have you been?” from another long-lost friend that requires a response. In our quest to bring the world to our fingertips, many of us have found that we’re inadvertently serving too many masters.
That’s where Dunbar’s number comes in. If you’ve ever felt overwhelmed with the weight of all your obligations and the number of people you feel beholden to, it could be that you’re bad at multitasking; but it’s far more likely that you’re stretching your brain beyond its neurological boundaries. If you castigate yourself for being unable to handle everything, it’s largely because you haven’t honestly acknowledged that your brain is not a perpetual motion machine. And if you’ve ever felt like you’re forever falling short against the endless competitors the modern world is constantly throwing up against you, the reason is very likely because you are comparing yourself against more people than your brain has the ability to properly process. The better you are at tuning out those parts of the world you aren’t directly involved in (which mostly means becoming more selective with how much technology you invite into your daily life), the better you will feel about yourself. This isn’t the idle opinion of a guy who thinks Facebook is sort of annoying; this is a truth rooted in the hardwiring of the biological machine that governs everything we are and do.
Our brains are incredible, and they’ve come up with some truly awe-inspiring creations (not the least of which is the fact that ‘pumpkin spice’ has managed to find its way into 4,987 products). But for all their power, our brains are still machines, with the same limitations that all machines have. The phrase I’m supposed to use here is “we forget this at our peril,” but I don’t think that’s the right way to put it. We forget it at the expense of our happiness.