Recent data is in line with my opinion: they mature less and are less dimorphic, and as such their intelligence advantage does not continue to scale like ours with age. In other words, they have a youth advantage. But it does not persist. Meanwhile, we keep getting ‘smarter’ by about a point every three years. I suspect this is due to differences in the advantage of verbal ability, and also explains why the Ashkenazim retain that advantage throughout life. Again, mathematics and spatial reasoning are a form of calculation, but so is language.
And keeping them in relation (europeans) is something that the Ashkenazim do not do (like all Semites verbalism seems to be endemically ideal), and the east Asians have a huge population to draw from and their need for order helps their bureaucracies evolve into talent pools.
So again neoteny, rate of maturity, gender differences in brain development are the primary differentiators in human groups (species).
our only problem is rates of reproduction of our classes reversing our many centuries of eugenics.