I don’t know if you like parties. I don’t know if you’re organized or punctual. But I bet you don’t like rotting smells or long swims in freezing water.

That is to say: People are different, but only in certain ways. What’s the difference? Hypothermia enthusiasts have few kids, so their genes tend to disappear. If introverts were worse at breeding than extraverts, then the same thing would have happened. Since extraversion varies widely, we can infer that we’re at an equilibrium point with no real advantage either way. (Personality traits are around 40% genetic.)

So, no personality is better than any other. Instead, there must be intricate tradeoffs, with each personality occupying a different kind of niche.

That’s what I thought, anyway. Then I read a few dozen papers and made this table:

This shows correlations between the Big Five personality traits and various personal characteristics. Blue shows positive correlations, while red shows negative. For example, the blue upper-left cell shows that extraversion is associated with life satisfaction, whereas the red lower-left cell shows that extraversion is negatively associated with autism.

So, uhh, where are the tradeoffs? People who are extroverted, agreeable, conscientious, emotionally stable, and open seem to do better at basically everything. Let’s call these people all-blues. Broadly speaking, they are more happy, successful, intelligent, creative, and popular. They have fewer addictions and less of every mental disorder. The only real tradeoffs are agreeableness against income/intelligence and extraversion/conscientiousness against math scores.

I’d like to give a list of famous all-blues as examples, but this doesn’t seem to exist. As a proxy, we can look to Myers-Briggs, where all-blues are similar to emotionally stable ENFJs. The internet claims that examples of ENFJs are Michael Jordan, Oprah, Pope John Paul II, Martin Luther King Jr., Pericles, and Barack Obama. For the opposite type, famous ISTPs supposedly include the Dalai Lama, Ernest Hemingway, Snoop Dogg, Melania Trump, and Vladimir Putin. (Personally, I assume the Dalai Lama has high emotional stability, but judge for thyself.)

Anyway, what’s the deal here? Why don’t we see more tradeoffs? Is the idea of a population equilibrium mistaken?

Evolution don’t care

Evolution doesn’t care if you’re happy. Evolution only wants you to pass on your genes. Berg et al. (2014) took data from 10.7k representative Americans born between 1900 and 1947 and did a regression to predict the number of grandchildren someone has from their personality traits. Here are the regression coefficients:

The personality characteristics are standardized so Extraversion = 0 for someone who is average, and Extraversion = -2 for someone 2 standard deviations below average, etc. They focus on grandchildren to reflect the influence of a parent’s personality on a child’s survival, but just using children gives similar results.

If you’re wondering, this suggests the ESFP as the most fecund MBTI type (Ronald Reagan, Bill Clinton, Hugh Hefner).

On the one hand, this would explain why everyone isn’t an all-blue: If you want to dominate the personality landscape, you need to reproduce more. On the other hand, it creates a bigger puzzle: If we were in population equilibrium, all the coefficients would be zero! Instead, there are huge effects like extroverted men having 0.8 more grandchildren than introverted men. If that’s true, then we are way out of equilibrium, and future generations will look different from us.

It’s tempting to make up post-hoc stories for those coefficients. (“High openness people spend too much time on rationalist-adjacent blogs,” har-har, yes, very good.) But it’s not that simple. You’ve got to do one of two things.

• You might reject the idea of a population equilibrium. If so, you should explain why the rules of natural selection do