[kouru225]

I think this is actually an easy question to answer because you’ve accidentally preselected your demographics.

Imagine this: among primates, there is an even distribution of species of differing levels of intelligence. All the primates who became intelligent have similar evolution paths because intelligence defines their evolution path (opposable thumbs, large heads, standing upright, etc.) Then because they all have similar evolution paths we put all those into the genus “Homo.” Each of species of the genus Homo eventually either breeds with each other or genocides one another until there are only the Homo Sapiens left.

So with an even distribution of intelligence among all primates, it’s logical that, given enough time, all that is left are primates of sufficient intelligence enough to breed with each other or be genocided until there is only one species, or many species of primates who weren’t intelligent enough.

This is my guess (I’m not a biologist or ancient historian or anything)