Alright.

We can use statistics, we can use socio-economic studies, we can even ask people on the street. Stats, you can pick ANY developed region or country in the world and compare. I can guarantee you, that there isnt developed place where atheists would be atleast able to replace their own population (2.1 children per woman), fertility differences within groups of same socio-economic standing largely reflects how much individuals of said groups rely on faith and moral compass that comes with it. Nominal income or race cannnot explain difference in the rates of reproduction.

Your description of evolutionary process is correct. Stronger thrive and pass on genetic information, while the weak remove themselves from the gene pool. It can and is aswell used to evaluate cultures, private bussiness and ideologies.

What if absense of faith is a sign of weakness putting its adherents at vast disadvantage?

Mr. Kaufmann, author of the article is professor of politology at University of London. Hardly someone we could call religious fundamentalist.

https://www.prospectmagazine.co.uk/magazine/breedingforgod