Can you imagine a way to measure intelligence that doesn't involve sitting down to take a test?
In many ways, we measure intelligence when we look at someone's accomplishments, awards, credentials, and so on. It doesn't take an official IQ number for us to know that a Nobel Prize winner or a hoodie-wearing tech CEO is no dummy.
The underlying quantity we are measuring? Effect.
I propose that the sum of a person's effect on their environment (which is mostly other people) is the measure of their intelligence.
Think of each person as having mass: the larger a person's mass, the more effect they have, and thus the more intelligent they are. It works exactly like the relationship between physical mass and gravity.
Effect is a behavior of yours which changes another person's behavior. The more people you reach, and the more you changed their behavior, the higher the measure of your effect. A societal shift like the spread of a religion such as Christianity, Hinduism, Buddhism, or Islam, the spread of an idea like Darwin's Natural Selection or Einstein's General Relativity, or a transcendent work of art like the Mona Lisa produces a significant behavioral shift across a wide population over a long period of time. That's galactic-scale mass. In contrast, the total effect of a typical person living their typical life is closer to the microscopic scale.
One way we measure effect is through Likes or Shares on social media. Other ways are websites hits, total sales, butts in seats, bank account balances, numbers of friends, and viewership numbers. If you look closely, you'll notice thousands of different ways each of us continually measure both our own effect and the effect that others are having.
All day, every day, we're each measuring our intelligence and comparing it to our old self, to others living, and to others past. If we're feeling good about ourselves, our total mass is probably growing more than usual. If we're feeling bad about ourselves, our total mass is growing less than usual. You might be surprised how closely your emotions are tied to the fluctuations of your mass (your summed effect).
The good news is that this measure of intelligence is neither fixed nor bounded. You could go from zero to worldwide hero if you play your cards just right and get the right kind of luck.
The bad news is that everyone will know you're a dumbass because you'd rather play videogames all day.