That's only if we take the Flynn effect at face value. No one does, because the implications are nonsense.

Go back in time and the average intelligence will be lower, but that's only because of a longer tail on the lower end of the distribution (the usual suspects: nutrition, lead poisoning, child abuse, iodine deficiency ...). On the smarter end, it's relatively unchanged because of diminishing returns.

The Flynn effect has many proposed, non mutually-exlusive causes, but an actual secular increase in real brain horsepower is not among the big ones.