That sounds wrong. Perhaps you're confusing frequency with likelihood?
IQ is standardised so that population scores on a standard test have a mean of 100 and standard deviation of 15. It's possible to obtain this with as fewer than 100 people, distributed as:
* One "genius" who scores 200
* One "dumbass" who scores 0
* 87 "everyman" who score 100.
The mean here is clearly 100, and the variance is sqrt(20000/89) = 14.99.
Of course this is very contrived and doesn't look much like a Bell curve in the first place. But with say a million people it wouldn't take much to come up with a more realistic looking example.
Matter of perspective; one in the 100~150 billion sapiens (or more) that have gone before and the rates go up. It's also possible rates are underestimated, as we have only tested a relatively small sample compared to N=all
If we test every living human, we can figure out who is the very smartest one. That person has a 1-in-<current_pop> intelligence, from which we can calculate their IQ. That IQ is nowhere near 200.
It would be handy to have standardized test answers from every human ever, but sadly most are dead as you point out.
A difference in 1 IQ point in the 100-101 range might be a difference in absolute problem-solving ability of x units, while than the difference between 170-171 is y units.
IQ is standardised so that population scores on a standard test have a mean of 100 and standard deviation of 15. It's possible to obtain this with as fewer than 100 people, distributed as:
* One "genius" who scores 200
* One "dumbass" who scores 0
* 87 "everyman" who score 100.
The mean here is clearly 100, and the variance is sqrt(20000/89) = 14.99.
Of course this is very contrived and doesn't look much like a Bell curve in the first place. But with say a million people it wouldn't take much to come up with a more realistic looking example.