Polygamy marriages should be greatly encouraged and supported

1 man can make 5 women pregnant, so 20% of men can make all women pregnant.

So smartest 20% to 30% of men reproducing with all women would create best and smartest offspring.

Now, about early marriages. I know its not the topic, but who cares.

Woman can give birth to greater number of children if she starts giving birth earlier. This helps all countries with low birth rates, and many countries have birth rates below replacement levels.

The "age of reasonable safety" still presents significant risks to both mother and child in developing countries world also the age of "reasonable safety" is between your late 20s and early 30s. This contradicts your initial argument for early marriage to maximize births.

I would like to add that Intelligence is mostly unrelated to genetics but instead, the environment the child was raised in. Do women have a choice in reproductive partners? If not, what prevents coercion, violence, and population decline, directly contradicting your point of increasing the population?

Also, who decides the top males, and who would raise the kids what if the man or women decide they don't want to raise the child than what? Or what if a woman decides that she doesn't want to have kids, would you force her to have them?

Lastly, you have yet to provide an objective, measurable definition of "best offspring". Until a clear and quantifiable metric is established, this claim remains impossible to debate.




Sources: 
https://www.healthline.com/health/womens-health/childbearing-age
https://pubmed.ncbi.nlm.nih.gov/11447922/