Can't access article but I do think most people have kids because they think it's the 'done' thing. I think anyone who cares deeply about the planet or thinks a lot about the state of the world probably is more reluctant to have kids as we are heading towards climate change disaster and the world is not very stable, I can see the far right gaining hold across the globe which is not good news for anyone imo. We are going to have a very dystopian future if we continue as we are and who wants their kids to go through that? But it doesn't take a lot of intelligence to do that, just taking a step back and looking at the bigger picture.
I have never wanted children and I have a degree but whether that is a sign of a high IQ is questionable. Really I am not particularly smart in the great scheme of things, but I can see why not having kids is the intelligent and sensible option.