evolution didn't make giraffes tall. it made giraffes a bell curve, normal distribution of various heights.

then for thousands of years, millions and millions of the unlucky short ones starved to death, emaciated ribs poking out, before they could reproduce. gradually the center of the bell curve shifted right.

1600/day are dying of covid in the usa, while vaccines that almost entirely prevent death are widely available for free.

it's the same for intelligence. it takes a long time.